Modified module composite lamination system, method of use thereof, and

Abstract

The invention relates to a modified modulus composite lamination system, a use method thereof and an aircraft. The modified modulus composite lamination system includes a composite lamination assembly having a layer of structural plies pre-impregnated with a structural resin. The system includes a surface layer applied to the composite laminate assembly and having a modified modulus less than or equal to a ply modulus, a surface layer coefficient of thermal expansion different from a ply coefficient of thermal expansion, and a surface layer coefficient of wet expansion different from a ply coefficient of wet expansion. The system has at least one secondary coating applied to the surface layer. The modification modulus of the surface layer is modified to be greater than or equal to a secondary coating modulus. The surface layer creates stress relief and overall damping between the secondary coating and the structural layer sheet layers, providing enhanced microcracking resistance and minimal structural degradation for the modified modulus composite lamination system.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to composite structure systems and methods, and in particular to co-cured composite laminate structure systems and methods for aircraft composite structures. BACKGROUND

[0002] Composite structures, such as carbon fiber reinforced polymer (or plastic) (CFRP) structures or glass fiber reinforced polymer (or plastic) (GFRP) structures, can be used in a variety of applications, including the manufacture of aircraft, spacecraft, gyroplanes, watercraft, automobiles, trucks, and other vehicles and structures, due to their high strength-to-weight ratio, corrosion resistance, and other excellent properties. Composite structures, such as CFRP or GFRP structures, are typically made of a composite material including a matrix material, such as a resin, reinforced with a fibrous material, such as carbon fiber, glass fiber, aramid fiber, or fiberglass, or other suitable fibrous material. Aircraft composite structures can include aircraft skin panels on wings, vertical and horizontal stabilizers, fuselages, and other aircraft composite structures.

[0003] Known composite structure material systems and methods include composite laminate structures composed of a stack of structural ply layers, each made of a similar material having a similar coefficient of thermal expansion (CTE), a similar coefficient of moisture expansion (CME), and a similar modulus. During manufacture, the composite laminate structure is cured at an elevated temperature, which locks in the thermal induced strain during curing. After curing, a secondary coating, such as paint or primer, is typically applied to the surface of the composite laminate structure at room or ambient temperature. The secondary coating has a different strain, CTE, CME, and modulus than the composite laminate structure, which creates a strain mismatch between the secondary coating and the underlying composite laminate structure. During operation in an environmental setting, during repeated exposure to cyclic thermal and moisture, the thermal and moisture cycles can cause strain and stress and can cause the appearance of undesirable cracking or microcracking in the secondary coating due to the differences in strain, CTE, CME, and modulus between the secondary coating and the underlying composite laminate structure, causing internal cracking or microcracking to propagate into the underlying composite laminate structure. This in turn can cause increased repair or rework costs and can compromise the composite laminate structure.

[0004] Furthermore, known composite structural material systems and methods include modifying the surface of a composite laminate structure mechanically, chemically, or energetically to increase the adhesion of a secondary coating, such as paint or primer, to the surface of the composite laminate structure. However, such known systems and methods only focus on the flexibility (e.g., elongation) of the secondary coating. Moreover, such known systems and methods do not address the modulus modification of the composite laminate structure with respect to the secondary coating or coating applied to the composite laminate structure, as the secondary coating or coating applied to the composite laminate structure is exposed to a large amount of strain and stress, which can cause internal cracking or micro-cracking of the composite laminate structure.

[0005] Moreover, known systems and methods exist that modify the coefficient of thermal expansion between two materials. Such known systems and methods include using a strain isolation pad between the two materials. However, the use of such strain isolation pads utilizes ceramic and metallic materials, and not thermoset composite materials and secondary coatings, such as paint.

[0006] Therefore, there is a need in the art for an improved modulus-modified composite laminate system and method that modifies the modulus of a surface layer on a composite laminate structure to more closely match the modulus of a secondary coating, thereby avoiding strain mismatch, minimizing or preventing surface micro-cracking or cracking in the secondary coating, thereby avoiding repair or rework, minimizing or preventing internal micro-cracking or cracking in the underlying composite laminate structure, thereby avoiding repair or rework, minimizing or preventing structural degradation due to micro-cracking or cracking, improving thermal moisture cycling performance during use, and providing advantages over known composite structural material systems and methods. SUMMARY

[0007] Example embodiments of the present disclosure provide an improved modulus-modified composite laminate system and method. As discussed in detail below, various versions of the improved modulus-modified composite laminate system and method can provide significant advantages over known systems and methods.

[0008] In one version of the present disclosure, an improved modulus-modified composite laminate system is provided. The improved modulus-modified composite laminate system includes a composite laminate assembly that is cured and includes a plurality of structural ply layers pre-impregnated with a structural resin. Each of the structural ply layers has the same ply modulus, ply coefficient of thermal expansion, and ply coefficient of moisture expansion in each of the structural ply layers.

[0009] The modified modulus composite laminate system further includes a surface layer applied directly to the composite laminate assembly, the surface layer being applied prior to cure of the composite laminate assembly or the surface layer being applied after cure of the composite laminate assembly. The surface layer applied prior to cure or applied after cure has a modified modulus less than or equal to the ply modulus, a surface layer coefficient of thermal expansion different from the ply coefficient of thermal expansion, and a surface layer coefficient of moisture expansion different from the ply coefficient of moisture expansion.

[0010] The modified modulus composite laminate system further includes at least one secondary coating applied directly to the surface layer after cure of the composite laminate assembly. The at least one secondary coating has a secondary coating modulus different from the ply modulus, a secondary coating coefficient of thermal expansion different from the ply coefficient of thermal expansion, and a secondary coating coefficient of moisture expansion different from the ply coefficient of moisture expansion.

[0011] Prior to application of the at least one secondary coating to the surface layer, the modified modulus of the surface layer is modified to be greater than or equal to the secondary coating modulus of the at least one secondary coating. When the modified modulus composite laminate system is subjected to one or more of thermal exposure and moisture exposure in a thermal moisture cycle, the surface layer having the modified modulus creates a stress release and overall damping between the at least one secondary coating and the plurality of structural ply layers of the composite laminate assembly, providing enhanced micro-crack resistance and minimized structural degradation for the modified modulus composite laminate system.

[0012] In another version of the disclosure, an aircraft is provided having one or more aircraft composite structures employing a modified modulus composite laminate system. The aircraft includes the one or more aircraft composite structures including one or more of a fuselage, one or more wings, and a tail including one or more vertical stabilizers and horizontal stabilizers.

[0013] The modified modulus composite laminate system integrated in one or more of the aircraft composite structures includes a composite laminate assembly cured and including a plurality of structural ply layers pre-impregnated with a structural resin. Each structural ply layer has a ply modulus, a ply coefficient of thermal expansion, and a ply coefficient of moisture expansion that are the same in each structural ply layer.

[0014] The modified modulus composite laminate system further includes a surface layer applied directly to the composite laminate assembly, the surface layer being applied prior to cure of the composite laminate assembly or the surface layer being applied after cure of the composite laminate assembly. The surface layer applied prior to cure or applied after cure has a modified modulus less than or equal to the ply modulus, a surface layer coefficient of thermal expansion different from the ply coefficient of thermal expansion, and a surface layer coefficient of moisture expansion different from the ply coefficient of moisture expansion.

[0015] The modified modulus composite laminate system further includes at least one secondary coating applied directly to the surface layer after cure of the composite laminate assembly. The at least one secondary coating has a secondary coating modulus different from the ply modulus, a secondary coating coefficient of thermal expansion different from the ply coefficient of thermal expansion, and a secondary coating coefficient of moisture expansion different from the ply coefficient of moisture expansion.

[0016] The modified modulus of the surface layer is modified to be greater than or equal to the secondary coating modulus of the at least one secondary coating prior to application of the at least one secondary coating to the surface layer. The surface layer having the modified modulus creates a stress release and overall damping between the at least one secondary coating and the plurality of structural ply layers of the composite laminate assembly when the one or more aircraft composite structures having the modified modulus composite laminate system are subjected to one or more of thermal exposure and moisture exposure in a thermal moisture cycle, providing enhanced microcrack resistance and minimized structural degradation of the one or more aircraft composite structures having the modified modulus composite laminate system.

[0017] In another version of the disclosure, a method of using a modified modulus composite laminate system is provided to provide enhanced microcrack resistance and minimized structural degradation of a composite structure. The method includes the step of providing the modified modulus composite laminate system.

[0018] The modified modulus composite laminate system includes a composite laminate assembly that is cured and includes a plurality of structural ply layers pre-impregnated with a structural resin. Each structural ply layer has a ply modulus, a ply coefficient of thermal expansion, and a ply coefficient of moisture expansion that are the same in each structural ply layer.

[0019] The modified modulus composite laminate system further includes a surface layer applied directly to the composite laminate assembly, the surface layer being applied prior to cure of the composite laminate assembly or the surface layer being applied after cure of the composite laminate assembly. The surface layer applied prior to cure or applied after cure has a modified modulus less than or equal to the ply modulus, a surface layer coefficient of thermal expansion different from the ply coefficient of thermal expansion, and a surface layer coefficient of moisture expansion different from the ply coefficient of moisture expansion.

[0020] The modified modulus composite laminate system further includes at least one secondary coating applied directly to the surface layer after cure of the composite laminate assembly. The at least one secondary coating has a secondary coating modulus different from the ply modulus, a secondary coating coefficient of thermal expansion different from the ply coefficient of thermal expansion, and a secondary coating coefficient of moisture expansion different from the ply coefficient of moisture expansion. The modified modulus of the surface layer is modified to be greater than or equal to the secondary coating modulus of the at least one secondary coating prior to application of the at least one secondary coating to the surface layer.

[0021] The method further includes the step of integrating the modified modulus composite laminate system in the composite structure. The method further includes the step of using the modified modulus composite laminate system, when the composite structure having the modified modulus composite laminate system is subjected to one or more of thermal exposure and moisture exposure in a thermal moisture cycle, the surface layer having the modified modulus creates a stress relief and overall damping between the at least one secondary coating and the plurality of structural ply layers of the composite laminate assembly, providing enhanced micro-crack resistance and minimized structural degradation of the composite structure having the modified modulus composite laminate system.

[0022] The features, functions, and advantages that have been discussed can be implemented independently in various versions of the disclosure or can be implemented in combination, and more details can be found in the following description and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0023] The disclosure will be better understood with reference to the following detailed description and drawings, which show preferred and example versions, but are not necessarily drawn to scale. The drawings are examples and do not imply a limitation of the specification or claims.

[0024] Figure 1A A block diagram showing an example modified modulus composite laminate system of the disclosure is shown;

[0025] Figure 1B A block diagram showing an example rapid cure process and cured composite structure for a modified modulus composite laminate system of the disclosure is shown;

[0026] Figure 2A A front cross-sectional view of an exemplary modified modulus composite laminate assembly of the present disclosure is shown, with a surface layer in the form of a surface film applied to an uncured composite laminate assembly;

[0027] Figure 2B A front cross-sectional view of the modified modulus composite laminate assembly of Figure 2A is co-cured in an autoclave is shown;

[0028] Figure 2C A front cross-sectional view of an exemplary modified modulus composite laminate system of the present disclosure is shown, with a secondary coating applied to a co-cured Figure 2B modified modulus composite laminate assembly of

[0029] Figure 2D A front cross-sectional view of the modified modulus composite laminate system of Figure 2C is subjected to thermal and moisture exposure is shown;

[0030] Figure 2E A front cross-sectional view of the modified modulus composite laminate system of Figure 2D is shown, with micro-cracks running through the secondary layer and the surface layer;

[0031] Figure 3A A front cross-sectional view of an exemplary modified modulus composite laminate assembly of the present disclosure is shown, with a surface layer in the form of a lightning strike protection material assembly applied to an uncured composite laminate assembly;

[0032] Figure 3B A front cross-sectional view of the modified modulus composite laminate assembly of Figure 3A is co-cured in an autoclave is shown;

[0033] Figure 3C A front cross-sectional view of an exemplary modified modulus composite laminate system of the present disclosure is shown, with a secondary coating applied to a co-cured Figure 3B modified modulus composite laminate assembly of

[0034] Figure 3D A front cross-sectional view of the modified modulus composite laminate system of Figure 3C is subjected to thermal and moisture exposure is shown;

[0035] Figure 3E A front cross-sectional view of the modified modulus composite laminate system of Figure 3D is shown, with micro-cracks running through the secondary layer and the surface layer;

[0036] Figure 4A A front cross-sectional view of an exemplary modified modulus composite laminate system of the present disclosure is shown, of an exemplary uncured composite laminate assembly;

[0037] Figure 4B a front cross-sectional view of a composite laminate assembly of Figure 4A

[0038] Figure 4C a front cross-sectional view of an exemplary modified modulus composite laminate system of the present disclosure, wherein a surface layer in the form of a resin repair layer is applied to a cured Figure 4B

[0039] Figure 4D a front cross-sectional view of a modified modulus composite laminate system of Figure 4C

[0040] Figure 4E a front cross-sectional view of a modified modulus composite laminate system of Figure 4D

[0041] Figure 5 a flowchart illustrating an exemplary version of a method of the present disclosure;

[0042] Figure 6 a perspective view of an aircraft having one or more composite structures incorporating an exemplary modified modulus composite laminate system of the present disclosure;

[0043] Figure 7 a flowchart illustrating an exemplary aircraft manufacturing and service method;

[0044] Figure 8 an exemplary block diagram of an aircraft.

[0045] The drawings shown in the present disclosure represent various aspects of the presented versions, and only the differences will be discussed in detail. DETAILED DESCRIPTION

[0046] The disclosed versions will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all, of the disclosed versions are shown. Indeed, a variety of

[0047] ​​​​This specification includes references to “one version” or “a version.” Instances of the phrase “one version” or “a version” do not necessarily refer to the same version. Particular features, structures, or characteristics can be combined in any suitable manner consistent with the disclosure. All features disclosed in the specification (including the claims, abstract, and drawings) and all steps disclosed in any method or process described herein can be combined in any combination, provided that such features and / or steps are not mutually inconsistent. Each feature disclosed in the specification (including the claims, abstract, and drawings) can be replaced by alternative features serving the same, equivalent, or similar purpose, unless expressly stated otherwise.

[0048] As used herein, the term “includes” is an open term, as used in the claims, that does not exclude additional structures or steps.

[0049] As used herein, “configured to” means that various portions or components can be described or claimed as “configured to” perform one or more tasks. In this context, “configured to” is used to mean that a structure has been manufactured or produced or designed to perform its related task.

[0050] As used herein, the terms “first,” “second,” and the like, are used as labels for nouns that they precede, and do not necessarily describe any type of chronology or order unless explicitly stated otherwise.

[0051] As used herein, elements or steps recited in singular form are understood to include one or more of the elements or steps unless the context clearly dictates otherwise. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. As used herein, the term “combination” is inclusive of combinations that have at least one associated listed item, wherein the combination can further include additional, non-listed items.

[0052] As used herein, the phrase “at least one of’ when used with a list of items indicates that any combination of one or more of the listed items can be used, and that the list is not necessarily exhaustive. In other words, “at least one of’ means that any combination of the items in the list can be used, but not necessarily all of the items in the list. The items can be specific objects, things, or categories.

[0053] Reference is now made to Figures 1A to 1B , Figure 1A A block diagram of an exemplary modified modulus composite lamination system 10 of the present disclosure is shown, and Figure 1BA block diagram illustrating an exemplary surface layer 12 that can be used in the modified modulus composite lamination system 10 of the present disclosure is shown. Figures 1A to 1B The blocks in the diagrams which comprise the flowchart diagrams represent each of the elements, and the lines that connect the various blocks do not imply any particular dependency or order of the elements. Moreover, the connecting lines shown in the various figures presented herein are intended to represent example functional relationships and / or physical couplings between the various elements. It should be noted that many alternatives or additional functional relationships or physical connections can be present in a version of the disclosure, and / or a person of ordinary skill in the art will recognize many alternatives when practicing a version of the disclosure. When implementing illustrative examples in actual practice, one or more of these blocks can be combined, divided, or combined and subdivided into different blocks when Figure 1A The modified modulus composite lamination system 10 in Figure 1B The illustrations of the surface layer 12 in do not imply a physical or architectural limitation of the manner in which illustrative examples can be implemented. Other components, in addition to or in place of those shown, can be used. Some components can be unnecessary.

[0054] Referring now to Figure 1A As shown in Figure 1A , the modified modulus composite lamination system 10 includes a structural assembly 14, such as in the form of a cured or configured to be cured composite laminate assembly (CLA) 16. As shown in Figure 1A , the composite laminate assembly 16 can be in the form of an uncured composite laminate assembly (CLA) 16a, a partially cured composite laminate assembly (CLA) 16b, and / or a cured composite laminate assembly (CLA) 16c. In one exemplary form, as shown in Figure 1A , the structural assembly 14, such as the composite laminate assembly 16, includes a panel 18 (see also Figure 6 ), such as a wing panel 18a (see also Figure 6 ) of a wing 204 (see Figure 6 ) of an aircraft 200a (see Figure 6 ), a fuselage panel 18b of a fuselage 202 (see Figure 6 ) of the aircraft 200a, a horizontal stabilizer (HORIZ. STAB.) panel 18c of a horizontal stabilizer 212 (see Figure 6 ) of the aircraft 200a, a vertical stabilizer (VERT. STAB.) panel 18d of a vertical stabilizer 210 (see Figure 6 ) of the aircraft 200a, or another suitable panel 18 or structural assembly 14.

[0055] The structural assembly 14, such as the composite laminate assembly 16, for example, in the form of the uncured composite laminate assembly 16a, the partially cured composite laminate assembly 16b, and the cured composite laminate assembly 16c, includes a plurality of structural (STRUCT.) layers 20 (see Figure 1A , Figure 2A , Figure 3A Figure 4A ), such as a plurality of structural (STRUCT.) ply layers 22 (see Figure 1A Figure 2A Figure 3A Figure 4A ). Each structural ply layer 22 includes a ply 24 (see Figure 1A Figure 2A Figure 3A Figure 4A ), and the plurality of structural ply layers 22 includes a plurality of plies 24. As shown in Figure 2A Figure 3A Figure 4A , the plurality of plies 24 includes a top ply 24a, a bottom ply 24b, and two (2) middle plies 24c. However, the plurality of plies 24 can include more than two (2) middle plies 24c. As shown in Figure 2A Figure 3A Figure 4A , the plurality of plies 24 takes the form of a structural ply 24d.

[0056] As shown in Figure 1A , each structural ply layer 22 has a modulus 25 (such as a ply modulus 25a), a coefficient of thermal expansion (CTE) 26 (such as a ply coefficient of thermal expansion (CTE) 26a), and a coefficient of moisture expansion (CME) 28 (such as a ply coefficient of moisture expansion (CME) 28a). The ply modulus 25a, the ply CTE 26a, and the ply CME 28a are the same in each structural ply layer 22.

[0057] As further shown in Figure 1A , each structural ply layer 22 has a stress 30 (such as a ply stress 30a) and a strain 32 (such as a ply strain 32a) that occurs during curing 34 (such as in a rapid curing process (PROC.) 35), with heat 36 and temperature 38 rising during a heating time 40. During curing 34, due to the anisotropy of the composite material (COMP. MAT.) 42 of each ply 24 that makes up each structural ply layer 22, the different structural ply layers 22 want to stretch to different sizes relative to each other. However, due to the structural ply layers 22 being bonded together, the stretching is manifested as the stress 30, such as the ply stress 30a.

[0058] As shown in Figure 1A , the plurality of structural layers 20 (such as the plurality of structural ply layers 22) and the plies 24 each include a composite material 42 having structural fibers 44, such as composite (COMP.) fibers 46. As shown in Figure 1A ​​​​​​​​​​​Further shown, the composite material 42 can include one or more of: one or more carbon fiber reinforced polymers (CFRP) 48 or carbon fiber reinforced plastics having carbon fibers 50, one or more glass fiber reinforced polymers (GFRP) 52 or glass fiber reinforced plastics having glass fibers 54 or fiber glass fibers, one or more aramid polymers 56 or aramid plastics having aramid fibers 58, where "aramid" refers to an aromatic polyamide, or another suitable composite material 42 having structural fibers 44 such as composite fibers 46.

[0059] The uncured, partially cured, and cured composite laminate assembly 16 includes a plurality of structural ply layers 22 pre-impregnated with a structural resin (SR) 60 (see Figure 1A , such as a structural prepreg resin. As shown, Figure 1A the structural resin 60 can take the form of an uncured structural resin (SR) 60a, a partially cured structural resin (SR) 60b, and a cured structural resin (SR) 60c.

[0060] The composite material 42 includes a matrix of the structural resin 60 (see Figure 1A ) reinforced with the composite fibers 46. Each structural layer 20, such as each structural ply layer 22, can include a plurality of structural fibers 44, such as composite fibers 46, which can be at least partially, if not entirely, encased within the structural resin 60, the uncured structural resin 60a (see Figure 1A ), the partially cured structural resin 60b (see Figure 1A ), and / or the cured structural resin 60c (see Figure 1A ). Examples of the plurality of structural fibers 44, such as composite fibers 46, include a plurality of carbon fibers 50, a plurality of glass fibers 54 or fiber glass fibers, and / or a plurality of aramid fibers 58, or other suitable structural fibers 44. In a preferred example, the structural layer 20 and / or the structural fibers 44, such as composite fibers 46, are included in and / or arranged in a plurality of structural ply layers 22 having structural plies 24d made of a composite material 42 including a structural resin 60 such as in the form of an uncured structural resin 60a, a partially cured structural resin 60b, and / or a cured structural resin 60c.

[0061] The plurality of structural layers 20 may include a plurality of structural layer sheets 22, the structural layer sheets 22 being made of a composite material 42 comprising a structural resin 60 (such as uncured structural resin 60a). Each of the plurality of structural layers 20 (such as the plurality of structural layer sheets 22) may include a plurality of structural fibers 44 (such as a plurality of composite fibers 46) at least partially encapsulated within the structural resin 60 (such as uncured structural resin 60a, partially cured structural resin 60b, and / or cured structural resin 60c). Each of the plurality of structural layers 20 (such as the plurality of structural layer sheets 22) may include a plurality of carbon fibers 50 at least partially encapsulated within the structural resin 60 (such as uncured structural resin 60a, partially cured structural resin 60b, and / or cured structural resin 60c).

[0062] like Figure 1A As shown, in one version, structural resin (SR) 60 preferably comprises thermosetting structural resin (SR) 62, which includes one or more of the following: epoxy structural resin (SR) 62a, phenolic structural resin (SR) 62b, polyimide structural resin (SR) 62c, bismaleimide structural resin (BMI SR) 62d (such as polybismaleimide structural resin), polyurethane structural resin (SR) 62e, fluoropolymer structural resin (SR) 62f, cyanate ester structural resin (SR) 62g, or another suitable thermosetting structural resin 62. In other versions, structural resin 60 may include and / or include any suitable resin that may have, define, and / or exhibit structural resin viscosity, structural resin curing profile, structural resin rheological properties, structural resin gel point temperature, and / or structural resin gel time.

[0063] like Figure 1A As further shown, the modified modulus composite laminate system 10 further includes one or more surface layers 12, which are applied directly to the structural component 14 (such as the composite laminate component 16). One or more surface layers 12 are either cured 34 (such as co-curing 34a, see [link to documentation]) on the structural component 14 (such as the composite laminate component 16). Figure 1A It can be applied before or after the structural component 14 (such as composite laminate component 16) has cured 34 (such as co-curing 34a).

[0064] like Figure 1A As shown, in one version, one or more surface layers 12 include a surface film 64. The surface film 64 is preferably applied directly to the structural component 14 (such as the composite laminate 16) before curing 34 (such as co-curing 34a) with the structural component 14 (such as the composite laminate 16).

[0065] like Figure 1AAs shown, in another version, one or more surface layers 12 include a lightning strike protection (LSP) material assembly 66. The lightning strike protection material assembly 66 is preferably applied directly to the structural assembly 14 (such as the composite laminate assembly 16) prior to curing 34 (such as co-curing 34a) of the structural assembly 14 (such as the composite laminate assembly 16).

[0066] As shown, in another version, one or more surface layers 12 include a lightning strike protection (LSP) material assembly 66. The lightning strike protection material assembly 66 is preferably applied directly to the structural assembly 14 (such as the composite laminate assembly 16) prior to curing 34 (such as co-curing 34a) of the structural assembly 14 (such as the composite laminate assembly 16). Figure 1A As shown, in another version, one or more surface layers 12 include a lightning strike protection (LSP) material assembly 66. The lightning strike protection material assembly 66 is preferably applied directly to the structural assembly 14 (such as the composite laminate assembly 16) prior to curing 34 (such as co-curing 34a) of the structural assembly 14 (such as the composite laminate assembly 16).

[0067] In other versions, one or more surface layers 12 can include another suitable type of surface layer 12. The following is discussed in connection with Figure 1B One or more surface layers 12, such as surface film 64, lightning strike protection material assembly 66, and one or more resin repair layers 68, are discussed in more detail.

[0068] As shown, modified modulus composite laminate system 10 further includes at least one secondary coating (SC) 70, or multiple coatings, such as at least one secondary coating (SC) layer 70a, or multiple SC layers, applied directly to surface layer 12 (such as first face 150 (see Figure 1A ) or top face 150a (see Figure 2C ) of one or more surface layers 12 after curing 34 of structural assembly 14 (such as composite laminate assembly 16). At least one secondary coating 70 has a modulus 25 (see Figure 2C ) different from ply modulus 25a (such as secondary coating (SC) modulus 25d). Prior to applying at least one secondary coating 70 to surface layer 12, the modified modulus 25c of surface layer 12 is modified to be greater than or equal to the secondary coating modulus 25d of at least one secondary coating 70, such that the surface layer modulus 25b has been modified to obtain modified modulus 25c prior to surface layer 12 being covered with one or more secondary coatings 70. Figure 1A At least one secondary coating 70 further has a coefficient of thermal expansion (CTE) 26 different from ply CTE 26a (such as secondary coating coefficient of thermal expansion (SC CTE) 26c). At least one secondary coating 70 further has a coefficient of moisture expansion (CME) 28 different from ply CME 28a (such as secondary coating coefficient of moisture expansion (SC CME) 28c). At least one secondary coating 70 has a stress 30 (see

[0069] ) when subjected to a thermal moisture (TM) cycle 100 (see Figure 1A ). Figure 1A ), such as a secondary coating (SC) stress 30c (see Figure 1A ), and has a strain 32 (see Figure 1A ), such as a secondary coating (SC) strain 32c (see Figure 1A ).

[0070] As used herein, a “thermal moisture cycle” or “thermal moisture cycle event” refers to a process in which a material is exposed to changes in heat and / or moisture, such as absorbing heat or having thermal exposure, or such as absorbing moisture or having moisture exposure, over the course of its service life, for example, an aircraft moving back and forth between ground standing positions at ambient or elevated temperatures and airborne flight phases at cold or freezing temperatures.

[0071] As shown in Figure 1A , the at least one secondary coating 70 includes one or more of a paint coating 72, a primer coating 72a, a topcoat coating 72b, an underlayer coating 74, a decal 76, a sticker 78, a repair putty coating 80, or another suitable secondary coating 70.

[0072] As shown in Figure 1A , one or more surface layers 12, such as in the form of a surface film 64 and a lightning strike protection material assembly 66, in uncured form, are laid up (such as layup 82) via a layup process 84 on a composite laminate assembly 16, such as an uncured composite laminate assembly 16a, to form a layup assembly (LA) 86. Alternatively, a structural assembly 14, such as a composite laminate assembly 16, for example, an uncured composite laminate assembly 16a, can be laid up on one or more surface layers 12, such as in the form of a surface film 64 or a lightning strike protection material assembly 66.

[0073] As shown in Figure 1A , the layup assembly (LA) 86 can take the form of an uncured layup assembly (LA) 86a, a partially cured layup assembly (LA) 86b, and / or a cured layup assembly (LA) 86c, depending on the stage of curing 34 or co-curing 34a, such as prior to curing 34 or co-curing 34a, during curing 34 or co-curing 34a, or after curing 34 or co-curing 34a, where co-curing cures the layers simultaneously. A layup assembly 86, such as an uncured layup assembly 86a, including a surface layer 12, such as an uncured surface film 64, or an uncured lightning strike protection material assembly 66, laid up on and coupled to an uncured composite laminate assembly 16a, includes a modified modulus composite laminate assembly (ASSY.) 11 (see Figure 1A ).

[0074] In one version, where the surface layer 12 includes one or more resin repair layers 68, the uncured composite laminate assembly 16a is cured to obtain the cured composite laminate assembly 16c, and the surface layer 12 in the form of the one or more resin repair layers 68 is applied to the cured composite laminate assembly 16c after the curing 34.

[0075] For the curing 34, such as the co-curing 34a, the modified modulus composite laminate assembly 11 including the one or more surface layers 12 in the form of the surface film 64 or the lightning strike protection material assembly 66 coupled or attached to the uncured composite laminate assembly 16a at the uncured stage is placed or positioned within a heating device 88 (see Figure 1A , such as an autoclave 90 (see Figure 1A ) or another suitable heating device 88 to undergo the curing 34 (see Figure 1A ) or the co-curing 34a (see Figure 1A ). Preferably, the uncured layup assembly 86a including the surface layer 12, such as the surface film 64 or the lightning strike protection material assembly 66, laid up on the uncured composite laminate assembly 16a and coupled to the uncured composite laminate assembly 16a undergoes a rapid curing process (PROC.) 35 (see Figure 1A ) as disclosed in U.S. Patent No. 11,752,708 B2, the entire contents of which are incorporated herein by reference.

[0076] During the curing 34 or the co-curing 34a in the heating device 88, such as the autoclave 90, the layup assembly 86, such as the uncured layup assembly 86a, including the surface layer 12, such as the uncured surface layer 12a, for example, a surface film 64, such as a resin-based composite surface film 64a (see Figure 1B ), in the form of an uncured prepreg surface film 64b (see Figure 1B ), or for example, a lightning strike protection material assembly 66, such as an uncured lightning strike protection material assembly 66a (see Figure 1B ), laid up on the uncured composite laminate assembly 16a and coupled to the uncured composite laminate assembly 16a, is heated (such as initial heating) at a temperature (TEMP.) 38 (see Figure 1A , such as an initial temperature (TEMP.) 38a (see Figure 1A ), with heat 36 (see Figure 1A , such as an initial heat 36a (see Figure 1A ) to generate a partially cured surface layer 12b (see Figure 1A ) laid up on the partially cured composite laminate assembly 16b (see Figure 1Bsuch as partially cured prepreg surface film 64c (see Figure 1B ), or partially cured lightning strike protection material assembly 66b (see Figure 1B )) of partially cured ply assembly 86b (see Figure 1A ). Initial heat 36a and initial temperature 38a under initial heating is preferably at least 88 °C (88 degrees Celsius, 190 degrees Fahrenheit (°F)), and at most 140 °C (140 degrees Celsius, 284 degrees Fahrenheit (°F)). Initial heating includes initial heating for a heating time 40 (see Figure 1A ), such as initial heating time 40a (see Figure 1A ) of at least 2 (two) minutes, and at most 30 (thirty) minutes. Initial heating under initial heat 36a is sufficient to cause prepreg thermoset resin 118 (see Figure 1B ), such as uncured impregnation resin 136, to become gel 140 (see Figure 1B ), but initial heating under initial heat 36a is insufficient to cause uncured structural resin 60 to become a gel.

[0077] During curing 34 or co-curing 34a in heating apparatus 88 (such as autoclave 90), partially cured surface layer 12b (see Figure 1A ) including ply laid up on and coupled to partially cured composite laminate assembly 16b (see Figure 1B ) such as partially cured prepreg surface film 64c (see Figure 1B ), or partially cured lightning strike protection material assembly 66b (see Figure 1B ) of partially cured ply assembly 86b is then post-heated (such as post-heating) with post heat 36b (see Figure 1A ) at a desired subsequent temperature (TEMP.) 38b (see Figure 1A ) until a final heat 36c (see Figure 1A ) and a final temperature (TEMP.) 38c (see Figure 1A ) greater than initial temperature 38a is reached to generate cured ply assembly 86c (see Figure 1A ) including cured surface layer 12c (see Figure 1B ) such as cured prepreg surface film 64d (see Figure 1B ), or cured lightning strike protection material assembly 66c (see Figure 1B ) laid up on and coupled to cured composite laminate assembly 16c. The combination of initial heating, post-heating, and final heating is sufficient to cure, such as fully cure, both prepreg thermoset resin 118 (such as impregnation resin 136) and structural resin 60.

[0078] The subsequent heating with subsequent heat 36b includes heating for a subsequent heating time 40b (see Figure 1A ) of at least 15 (fifteen) minutes and at most 120 (one hundred twenty) minutes. The final heat 36c (see Figure 1A ) and the final temperature 114c (such as a final cure temperature) under the final heating is preferably at least 120 °C (120 degrees Celsius, 248 degrees Fahrenheit (°F)) and at most 260 °C (260 degrees Celsius, 500 degrees Fahrenheit (°F)). The difference between the final temperature 38c (such as a final cure temperature) and the initial temperature 38a (see Figure 1A ) is at least 20 °C (20 degrees Celsius, 68 degrees Fahrenheit (°F)). The initial heating includes initial heating for an initial heating time 40a, wherein the subsequent heating includes heating for a subsequent heating time 40b, further wherein the difference between the subsequent heating time 40b and the initial heating time 40a is at least 10 (ten) minutes.

[0079] The layup assembly 86 of uncured surface layers 12a (see Figure 1B ) (such as uncured prepreg surface films 64b (see Figure 1B ), or uncured lightning strike protection material assemblies 66a (see Figure 1B )) on uncured composite laminate assemblies 16a (see Figure 1A ) that are laid up on uncured composite laminate assemblies 16a and coupled to uncured surface layers 12a (see Figure 1A ) is cured 34 or co-cured 34a with heat 36 in a heating apparatus 88 (such as an autoclave 90) can further include applying pressure 92 (see ) to at least one of the uncured composite laminate assembly 16a during the initial heating under the initial heat 36a or the partially cured composite laminate assembly 16b during the subsequent heating under the subsequent heat 36b. In some examples, applying pressure 92 includes applying elevated atmospheric (ATM.) pressure 92a of 0 to 150 psi (0 to 150 pounds per square inch) (0 atm (atmospheres) to 10.2 atm (atmospheres)) to the uncured composite laminate assembly 16a and / or the partially cured composite laminate assembly 16b. In some examples, applying pressure 92 includes utilizing the heating apparatus 88 (such as the autoclave 90) to autoclave the uncured composite laminate assembly 16a during the initial heating and / or to autoclave the partially cured composite laminate assembly 16b during the subsequent heating.

[0080] Figure 1AAs shown, after cure 34 or co-cure 34a is complete, or finally, for example, after rapid cure process 35 is complete, the modified modulus composite laminate assembly 11 is in a cured state, and a cured layup assembly 86c is obtained. In this version, one or more secondary coatings 70 are applied to the cured surface layer 12c (see Figure 1B ) that includes the cured prepreg surface film 64d or the cured lightning strike protection material assembly 66c, to obtain the modified modulus composite laminate system 10 (see Figure 1A ). In another version, a surface layer 12 in the form of one or more resin repair layers 68 is applied to the cured composite laminate assembly 16c, and then one or more secondary coatings 70 are applied to the one or more resin repair layers 68.

[0081] As shown in Figure 1A , the modified modulus composite laminate system 10 can be integrated with or can include: a composite structure (STRUC.) (CS) 94 (such as an aircraft composite structure (CS) 94a) in the form of a wing 204 (see Figure 6 ) of an aircraft 200a (see Figure 6 ), a fuselage 202 (see Figure 6 ) of the aircraft 200a, a horizontal stabilizer 212 (see Figure 6 ) of the aircraft 200a, or another suitable composite structure 94 or another suitable aircraft composite structure 94a.

[0082] When the modified modulus composite laminate system 10 and the composite structure 94 (such as the aircraft composite structure 94a) having the modified modulus composite laminate system 10 are subjected to one or more of a thermal exposure 96 (see Figure 1A ) and a moisture exposure 98 (see Figure 1A ) in a thermal moisture cycle 100 (see Figure 1A ), the surface layer 12 having the modified modulus 25c (such as the modified modulus surface layer 12d (see Figure 1B )) produces a stress release 31 (see Figure 1B ) through the thickness of the modified modulus composite laminate system 10, such as a delamination stress release 31a (see Figure 1B ). The surface layer 12 having the modified modulus 25c provides a global dampening 102 (see Figure 1B ) and a global cushioning 104 (see Figure 1B ) between the one or more secondary coatings 70 and the plurality of structural ply layers 22 of the composite laminate assembly 16, further providing the modified modulus composite laminate system 10 and the composite structure 94 (such as the aircraft composite structure 94a) having the modified modulus composite laminate system 10 with enhanced microcrack resistance 106 (see Figure 1A ) and minimized structural degradation 108 (see Figure 1A), and improved hot-wet (TM) cycle performance (PERF.) 110 (see Figure 1A ).

[0083] As the modified modulus composite laminate system 10 and the composite structure 94 having the modified modulus composite laminate system 10, such as the aircraft composite structure 94a, are subjected to the thermal exposure 96 and the moisture exposure 98 of the hot-wet cycle 100, the different materials of the modified modulus composite laminate system 10, such as the plurality of structural ply layers 22 of the composite laminate assembly 16, the one or more surface layers 12 having the modified modulus 25c, and the at least one secondary coating 70 can exhibit different degrees of stretching 112 (see Figure 1A ) such as hot-wet (TM) stretching 112a (see Figure 1A ) and different degrees of shrinking 114 (see Figure 1A ) such as hot-wet (TM) shrinking 114a (see Figure 1A ) exacerbated by the stresses 30 (see Figure 1A ) such as ply stresses 30a, surface layer stresses 30b, and / or secondary coating stresses 30c. Due to the surface layer 12 having the modified modulus 25c or the modified modulus surface layer 12d, there is minimal strain mismatch 32d (see Figure 1A ) between the one or more modified modulus surface layers 12d and the one or more secondary coatings 70, and the modified modulus surface layer 12d safely absorbs the dimensional changes between the modified modulus surface layer 12d and the plies 24 of the underlying structural ply layers 22, resulting in minimized micro-cracking 116 (see Figure 1A , Figure 2E , Figure 3E , Figure 4E ) or cracking and minimizes the formation of micro-cracks or cracks, resulting in enhanced micro-cracking resistance 106 (see Figure 1A ). As a result of the elevated temperature 38 (see Figure 1A ) induced and resulting strain 32 (see FIG. 1) during the curing 34 or co-curing 34a, modifying the modulus 25 of the surface layer 12 to obtain the modified modulus 25c and the modified modulus surface layer 12d creates a stress relief 31 (see Figure 1B ) such as delamination stress relief 31a (see Figure 1B ) throughout the thickness of the modified modulus composite laminate system 10 and between the structural ply layers 22 of the composite laminate assembly 16.

[0084] The stress relief 31 (such as delamination stress relief 31a) throughout the thickness of the modified modulus composite laminate system 10 created by the material design and modification of the modulus 25 of the surface layer 12 provides the improved hot-wet (TM) cycle performance 110 (see Figure 1AThis is measured by the following: very few or no microcracks 116 penetrating the secondary coating 70 and the surface layer 12 (see...). Figure 1A , Figure 2E ), including very few or no surface microcracks (MC) 116a (see Figure 1A , Figure 2E ), and few or no internal microcracks (MC) 116b penetrating and penetrating the structural layer 22 of the composite laminate 16, while maintaining a similar level of adhesion of the secondary coating 70 (e.g., the adhesion of the paint coating 72).

[0085] Now refer to Figure 1B , Figure 1B It shows that it can be used in Figure 1A An exemplary version of one or more surface layers (SL) 12 in the modified modulus composite laminate system 10, wherein one or more surface layers 12 may take the form of an uncured surface layer (SL) 12a, a partially cured surface layer (SL) 12b, and / or a cured surface layer (SL) 12c. One or more surface layers 12 include one or more intermediate layers 12e (see...). Figure 1B One or more intermediate layers 12e are stacked under and between one or more secondary coatings 70 applied on one or more surface layers 12, and are stacked on a plurality of structural sheet layers 22 of the composite laminate assembly 16 located below one or more surface layers 12.

[0086] like Figure 1B As further shown, in one version, surface layer 12 includes and functions as a surface layer (SL) damper 13. When the modified modulus composite laminate system 10 (see...) Figure 1A ) Exposed to heat for 96 (see Figure 1A ) and wet exposure 98 (see Figure 1A When one or more of the following are present, the surface layer damper 13 absorbs at least one secondary coating 70 (see...). Figure 1A ) and composite laminate assembly 16 (see Figure 1A Multiple structural layers 22 (see) Figure 1A Different stresses 30 (see) Figure 1B ) and different strains 32 (see Figure 1B This results in the modified modulus composite laminate system 10 and the composite structure 94 having the modified modulus composite laminate system 10 (see...). Figure 1A (such as aircraft composite structure 94a (see)) Figure 1A Improved thermal and moisture cycling performance 110 (see) Figure 1A ).

[0087] like Figure 1BAs shown, the surface layer 12 (such as each of the one or more surface layers 12) has a modulus 25 (such as a surface layer (SL) modulus 25b) modified to obtain a modified modulus 25c. The modified modulus 25c of the surface layer 12 is less than or equal to the ply modulus 25a of the ply 24. The modified modulus 25c of the surface layer 12 (such as the modified modulus surface layer 12d) is modified to be greater than or equal to the secondary coating modulus 25d of the secondary coating 70 (see Figure 1A ), and obtains a modified modulus surface layer (SL) 12d (see Figure 1B ). For example, if the ply modulus 25a is X, the modified modulus 25c of the surface layer 12 is Y, and the secondary coating modulus 25d is Z, then the relationships are: X is greater than or equal to Y, or Y is less than or equal to X; and Y is greater than or equal to Z, or Z is less than or equal to Y. In one example, the modified modulus 25c of the surface layer 12 is an intermediate modulus between the ply modulus 25a and the secondary coating modulus 25d.

[0088] As further shown in Figure 1B , the surface layer 12 (such as each of the one or more surface layers 12) has a coefficient of thermal expansion (CTE) 26 (see Figure 1A ), such as a surface layer coefficient of thermal expansion (SL CTE) 26b. The surface layer CTE 26b is different than the ply CTE 26a.

[0089] As further shown in Figure 1B , the surface layer 12 (such as each of the one or more surface layers 12) has a coefficient of moisture expansion (CME) 28 (see Figure 1A ), such as a surface layer coefficient of moisture expansion (SL CME) 28b. The surface layer CME is different than the ply CME 28a.

[0090] As further shown in Figure 1B , the surface layer 12 (such as each of the one or more surface layers 12) has or is capable of having a stress 30 (such as a surface layer (SL) stress 30b), and has or is capable of having a strain 32 (such as a surface layer (SL) strain 32b). As described above, when subjected to the thermal exposure 96 (see Figure 1A ) and / or the moisture exposure 98 (see Figure 1A ) of the thermal-moisture cycle 100 (see Figure 1A ), the modified modulus surface layer 12d creates a stress release 31 (see Figure 1B ) through the thickness of the modified modulus composite laminate system 10, such as a delamination stress release 31a (see Figure 1B ).

[0091] As further shown in Figure 1BAs shown, in one version, surface layer 12 (such as each of one or more surface layers 12) may include surface film (SF) 64, such as resin-based composite surface film (SF) 64a (see Figure 1B The surface film 64 may take the form of an uncured prepreg surface film (SF) 64b, a partially cured prepreg surface film (SF) 64c, and / or a cured prepreg surface film (SF) 64d. In other versions, the surface film 64 may comprise a two-component room-temperature miscible epoxy resin impregnated in a carbon or fiberglass or nylon fabric sheet or scrim.

[0092] like Figure 1B As shown, surface film 64 (such as resin-based composite surface film 64a) includes a film layer 65 infused or impregnated with a prepreg thermosetting resin 118. Film layer 65 includes a mesh fabric or carrier containing glass fibers 54 (see [link to documentation]). Figure 1A ) or fiberglass reinforced material, or containing carbon fiber 50 (see Figure 1A The prepreg may be a carbon fiber reinforced material, containing nylon fibers or nylon fiber reinforced material, containing polyester fibers or polyester fiber reinforced material, or containing another suitable fiber reinforced material. The prepreg thermosetting resin 118 includes one or more of the following: adhesive 118a, epoxy resin 118b, phenolic resin 118c, polyimide 118d, bismaleimide (BMI) 118e, polyurethane 118f, fluoropolymer 118g, cyanate ester 118h, or another suitable prepreg thermosetting resin 118. The prepreg thermosetting resin 118 may further include UV-resistant prepreg thermosetting resin, aliphatic epoxy resin prepreg thermosetting resin, flame-retardant prepreg thermosetting resin, or another suitable prepreg thermosetting resin 118.

[0093] like Figure 1B As shown, in one version, surface layer 12 (such as each of one or more surface layers 12) may include a lightning protection material assembly (LSPMA) 66, which is applied directly to and co-cured with the composite laminate assembly 16 prior to curing 34 or co-curing 34a. The lightning protection material assembly 66 provides lightning protection (LSP) 120 to the modified modulus composite laminate system 10 and the composite structure 94 having the modified modulus composite laminate system 10 (such as aircraft composite structure 94a) (see...). Figure 1B ).

[0094] like Figure 1BAs shown, the lightning strike protection material assembly (LSPMA) 66 can take the form of an uncured lightning strike protection material assembly (LSPMA) 66a, a partially cured lightning strike protection material assembly (LSPMA) 66b, and / or a cured lightning strike protection material assembly (LSPMA) 66c. The lightning strike protection material assembly 66 includes a lightning strike intumescent metal foil layer 122 (see Figure 1B ), which includes a lightning strike intumescent metal foil 124 (see Figure 1B ). As shown, Figure 1B the lightning strike intumescent metal foil 124 has a lightning strike protection (LSP) coefficient of thermal expansion (CTE) 26d and a lightning strike protection (LSP) coefficient of moisture expansion (CME) 28d.

[0095] As shown, Figure 1B the lightning strike intumescent metal foil 124 includes a non-continuous metal foil (NON-CONT. MF) 126, which includes one or more of: a perforated metal foil (MF) 126a, a stretched metal foil (MF) 126b, a metal mesh 126c, a metalized fiber mesh 126d, a metal screen 126e, a metalized fiber fabric 126f, a woven metal 126g, a wire mesh 126h, a metal foam 126i, an open cell metal foam 126j, or another suitable non-continuous metal foil 126.

[0096] As shown, Figure 1B the lightning strike intumescent metal foil 124 further includes a metal material 128 or a metal alloy material 130. As further shown, Figure 1B the metal material 128 includes one or more of: copper 128a, aluminum 128b, titanium 128c, nickel 128d, gold 128e, silver 128f, or another suitable metal material 128. As further shown, Figure 1B the metal alloy material 130 includes one or more of: a copper alloy 130a, an aluminum (AL) alloy 130b, a titanium alloy 130c, a nickel alloy 130d, a gold alloy 130e, a silver alloy 130f, a bronze 130g, a brass 130h, or another suitable metal alloy material 130.

[0097] As shown, Figure 1B in one exemplary version, the lightning strike protection material assembly 66 further includes a resin-impregnated scrim layer 132 laminated to the lightning strike intumescent metal foil layer 122. As further shown, Figure 1B the resin-impregnated scrim layer 132 includes a non-metallic scrim 134. As further shown, Figure 1BFurther shown, the non-metallic scrim 134 includes one of a non-metallic scrim mat (SM) 134a, a fiberglass scrim mat (SM) 134b, a carbon fiber scrim mat (SM) 134c, a woven scrim mat (SM) 134d, a knitted polyester scrim mat (SM) 134e, a non-woven scrim mat (SM) 134f, or another suitable non-metallic scrim 134. The non-metallic scrim 134 can further include a scrim fabric or carrier that contains glass fibers 54 (see Figure 1A ) or fiberglass reinforcement, or contains carbon fibers 50 (see Figure 1A ) or carbon fiber reinforcement, contains nylon fibers or nylon fiber reinforcement, contains polyester fibers or polyester fiber reinforcement, or contains another suitable fiber reinforcement.

[0098] As shown in Figure 1B Further shown, the resin-impregnated scrim layer 132 includes a non-metallic scrim 134 that is impregnated with an impregnation resin (IR) 136 (also referred to as a lightning strike protection material resin 138). As shown in Figure 1B , the impregnation resin 136 can take the form of an uncured impregnation resin (IF) 136a, a partially cured impregnation resin (IR) 136b, and / or a cured impregnation resin (IR) 136c. For example, the uncured impregnation resin 136a is in an uncured stage prior to the curing 34 or co-curing 34a, the partially cured impregnation resin 136b is in a partially cured stage during the curing 34 or co-curing 34a, and the cured impregnation resin 136c is in a cured stage after the curing 34 or co-curing 34a. When the impregnation resin 136 is initially heated with the curing 34 or co-curing 34a, the initial heating is sufficient to cause the impregnation resin 136, such as the uncured impregnation resin 136a, to become a gel 140 (see Figure 1A ).

[0099] The impregnation resin 136 includes a prepreg thermoset resin 118 (see Figure 1B ) such as the prepreg thermoset resin 118 of the surface film 64, as shown in Figure 1B The prepreg thermoset resin 118 includes an adhesive 118a, an epoxy resin 118b, a phenolic resin 118c, a polyimide 118d, a bismaleimide (BMI) 118e, a polyurethane 118f, a fluoropolymer 118g, a cyanate ester 118h, or another suitable prepreg thermoset resin 118. The impregnation resin 136 can further include a UV-resistant impregnation resin, an aliphatic epoxy resin impregnation resin, a flame-retardant impregnation resin, or another suitable impregnation resin 136.

[0100] In one version, the impregnation resin 136 has a viscosity (such as a custom viscosity), a cure profile (such as a custom cure profile), and has rheological properties (such as custom rheological properties). As used herein, “custom viscosity” refers to the viscosity of a resin (such as an impregnation resin in a lightning strike protection material assembly) that is related to the lightning strike expanding metal foil and is controlled, adjusted, and selected to be different from the viscosity of a structural resin in a structural assembly (such as a composite laminate assembly) to prevent or minimize mixing of the impregnation resin and the structural resin during co-curing or curing. As used herein, “custom cure profile” refers to a cure profile, such as the number and temperature of optimized cures of a resin (such as an impregnation resin in a lightning strike protection material assembly), that is controlled, adjusted, and selected to be different from the cure profile of a structural resin in a structural assembly (such as a composite laminate assembly) so that the impregnation resin can begin crosslinking at a low temperature to rapidly increase the viscosity of the impregnation resin, allowing the impregnation resin to coat the lightning strike expanding metal foil while maintaining separation and minimizing mixing of the impregnation resin with the structural resin. As used herein, “custom rheological properties” refers to the rheological properties or flow behavior relationship between the viscosity (e.g., gelation and hardening) of a material such as a resin, including an impregnation resin in a lightning strike protection material assembly, and the temperature of the material such as during curing, that is controlled, adjusted, and selected to be different from the rheological properties of a structural resin in a structural assembly (such as a composite laminate assembly) to prevent or minimize mixing of the impregnation resin with the structural resin during co-curing or curing and to provide improved hot wet cycle microcracking resistance of the co-cured composite structure (such as a co-cured composite laminate structure with structural and lightning strike protection components).

[0101] The custom viscosity, custom cure profile, and custom rheological properties of the impregnation resin are related to the lightning strike expanding metal foil 124 and provide chemical compatibility and bonding ability between the impregnation resin 136 and the structural resin 60 (see Figure 1A ) of the structural assembly 14 (such as the composite laminate assembly 16) (e.g., uncured composite laminate assembly 16a (see Figure 1A )) coupled or bonded to the lightning strike protection material assembly 66 (see Figure 1A ).

[0102] The lightning strike protection material assembly 66 is configured for the plies 82 (see Figure 1A ) in the ply-up process 84 (see Figure 1A ) and in one version includes the structural assembly 14 (such as the composite laminate assembly 16) (e.g., uncured composite laminate assembly 16a (see Figure 1A ) of a plurality of structural plies 20 (see Figure 1A ) (such as a plurality of structural ply layers 22 (see Figure 1A) on the lightning strike protection material assembly 66. In one version, the structural resin viscosity, the structural resin cure profile, and the structural resin rheology characteristics of the structural resin 60 are different from the custom viscosity, the custom cure profile, and the custom rheology characteristics of the impregnation resin 136 to prevent mixing of the structural resin 60 and the impregnation resin 136 during the co-cure 34a or cure 34 and to allow the impregnation resin 136 to effectively coat the lightning strike expanding metal foil 124 via the coating 142 (see Figure 1B ) and provide a defined resin boundary 144 (see Figure 1B ). Further, the custom viscosity of the impregnation resin 136 is greater than the structural resin viscosity of the structural resin 60 to prevent mixing of the impregnation resin 136 and the structural resin 60 during the co-cure 34a or cure 34.

[0103] The custom cure profile of the impregnation resin 136 begins crosslinking at the low temperature 38 (see Figure 1A ) to rapidly increase the custom viscosity of the impregnation resin 136, allowing the impregnation resin 136 to effectively coat the lightning strike expanding metal foil 124 via the coating 142 while maintaining separation and minimal mixing of the impregnation resin 136 from the structural resin 60. As used herein, “coat” refers to the impregnation resin (such as a thermoset resin) hardening around the lightning strike expanding metal foil to keep the lightning strike expanding metal foil separate from the structural resin and the composite laminate assembly or structure. For example, during the co-cure 34a or cure 34, the impregnation resin 136 in the non-metallic scrim 134 is forced into the openings of the lightning strike expanding metal foil 124 such that the impregnation resin 136 completely coats or completely surrounds the lightning strike expanding metal foil 124.

[0104] The custom viscosity, the custom cure profile, and the custom rheology characteristics of the impregnation resin 136 are sufficiently different / dissimilar from the structural resin viscosity, the structural resin cure profile, and the structural resin rheology characteristics of the structural resin 60 to ensure that the impregnation resin 136 sufficiently and effectively coats the lightning strike expanding metal foil 124 to provide in-service protection. The impregnation resin 136 has compatible characteristics with the structural resin 60 in the thermal humidity cycling 100 and prevents or minimizes resin mixing of the impregnation resin 136 and the structural resin 60 during the co-cure 34a or cure 34.

[0105] In some versions, the lightning strike protection material assembly 66 can further include one or more additional layers on top of the lightning strike expanding metal foil layer 122. For example, a thin composite prepreg layer, such as the surface film 64 or another suitable layer, can be added and applied on top of the lightning strike expanding metal foil layer 122 to serve as a protective or reinforcing layer on top of the lightning strike expanding metal foil layer 122 to protect the lightning strike expanding metal foil layer 122 during subsequent sanding, painting, polishing, or other post-processing secondary coating procedures.

[0106] As further shown, Figure 1B In yet another version, as further shown, each of the one or more surface layers 12 can include one or more resin repair layers 68 applied directly to the composite laminate assembly 16, such as the cured composite laminate assembly 16c (see Figure 1A ), after curing 34 of the composite laminate assembly 16. In one version, the resin repair layer 68 includes a resin system 146 (see Figure 1B ) having reinforcing composite fibers 46a (see Figure 1B ). The resin system 146 preferably includes a prepreg thermoset resin 118 (see Figure 1B ), such as the prepreg thermoset resin 118 in the surface film 64 and the impregnated resin 136 in the lightning strike protection material assembly 66, where, as further shown, Figure 1B the prepreg thermoset resin 118 includes one or more of the following: a binder 118a, an epoxy resin 118b, a phenolic resin 118c, a polyimide 118d, a bismaleimide (BMI) 118e, a polyurethane 118f, a fluoropolymer 118g, a cyanate ester 118h, or another suitable prepreg thermoset resin 118. The prepreg thermoset resin 118 can further include a UV resistant prepreg thermoset resin, an aliphatic epoxy prepreg thermoset resin, a flame retardant prepreg thermoset resin, or another suitable prepreg thermoset resin 118. In other versions, the resin repair layer 68 can include a two-part temperature-mixable epoxy resin system impregnated into carbon or fiberglass or nylon fabric plies or mesh.

[0107] In another version of the present disclosure, an aircraft 200a (see Figure 1A , Figure 6 ) having one or more aircraft composite structures 94a (see Figure 6 ) is provided, the one or more aircraft composite structures 94a having the modified modulus composite laminate system 10, as described above. The aircraft 200a includes the one or more aircraft composite structures 94a. The one or more aircraft composite structures 94a include one or more of the following: a fuselage 202 (see Figure 6 ), one or more wings 204 (see Figure 6), including one or more vertical stabilizers 210 (see Figure 6 ) and horizontal stabilizers 212 (see Figure 6 ) of a tail 208 (see Figure 6 ) or another suitable aircraft composite structure 94a.

[0108] The modified modulus composite layup system 10 is integrated in one or more aircraft composite structures 94a. The modified modulus composite layup system 10 includes a composite layup assembly 16 that is cured and includes a plurality of structural ply layers 22 pre-impregnated with a structural resin 60. Each structural ply layer 22 has a same ply modulus 25a (see Figure 1A ), a ply coefficient of thermal expansion 26a (see Figure 1A ), and a ply coefficient of moisture expansion 28a (see Figure 1A ) in each structural ply layer 22.

[0109] The modified modulus composite layup system 10 further includes a surface layer 12 applied directly to the composite layup assembly 16 either before the composite layup assembly 16 is cured 34 or co-cured 34a or after the composite layup assembly 16 is cured 34 or co-cured 34a. The surface layer 12 has a modified modulus 25c that is less than or equal to the ply modulus 25a, a surface layer coefficient of thermal expansion 26b that is different than the ply coefficient of thermal expansion 26a, and a surface layer coefficient of moisture expansion 28b that is different than the ply coefficient of moisture expansion 28a.

[0110] The modified modulus composite layup system 10 further includes at least one secondary coating 70 applied directly to the surface layer 12 after the composite layup assembly 16 is cured 34 or co-cured 34a. The at least one secondary coating 70 has a secondary coating modulus 25d (see Figure 1A ) that is different than the ply modulus 25a, a secondary coating coefficient of thermal expansion 26c (see Figure 1A ) that is different than the ply coefficient of thermal expansion 26a, and a secondary coating coefficient of moisture expansion 28c (see Figure 1A ) that is different than the ply coefficient of moisture expansion 28a. As shown in Figure 1A , the at least one secondary coating 70 includes one or more of a paint coating 72, a primer coating 72a, a topcoat coating 72b, an underlayer coating 74, a decal 76, a sticker 78, or a repair putty coating 80.

[0111] The modified modulus 25c of the surface layer 12 is modified to be greater than or equal to the secondary coating modulus 25d of the at least one secondary coating 70 before the at least one secondary coating 70 is applied to the surface layer 12. The surface layer modulus 25b (see Figure 1A) is modified to obtain a modified modulus 25c, where the modified modulus 25c is modified to be greater than or equal to a secondary coating modulus 25d, and the surface layer 12 includes a modified modulus surface layer 12d (see Figure 1B ).

[0112] When one or more aircraft composite structures 94a having the modified modulus composite laminate system 10 are subjected to one or more of a thermal exposure 96 (see Figure 1A ) and a moisture exposure 98 (see Figure 1A ) in a thermal-moisture cycle 100 (see Figure 1A ), the surface layer 12 having the modified modulus 25c, such as the modified modulus surface layer 12d, creates a stress relief 31 (see Figure 1B ) and a bulk damping 102 (see Figure 1B ), and a bulk cushioning 104 (see Figure 1B ) between the at least one secondary coating 70 and the plurality of structural plies 22 of the composite laminate assembly 16, provides enhanced micro-crack resistance 106 (see Figure 1A ) and minimized structural degradation 108 (see Figure 1A ) and increased thermal-moisture cycle performance 110 (see Figure 1A ) for the one or more aircraft composite structures 94a having the modified modulus composite laminate system 10.

[0113] In one version, the modified modulus composite laminate system 10 includes a surface layer 12 that includes a surface film 64 (see Figure 1B ) applied directly to the composite laminate assembly 16 prior to curing 34 or co-curing 34a of the composite laminate assembly 16, and the surface film 64 is cured or co-cured with the composite laminate assembly 16. In one version, the surface film 64 includes a resin-based composite surface film 64a (see Figure 1A ). The surface film 64 can also include another suitable type of surface film 64. The surface film 64 includes a film layer 65 (see Figure 1B ) infused or impregnated with a prepreg thermoset resin 118. As Figure 1B shown, the prepreg thermoset resin 118 includes an adhesive 118a, an epoxy resin 118b, a phenolic resin 118c, a polyimide 118d, a bismaleimide (BMI) 118e, a polyurethane 118f, a fluoropolymer 118g, a cyanate ester 118h, or another suitable prepreg thermoset resin 118. The impregnated resin 136 can further include a UV resistant impregnated resin, an aliphatic epoxy impregnated resin, a fire retardant impregnated resin, or another suitable impregnated resin 136.

[0114] In another version, the modified modulus composite laminate system 10 includes a surface layer 12 that includes a lightning strike protection material assembly 66 (see Figure 1B ) applied directly to the composite laminate assembly 16 prior to curing 34 or co-curing 34a of the composite laminate assembly 16, and the lightning strike protection material assembly 66 is cured or co-cured with the composite laminate assembly 16. In one version, the lightning strike protection material assembly 66 includes a lightning strike expanding metal foil layer 122 (see Figure 1B ) that includes a lightning strike expanding metal foil 124 (see Figure 1B ) and a resin-impregnated scrim layer 132 (see Figure 1B ) laminated to the lightning strike expanding metal foil layer 122. The resin-impregnated scrim layer 132 includes a non-metallic scrim 134 (see Figure 1B ) impregnated with an impregnation resin 136 (see Figure 1B ).

[0115] The lightning strike expanding metal foil 124 includes a discontinuous metal foil 126, such as Figure 1B illustrated, the discontinuous metal foil 126 includes one or more of a perforated metal foil 126a, a stretched metal foil 126b, a metal mesh 126c, a metalized fiber mesh 126d, a metal screen 126e, a metalized fiber fabric 126f, a woven metal 126g, a wire mesh 126h, a metal foam 126i, an open cell metal foam 126j, or another suitable discontinuous metal foil 126.

[0116] The lightning strike expanding metal foil 124 further includes a metal material 128 or a metal alloy material 130. As illustrated, Figure 1B the metal material 128 includes one or more of copper 128a, aluminum 128b, titanium 128c, nickel 128d, gold 128e, silver 128f, or another suitable metal material 128. As illustrated, Figure 1B the metal alloy material 130 includes one or more of a copper alloy 130a, an aluminum (AL) alloy 130b, a titanium alloy 130c, a nickel alloy 130d, a gold alloy 130e, a silver alloy 130f, a bronze 130g, a brass 130h, or another suitable metal alloy material 130.

[0117] As illustrated, Figure 1B the non-metallic scrim 134 includes one or another suitable non-metallic scrim 134 of a non-metallic scrim felt 134a, a fiberglass scrim felt 134b, a carbon fiber scrim felt 134c, a woven scrim felt 134d, a knitted polyester scrim felt 134e, a non-woven scrim felt 134f. The non-metallic scrim 134 can further include a scrim fabric or carrier that contains fiberglass 54 (see Figure 1A ) or fibreglass reinforcement material, or contains carbon fiber 50 (see Figure 1A ) or carbon fiber reinforced materials, contain nylon fibers or nylon fiber reinforced materials, contain polyester fibers or polyester fiber reinforced materials, or contain another suitable fiber reinforced material.

[0118] The infused resin 136 includes a prepreg thermoset resin 118 (see Figure 1B ), such as the prepreg thermoset resin 118 of the surface film 64, as shown in Figure 1B , the prepreg thermoset resin 118 includes an adhesive 118a, an epoxy resin 118b, a phenolic resin 118c, a polyimide 118d, a bismaleimide (BMI) 118e, a polyurethane 118f, a fluoropolymer 118g, a cyanate ester 118h, or another suitable prepreg thermoset resin 118. The infused resin 136 can further include a UV resistant infused resin, an aliphatic epoxy infused resin, a fire retardant infused resin, or another suitable infused resin 136.

[0119] In yet another version, the modified modulus composite lamination system 10 includes a surface layer 12 that includes one or more resin repair layers 68 applied directly to the composite laminate assembly 16 after the composite laminate assembly 16 is cured 34. In one version, the one or more resin repair layers 68 include a resin system 146 having reinforcing composite fibers 46a.

[0120] Referring now to Figures 2A to 2E , Figures 2A to 2E , an exemplary modified modulus composite lamination system 10 (see Figures 2C to 2E ) and an exemplary modified modulus composite laminate assembly 11 (see Figures 2A to 2B ) of the present disclosure are shown, where the surface layer 12 (such as the modified modulus surface layer 12d) takes the form of a surface film 64.

[0121] Referring now to Figure 2A , Figure 2A , a front cross-sectional view of an exemplary modified modulus composite laminate assembly 11 of the present disclosure is shown, including a surface layer 12 (such as an uncured surface layer 12a) that takes the form of a surface film 64 (such as a resin-based composite surface film 64a), applied to a structural assembly 14 (such as a composite laminate assembly 16 that takes the form of an uncured composite laminate assembly 16a) and laid up on the structural assembly 14 to form a layup assembly 86 (such as an uncured layup assembly 86a).

[0122] As shown in Figure 2A , the surface film 64 (such as the resin-based composite surface film 64a) includes a film layer 65 infused or impregnated with a prepreg thermoset resin 118. As shown in Figure 2AFurther shown, the surface film 64, such as the resin-based composite surface film 64a, has a first face 150, such as a top face 150a, a second face 152, such as a bottom face 152a, and an end 154. The surface layer 12, such as the surface film 64, e.g., the resin-based composite surface film 64a, has a modified modulus 25c (see Figure 1B ) and is in the form of a modified modulus surface layer 12d.

[0123] As shown in Figure 2A , the structural assembly 14, such as the composite laminate assembly 16 in the form of the uncured composite laminate assembly 16a, includes a plurality of structural layers 20, such as a plurality of structural ply layers 22, the plurality of structural layers 20 including a plurality of plies 24. Each structural ply layer 22 is pre-impregnated with a structural resin 60, such as in the form of an uncured structural resin 60a, e.g., a thermoset structural resin 62. Figure 2A The structural assembly 14, such as the composite laminate assembly 16, in the form of the panel 18 is shown.

[0124] In one version, as shown in Figure 2A , the structural assembly 14, such as the composite laminate assembly 16, has four (4) structural layers 20, such as four (4) structural ply layers 22, where each structural ply layer 22 includes a ply 24, and the plurality of structural ply layers 22 includes a plurality of plies 24. In other versions, the structural assembly 14, such as the composite laminate assembly 16, can have fewer than four (4) or more than four (4) structural layers 20, such as structural ply layers 22.

[0125] As shown in Figure 2A , the ply 24 includes a top ply 24a, a bottom ply 24b, and two (2) intermediate plies 24c stacked between the bottom ply 24b and the top ply 24a. However, the plurality of plies 24 can include more than two (2) intermediate plies 24c. As shown in Figure 2A , the ply 24 is in the form of a structural ply 24d. Each of the top ply 24a, the bottom ply 24b, and the intermediate ply 24c has a first face 155 (see Figure 2A ), such as a top face 155a (see Figure 2A ), a second face 156 (see Figure 2A ), such as a bottom face 156a (see Figure 2A ), and an end 157 (see Figure 2A ).

[0126] As shown in Figure 2AAs shown, the second face 152 (such as the bottom face 152a) of the surface layer 12 (such as the surface film 64) is laid up on the first face 155 (such as the top face 155a) of the top ply 24a of the plurality of structural ply layers 22 of the structural assembly 14 (such as the composite laminate assembly 16), applied directly thereto, coupled thereto, and in continuous contact therewith.

[0127] Reference is now made to Figure 2B , Figure 2B shown is the interior 158 of the heating device 88 (such as the autoclave 90) during co-curing 34a of the modified modulus composite laminate assembly 11. Figure 2A shown is a front cross-sectional view of the modified modulus composite laminate assembly 11. Figure 2B shown is the layup assembly 86 (such as the partially cured layup assembly 86b) including the surface layer 12 (such as the partially cured surface layer 12b in the form of the surface film 64 (such as the resin-based composite surface film 64a)) applied to and laid up on the structural assembly 14 (such as the composite laminate assembly 16 in the form of the partially cured composite laminate assembly 16b). The surface layer 12 (such as the surface film 64, for example, the resin-based composite surface film 64a) has a modified modulus 25c (see Figure 1B ) and is in the form of the modified modulus surface layer 12d (see Figure 2B ). The structural assembly 14 (such as the composite laminate assembly 16) is in the form of the panel 18 (see Figure 2B ). Figure 2B Further shown is the structural resin 60 (such as in the form of the partially cured structural resin 60b).

[0128] The layup assembly 86 (such as the modified modulus composite laminate assembly 11) is co-cured or cured at the elevated temperature 38 (see Figure 1A ). As shown, Figure 2B due to the anisotropy of the material of the plies 24, the plurality of structural ply layers 22 including different plies 24 (such as the top ply 24a, the bottom ply 24b, and the intermediate ply 24c) want to stretch and contract to different sizes relative to one another. However, the plies 24 are bonded together, so this stretching 112 (see Figure 2B ) and contracting 114 (see Figure 2B ) is manifested as stress 30 (see Figure 2B ). In particular, Figure 2B shown is the stretching 112 and the stress 30 in the intermediate ply 24c adjacent to the bottom ply 24b, and shown is the contracting 114 and the stress 30 in the top ply 24a.

[0129] Reference is now made to Figure 2C , Figure 2CA front cross-sectional view of an exemplary modified modulus composite laminate system 10 of this disclosure is shown, wherein a secondary coating 70 (such as a paint coating 72) is applied to a co-cured or cured composite material. Figure 2B The modified modulus composite laminate assembly 11 includes a layup assembly 86 (such as a cured layup assembly 86c). Figure 2C As shown, the secondary coating 70 (such as paint coating 72) has a first surface 160 (such as top surface 160a), a second surface 162 (such as bottom surface 162a) and an end 164.

[0130] like Figure 2C As shown, a second side 162 (e.g., bottom side 162a) of a secondary coating 70 (such as paint coating 72) is directly applied to and in continuous contact with a first side 150 (e.g., top side 150a) of a surface layer 12 (such as cured surface layer 12c) in the form of a surface film 64 (such as resin-based composite surface film 64a). The surface layer 12 includes an intermediate layer 12e positioned on top of the secondary coating 70 between the surface layer 12 and a structural component 14 (such as a composite laminate 16, e.g., cured composite laminate 16c). The surface layer 12 (such as surface film 64, e.g., resin-based composite surface film 64a) has a modified modulus 25c (see [reference]). Figure 1B And a modified modulus surface layer of 12d was applied (see...) Figure 2C The structural component 14 (such as the composite laminate component 16) takes the form of panel 18 (see...). Figure 2C (in the form of ). Figure 2C Further shown are multiple structural sheet layers 22 comprising multiple sheets 24. Figure 2C Further illustrated is a structural resin 60, such as a cured structural resin 60c.

[0131] Now refer to Figure 2D , Figure 2D The diagram illustrates exposure to heat 96 (such as heat 36) and moisture 98 (such as moisture 165, e.g., rainwater 165a). Figure 2C A front sectional view of the modified modulus composite laminate system 10. (See image.) Figure 2D As shown, the modified modulus composite lamination system 10 includes a secondary coating 70 (such as a paint coating 72) applied to a surface layer 12 (such as a cured surface layer 12c) in the form of a surface film 64 (such as a resin-based composite surface film 64a). The surface layer 12 (such as the surface film 64, for example, the resin-based composite surface film 64a) has a modified modulus 25c (see [reference]). Figure 1B ), and adopts the form of a modified modulus surface layer of 12d. For example... Figure 2DFurther shown, the modified modulus composite laminated system 10 includes a structural assembly 14 (such as a composite laminated assembly 16, e.g., a cured composite laminated assembly 16c) in which the plurality of structural ply layers 22 includes different plies 24, such as top plies 24a, bottom plies 24b, and intermediate plies 24c.

[0132] As Figure 2D Further shown, the structural assembly 14 (such as the composite laminated assembly 16) takes the form of a panel 18, and the modified modulus composite laminated system 10 having the panel 18 is subjected to thermal exposure 96 (such as heat 36) and moisture exposure 98 (such as moisture 165), resulting in some of the plurality of structural ply layers 22 including plies 24 experiencing stretching 112 (such as hot wet stretching 112a), and resulting in some of the plurality of structural ply layers 22 including plies 24 experiencing shrinking 114 (such as hot wet shrinking 114a). Moreover, different materials such as the plies 24, the surface layer 12 (such as the modified modulus surface layer 12d), and the secondary coating 70 exhibit different degrees of stretching 112 (such as hot wet stretching 112a) and different degrees of shrinking 114 (such as hot wet shrinking 114a). This is exacerbated by the stresses 30 (see Figure 2D ). In particular, Figure 2D Shrinking 114 (such as hot wet shrinking 114a) and stresses 30 of the top plies 24a are shown, and stretching 112 (such as hot wet stretching 112a) and stresses 30 of the intermediate plies 24c adjacent the bottom plies 24b are shown.

[0133] Reference is now made to Figure 2E , Figure 2E Shrinking 114 (such as hot wet shrinking 114a) and stresses 30 of the top plies 24a are shown, and stretching 112 (such as hot wet stretching 112a) and stresses 30 of the intermediate plies 24c adjacent the bottom plies 24b are shown. Figure 2D A front cross-sectional view of the modified modulus composite laminated system 10 of Figure 2D is shown, showing micro cracks 116 (such as surface micro cracks 116a) after being subjected to thermal exposure 96 (such as heat 36) and moisture exposure 98 (such as moisture 165, e.g., rain 165a), as Figure 2E shown. As Figure 1B shown, the micro cracks 116 (such as surface micro cracks 116a) extend through the secondary coating 70 (such as the paint coating 72) and the surface layer 12 (such as the cured surface layer 12c) taking the form of a surface film 64 (such as a resin-based composite surface film 64a). The surface layer 12 (such as the surface film 64, e.g., the resin-based composite surface film 64a) has a modified modulus 25c (see

[0134] As Figure 2E Further shown, the modified modulus composite laminated system 10 does not have internal micro cracks 116b (see Figure 1A) and the microcracks 116 do not extend into or through the structural assembly 14, such as a composite laminate assembly 16 in the form of a cured composite laminate assembly 16c, having a plurality of structural ply layers 22 including plies 24 located below the surface layer 12 and the secondary coating 70. As Figure 2E shown, the structural assembly 14, such as the composite laminate assembly 16, is in the form of a panel 18.

[0135] Figure 2E The modified modulus surface layer 12d has a minimum strain mismatch 32d (see Figure 1A ) between the modified modulus surface layer 12d and the secondary coating 70. Figure 2E The modified modulus surface layer 12d of the modified modulus composite laminate system 10 also safely absorbs dimensional changes between the modified modulus surface layer 12d and the structural ply layers 22, whose plies 24 are below or under the modified modulus surface layer 12d, resulting in enhanced microcrack resistance 106 (see Figure 1A ), minimized structural degradation 108 (see Figure 1A ), and improved hot wet cycle performance 110 (see Figure 1A ). In contrast, known structural panels or composite laminates without a modified modulus have a larger strain mismatch between the structural panel or composite laminate and the secondary layer, such as paint, resulting in microcracks or cracks in the structural panel or composite laminate when subjected to hot wet exposure.

[0136] Referring now to Figures 3A to 3E , Figures 3A to 3E , an example modified modulus composite laminate system 10 (see Figures 3C to 3E ) and an example modified modulus composite laminate assembly 11 (see Figures 3A to 3B ) of the present disclosure are shown, where the surface layer 12, such as the modified modulus surface layer 12d, is in the form of a lightning strike protection material assembly 66.

[0137] Referring now to Figure 3A , Figure 3A , a front cross-sectional view of an example modified modulus composite laminate assembly 11 of the present disclosure is shown, including a surface layer 12, such as an uncured surface layer 12a in the form of a lightning strike protection material assembly 66, such as an uncured lightning strike protection material assembly 66a, applied to and laid up on a structural assembly 14, such as a composite laminate assembly 16 in the form of an uncured composite laminate assembly 16a, to form a layup assembly 86, such as an uncured layup assembly 86a.

[0138] As shown in Figure 3A , the lightning strike protection material assembly 66 includes a lightning strike expanding metal foil layer 122, which includes a lightning strike expanding metal foil 124. As Figure 3A Further shown, the lightning strike expanding metal foil layer 122 has a first face 166 (such as a top face 166a), a second face 168 (such as a bottom face 168a), and an end 170. The surface layer 12 (such as the lightning strike protection material assembly 66) has a modified modulus 25c (see Figure 1B ) and is in the form of a modified modulus surface layer 12d.

[0139] As Figure 3A shown, the lightning strike protection material assembly 66 further includes a resin-impregnated scrim layer 132 laminated to the lightning strike expanding metal foil layer 122. The resin-impregnated scrim layer 132 includes a non-metallic scrim 134 impregnated with an impregnation resin 136 (such as a prepreg thermoset resin 118 in the form of an uncured impregnation resin 136a). As Figure 3A Further shown, the resin-impregnated scrim layer 132 has a first face 172 (such as a top face 172a), a second face 174 (such as a bottom face 174a), and an end 176.

[0140] As Figure 3A shown, the second face 168 (such as the bottom face 168a) of the lightning strike expanding metal foil layer 122 is layered on, directly applied to, coupled with, and in continuous contact with the first face 172 (such as the top face 172a) of the resin-impregnated scrim layer 132. As Figure 3A Further shown, the second face 174 (such as the bottom face 174a) of the resin-impregnated scrim layer 132 is layered on, directly applied to, coupled with, and in continuous contact with the first face 155 (such as the top face 155a) of the top ply 24a of the plurality of structural ply layers 22 of the structural assembly 14 (such as the composite laminate assembly 16).

[0141] As Figure 3A shown, the structural assembly 14 (such as the composite laminate assembly 16 in the form of an uncured composite laminate assembly 16a) includes a plurality of structural layers 20 (such as a plurality of structural ply layers 22), the plurality of structural layers 20 including a plurality of plies 24. Each structural ply layer 22 is pre-impregnated with a structural resin 60 (such as a thermoset structural resin 62) in the form of an uncured structural resin 60a. Figure 4A A structural assembly 14 (such as a composite laminate assembly 16) in the form of a panel 18 is shown.

[0142] In one version, as Figure 3AAs shown, structural component 14 (such as composite laminate component 16) has four (4) structural layers 20 (such as four (4) structural layer sheets 22), wherein each structural layer sheet 22 includes a sheet 24, and the plurality of structural layer sheets 22 include a plurality of sheets 24. In other versions, structural component 14 (such as composite laminate component 16) may have fewer than four (4) or more than four (4) structural layers 20 (such as structural layer sheets 22).

[0143] like Figure 3A As further shown, layer 24 includes a top layer 24a, a bottom layer 24b, and two (2) intermediate layers 24c stacked between the bottom layer 24b and the top layer 24a. However, multiple layers 24 may include more than two (2) intermediate layers 24c. Figure 4A As shown, layer 24 takes the form of structural layer 24d. Each of the top layer 24a, bottom layer 24b, and middle layer 24c has a first surface 155 (see...). Figure 4A (such as top surface 155a (see)) Figure 4A )), Page 156 (see page 2) Figure 4A (such as bottom surface 156a (see)) Figure 4A )) and end 157 (see Figure 4A ).

[0144] Now refer to Figure 3B , Figure 3B The image shows the interior 158 of a heating device 88 (such as an autoclave 90) during co-curing 34a. Figure 3A A front cross-sectional view of the modified modulus composite laminate component 11. Figure 3B A layup assembly 86 (such as a partially cured layup assembly 86b) is shown, which includes a surface layer 12 (such as a partially cured surface layer 12b) in the form of a lightning protection material assembly 66 (such as a partially cured lightning protection material assembly 66b). The surface layer 12 (such as a lightning protection material assembly 66) has a modified modulus 25c (see [reference]). Figure 1B And it adopts the form of a modified modulus surface layer of 12d.

[0145] like Figure 3B As shown, the lightning protection material assembly 66 includes: a lightning-expanded metal foil layer 122 including a lightning-expanded metal foil 124; and a resin-impregnated mesh layer 132, which includes a non-metallic mesh 134 impregnated with an impregnating resin 136 (such as a prepreg thermosetting resin 118) in the form of a partially cured impregnating resin 136b. Figure 3BA lightning strike protection material assembly 66 is shown applied to and laid up on a structural assembly 14, such as a composite laminate assembly 16 in the form of a partially cured composite laminate assembly 16b. In particular, a resin-impregnated scrim layer 132 is laid up on a first face 155 (see Figure 3B ) of a top ply 24a of the composite laminate assembly 16, such as a top face 155a (see Figure 3B ). The structural assembly 14, such as the composite laminate assembly 16, is in the form of a panel 18 (see Figure 3B ). Figure 3B Further shown is a structural resin 60, such as in the form of a partially cured structural resin 60b.

[0146] The layup assembly 86, such as the modified modulus composite laminate assembly 11, is co-cured or cured at an elevated temperature 38 (see Figure 1A ). As shown in Figure 4B , due to the anisotropy of the material of the plies 24, the multiple structural ply layers 22 including different plies 24, such as the top ply 24a, the bottom ply 24b, and the intermediate ply 24c, want to stretch and contract to different sizes relative to one another. However, the plies 24 are bonded together, so this stretching 112 (see Figure 4B ) and contracting 114 (see Figure 4B ) manifests as stresses 30 (see Figure 4B ). In particular, Figure 4B stretching 112 and stresses 30 of the intermediate ply 24c adjacent to the bottom ply 24b are shown, and the contracting 114 and stresses 30 of the top ply 24a are shown.

[0147] Referring now to Figure 3C , Figure 3C a front cross-sectional view of an exemplary modified modulus composite laminate system 10 of the present disclosure is shown, in which a secondary coating 70, such as a paint coating 72, is applied to and in direct contact with, coupled to, and in continuous contact with a modified modulus composite laminate assembly 11, such as the co-cured or cured layup assembly 86, such as the cured layup assembly 86c, including Figure 3B . As shown in Figure 3C , the secondary coating 70, such as the paint coating 72, has a first face 160, such as a top face 160a, a second face 162, such as a bottom face 162a, and an end 164.

[0148] As shown in Figure 3C , the second face 162, such as the bottom face 162a, of the secondary coating 70, such as the paint coating 72, is applied directly to, coupled to, and in continuous contact with a first face 166, such as a top face 166a, of a lightning strike expansion metal foil layer 122 of a lightning strike protection material assembly 66, such as the cured lightning strike protection material assembly 66c, and thereon. As shown in Figure 3CAs shown, the lightning protection material assembly 66 includes: a lightning-expanded metal foil layer 122 including a lightning-expanded metal foil 124; and a resin-impregnated mesh layer 132, which includes a non-metallic mesh 134 impregnated with an impregnating resin 136 (such as a prepreg thermosetting resin 118) in the form of a cured impregnating resin 136c.

[0149] In this version, the surface layer 12 (such as a cured surface layer 12c) of the lightning protection material assembly 66 includes an intermediate layer 12e positioned on top of the surface layer 12 between a secondary coating 70 and the structural assembly 14 (such as a composite laminate assembly 16, e.g., a cured composite laminate assembly 16c). The surface layer 12 (such as the lightning protection material assembly 66) has a modified modulus 25c (see [link to relevant documentation]). Figure 1B And a modified modulus surface layer of 12d was applied (see...) Figure 3C The structural component 14 (such as the composite laminate component 16) takes the form of panel 18 (see...). Figure 3C (in the form of ). Figure 3C Further shown are multiple structural sheet layers 22 comprising multiple sheets 24. Figure 3C Further illustrated is a structural resin 60, such as a cured structural resin 60c.

[0150] Figure 3C Further illustrated is a defined resin boundary 144 formed between the resin-impregnated mesh layer 132 of the lightning protection material assembly 66 and the top sheet 24a of the composite laminate assembly 16. The defined resin boundary 144 helps to prevent or minimize mixing of the impregnating resin 136 and the structural resin 60 during co-curing 34a or curing 34.

[0151] Now refer to Figure 3D , Figure 3D The diagram illustrates exposure to heat 96 (such as heat 36) and moisture 98 (such as moisture 165, e.g., rainwater 165a). Figure 3C A front sectional view of the modified modulus composite laminate system 10. (See image.) Figure 3D As shown, the modified modulus composite lamination system 10 includes a secondary coating 70 (such as a paint coating 72) applied to a surface layer 12 (such as a cured surface layer 12c) in the form of a lightning protection material assembly 66 (such as a cured lightning protection material assembly 66c). The surface layer 12 (such as the lightning protection material assembly 66) has a modified modulus 25c (see [reference]). Figure 1B ), and a modified modulus surface layer of 12d was applied (see Figure 3D (in the form of ).

[0152] like Figure 3DAs shown, the lightning strike protection material assembly 66 includes a lightning strike expanded metal foil layer 122 including a lightning strike expanded metal foil 124; and a resin infused scrim layer 132 including a non-metallic scrim 134 infused with an infusion resin 136, such as a prepreg thermoset resin 118, in the form of a cured infusion resin 136c. Figure 3D Further shown is a defined resin boundary 144 formed between the resin infused scrim layer 132 of the lightning strike protection material assembly 66 and the top ply 24a of the composite laminate assembly 16.

[0153] As Figure 3D Further shown, the modified modulus composite laminate system 10 includes a structural assembly 14, such as the composite laminate assembly 16, for example, the cured composite laminate assembly 16c, having a plurality of structural ply layers 22 including different plies 24, such as a top ply 24a, a bottom ply 24b, and an intermediate ply 24c.

[0154] As Figure 3D Further shown, the structural assembly 14, such as the composite laminate assembly 16, is in the form of a panel 18, and the modified modulus composite laminate system 10 having the panel 18 is subjected to a thermal exposure 96, such as heat 36, and a moisture exposure 98, such as moisture 165, resulting in some of the plurality of structural ply layers 22 including the plies 24 experiencing a stretch 112, such as a hot wet stretch 112a, and resulting in some of the plurality of structural ply layers 22 including the plies 24 experiencing a shrinkage 114, such as a hot wet shrinkage 114a. Moreover, different materials, such as the plies 24, the surface layer 12, such as the modified modulus surface layer 12d, and the secondary coating 70, exhibit different degrees of stretch 112, such as hot wet stretch 112a, and different degrees of shrinkage 114, such as hot wet shrinkage 114a. This is exacerbated by the stress 30 (see Figure 3D ). In particular, Figure 3D The shrinkage 114, such as the hot wet shrinkage 114a, and the stress 30 of the top ply 24a are shown, and the stretch 112, such as the hot wet stretch 112a, and the stress 30 of the intermediate ply 24c adjacent to the bottom ply 24b are shown.

[0155] Reference is now made to Figure 3E , Figure 3E A front cross-sectional view of the modified modulus composite laminate system 10 of Figure 3D is shown, showing micro cracks 116, such as surface micro cracks 116a, after being subjected to a thermal exposure 96, such as heat 36, and a moisture exposure 98, such as moisture 165, for example, rain 165a, as shown in Figure 3D . As Figure 3EAs shown, microcracks 116, such as surface microcracks 116a, extend through the secondary coating 70, such as the paint coating 72, and the surface layer 12, such as the cured surface layer 12c, in the form of the lightning strike protection material assembly 66, such as the cured lightning strike protection material assembly 66c. The surface layer 12, such as the lightning strike protection material assembly 66, has a modified modulus 25c (see Figure 1B ), and is in the form of the modified modulus surface layer 12d.

[0156] As shown in Figure 3E , the lightning strike protection material assembly 66 includes a lightning strike expanded metal foil layer 122 including a lightning strike expanded metal foil 124, and a resin-impregnated scrim layer 132 including a non-metallic scrim 134 impregnated with an impregnation resin 136, such as the prepreg thermoset resin 118, in the form of a cured impregnation resin 136c. Figure 3E Further shown is a defined resin boundary 144 formed between the resin-impregnated scrim layer 132 of the lightning strike protection material assembly 66 and the top ply 24a of the composite laminate assembly 16.

[0157] As further shown in Figure 3E , the modified modulus composite laminate system 10 does not have internal microcracks 116b (see Figure 1A ), and the microcracks 116 do not extend to or through the structural assembly 14, such as the composite laminate assembly 16 in the form of the cured composite laminate assembly 16c, having a plurality of structural ply layers 22 including plies 24 located below the surface layer 12 and the secondary coating 70. As shown in Figure 3E , the structural assembly 14, such as the composite laminate assembly 16, is in the form of a panel 18.

[0158] Figure 3E The modified modulus surface layer 12d of the modified modulus composite laminate system 10 of Figure 1A has a minimal strain mismatch 32d (see Figure 3E ) between the modified modulus surface layer 12d and the secondary coating 70. Figure 1A The modified modulus surface layer 12d of the modified modulus composite laminate system 10 of Figure 1A is also able to safely absorb dimensional changes between the modified modulus surface layer 12d and the structural ply layers 22, whose plies 24 are below or under the modified modulus surface layer 12d, resulting in enhanced microcrack resistance 106 (see Figure 1A ), minimized structural degradation 108 (see ), and improved hot wet cycle performance 110 (see

[0159] ). Figures 4A to 4E , Figures 4A to 4E An example modified modulus composite laminate system 10 (see Figures 4C to 4E) and an exemplary structural assembly 14 (such as a composite laminate assembly 16) including an uncured composite laminate assembly 16a, where the surface layer 12 (such as a modified modulus surface layer 12d) takes the form of a resin repair layer 68.

[0160] Reference is now made to Figure 4A , Figure 4A A front cross-sectional view of an exemplary structural assembly 14 (such as a composite laminate assembly 16) is shown, including an uncured composite laminate assembly 16a of an exemplary modified modulus composite lamination system 10 (see Figure 4C ) of the present disclosure.

[0161] As shown Figure 4A , the structural assembly 14 (such as a composite laminate assembly 16) in the form of an uncured composite laminate assembly 16a includes a plurality of structural layers 20 (such as a plurality of structural ply layers 22), the plurality of structural layers 20 including a plurality of plies 24. Each structural ply layer 22 is pre-impregnated with a structural resin 60, such as in the form of an uncured structural resin 60a (e.g., a thermoset structural resin 62). Figure 4A A structural assembly 14 (such as a composite laminate assembly 16) in the form of a panel 18 is shown.

[0162] In one version, as shown Figure 4A , the structural assembly 14 (such as a composite laminate assembly 16) has four (4) structural layers 20, such as four (4) structural ply layers 22, where each structural ply layer 22 includes plies 24 and the plurality of structural ply layers 22 includes a plurality of plies 24. In other versions, the structural assembly 14 (such as a composite laminate assembly 16) can have less than four (4) or more than four (4) structural layers 20 (such as structural ply layers 22).

[0163] As further shown Figure 4A , the plies 24 include a top ply 24a, a bottom ply 24b, and two (2) intermediate plies 24c stacked between the bottom ply 24b and the top ply 24a. However, the plurality of plies 24 can include more than two (2) intermediate plies 24c. As shown Figure 4A , the plies 24 take the form of structural plies 24d. As shown Figure 4A , each of the top ply 24a, the bottom ply 24b, and the intermediate plies 24c has a first face 155 (such as a top face 155a), a second face 156 (such as a bottom face 156a), and an end 157.

[0164] Reference is now made to Figure 4B , Figure 4B A front cross-sectional view of an exemplary modified modulus composite lamination system 10 (see Figure 4C ) of the present disclosure is shown. Figure 4Aa front cross-sectional view of a structural assembly 14 (such as a composite laminate assembly 16 in the form of a partially cured composite laminate assembly 16b) of the Figure 4B composite laminate assembly 16 is shown including a partially cured composite laminate assembly 16b in the form of a panel 18. Figure 4B Further shown is a structural resin 60 such as in the form of a partially cured structural resin 60b.

[0165] During curing 34 (see Figure 4B ), the composite laminate assembly 16 is cured at an elevated temperature 38 (see Figure 1A ). As shown in Figure 4B , due to the anisotropy of the material of the plies 24, the multiple structural ply layers 22 including different plies 24 such as the top plies 24a, the bottom plies 24b, and the middle plies 24c want to stretch and contract to different sizes relative to one another. However, the plies 24 are bonded together, so this stretching 112 (see Figure 4B ) and contracting 114 (see Figure 4B ) manifests as stresses 30 (see Figure 4B ). In particular, Figure 2B stretching 112 and stresses 30 of the middle plies 24c adjacent to the bottom plies 24b are shown, and the contracting 114 and stresses 30 of the top plies 24a are shown.

[0166] Referring now to Figure 4C , Figure 4C a front cross-sectional view of an exemplary modified modulus composite lamination system 10 of the present disclosure is shown, where a surface layer 12 (such as a modified modulus surface layer 12d) in the form of a resin repair layer 68 is applied to a cured Figure 4B structural assembly 14 (such as a composite laminate assembly 16), and now becomes a cured composite laminate assembly 16c. Figure 4C Further shown is a modified modulus composite lamination system 10 having a secondary coating 70 (such as a paint coating 72) applied to the surface layer 12.

[0167] As shown in Figure 4C , the secondary coating 70 (such as a paint coating 72) has a first face 160 (such as a top face 160a), a second face 162 (such as a bottom face 162a), and an end 164. As Figure 4C further shown, the resin repair layer 68 includes a resin system 146 (such as a prepreg thermoset resin 118) having reinforcing composite fibers 46c.

[0168] As Figure 4CAs shown, a second surface 162 (e.g., bottom surface 162a) of a secondary coating 70 (such as paint coating 72) is applied directly to and in continuous contact with a first surface 150 (e.g., top surface 150a) of a surface layer 12 (such as cured surface layer 12c) in the form of a resin repair layer 68. The surface layer 12 includes an intermediate layer 12e positioned on top of the secondary coating 70 between the secondary coating 70 and a structural component 14 (such as a composite laminate 16, e.g., a cured composite laminate 16c). The structural component 14 (such as a composite laminate 16) takes the form of a panel 18 (see...). Figure 2C (in the form of ). Figure 2C Further shown are multiple structural sheet layers 22 comprising multiple sheets 24. Figure 4C Further illustrated is a structural resin 60, such as a cured structural resin 60c.

[0169] Now refer to Figure 4D , Figure 4D The diagram illustrates exposure to heat 96 (such as heat 36) and moisture 98 (such as moisture 165, e.g., rainwater 165a). Figure 4C A front sectional view of the modified modulus composite laminate system 10. (See image.) Figure 4D As shown, the modified modulus composite lamination system 10 includes a secondary coating 70 (such as a paint coating 72) applied to a surface layer 12 (such as a cured surface layer 12c) in the form of a resin repair layer 68. The surface layer 12 (such as the resin repair layer 68) has a modified modulus 25c (see [reference]). Figure 1B ), and a modified modulus surface layer of 12d was applied (see Figure 4D In the form of ) . For example Figure 4D As further shown, the modified modulus composite laminate system 10 includes a structural component 14 (such as a composite laminate component 16, for example, a cured composite laminate component 16c), whose plurality of structural sheet layers 22 include different sheets 24, such as a top sheet 24a, a bottom sheet 24b, and an intermediate sheet 24c.

[0170] like Figure 4D As further shown, structural component 14 (such as composite laminate component 16) takes the form of panel 18, and the modified modulus composite laminate system 10 having panel 18 is subjected to thermal exposure 96 (such as heat 36) and moisture exposure 98 (such as moisture 165), causing some of the multiple structural lamination layers 22 including lamination 24 to undergo stretching 112 (such as thermal and moisture stretching 112a), and causing some of the multiple structural lamination layers 22 including lamination 24 to undergo shrinkage 114 (such as thermal and moisture shrinkage 114a). Furthermore, different materials including lamination 24, surface layer 12 (such as modified modulus surface layer 12d), and secondary coating 70 exhibit varying degrees of stretching 112 (see [reference]). Figure 4D(such as heat and moisture stretching 112a (see)) Figure 4D )) and varying degrees of contraction 114 (see Figure 4D (such as thermal and moisture shrinkage 114a (see)) Figure 4D This is due to stress 30 (see...) Figure 4D This exacerbates the situation. In particular, Figure 4D The shrinkage 114 (such as thermal and moisture shrinkage 114a) and stress 30 of the top sheet 24a are shown, and the tension 112 (such as thermal and moisture tension 112a) and stress 30 of the middle sheet 24c adjacent to the bottom sheet 24b are shown.

[0171] Now refer to Figure 4E , Figure 4E It shows Figure 4D A front cross-sectional view of the modified modulus composite laminate system 10 shows microcracks 116 (such as surface microcracks 116a) after being subjected to thermal exposure 96 (such as heat 36) and moisture exposure 98 (such as moisture 165, e.g., rainwater 165a). Figure 4D As shown. Figure 4E As shown, microcracks 116 (such as surface microcracks 116a) extend through a secondary coating 70 (such as paint coating 72) and a surface layer 12 (such as cured surface layer 12c) in the form of a resin repair layer 68. The surface layer 12 (such as resin repair layer 68) has a modified modulus 25c (see...). Figure 1B ), and adopts the form of a modified modulus surface layer 12d.

[0172] like Figure 4E As further shown, the modified modulus composite laminate system 10 does not have internal microcracks 116b (see [reference]). Figure 1A And the microcracks 116 do not extend into or through the structural component 14 (such as a composite laminate 16 in the form of a cured composite laminate 16c), which has a plurality of structural laminate layers 22 including laminations 24 located beneath the surface layer 12 and the secondary coating 70. Figure 4E As shown, structural component 14 (such as composite laminate component 16) takes the form of panel 18.

[0173] Figure 4E The modified modulus surface layer 12d exhibits minimal strain mismatch 32d between the modified modulus surface layer 12d and the secondary coating 70 (see [reference]). Figure 1A ). Figure 4E The modified modulus surface layer 12d can also safely absorb dimensional changes between the modified modulus surface layer 12d and the structural lamellar layer 22 (whose lamellar layer 24 is below or beneath the modified modulus surface layer 12d), thereby resulting in enhanced resistance to microcracks 106 (see Figure 1A Minimize structural degradation by 108 (see...) Figure 1A ), and improved hot-wet cycle performance 110 (see Figure 1A ). In contrast, known structural panels or composite laminates without a modified modulus have a greater strain mismatch between the structural panel or composite laminate and a secondary layer, such as paint, resulting in microcracking or cracking in the structural panel or composite laminate when subjected to hot-wet exposure.

[0174] Reference is now made to Figure 5 , Figure 5 A flowchart illustrating an exemplary version of the method 190 of the present disclosure is shown. In another version of the present disclosure, the method 190 is provided using the modified modulus composite lamination system 10 (see Figure 1A ) discussed in detail above, to provide a composite structure 94 (see Figure 1A ), such as an aircraft composite structure 94a (see Figure 1A ), with enhanced microcracking resistance 106 (see Figure 1A ) and minimized structural degradation 108 (see Figure 1A ), and improved hot-wet cycle performance 110 (see Figure 1A ). Figure 5 The blocks in the flowchart diagrams represent operations and / or portions or elements thereof, and the lines connecting the various blocks do not imply any particular order or dependency of the operations or portions or elements thereof. Figure 5 The disclosure of the steps of the method 190 and herein should not be interpreted as necessarily determining the order in which the steps are performed. Rather, although an illustrative order is indicated, it is understood that the order of the steps can be modified when appropriate. Thus, certain operations can be performed in different orders or simultaneously.

[0175] As shown in Figure 5 , the method 190 includes the step 192 of providing a modified modulus composite lamination system 10. As described above, the modified modulus composite lamination system 10 includes a structural assembly 14 (see Figure 1A , Figure 2A , Figure 3A , Figure 4A ) that is cured or configured to be cured, such as a composite laminate assembly 16 (see Figure 1A , Figure 2A , Figure 3A , Figure 4A ). As shown in Figure 1A , in one version, the composite laminate assembly 16 takes the form of a panel 18 (see also Figure 6 ), such as a wing panel 18a (see also Figure 6 ), a fuselage panel 18b, a horizontal stabilizer panel 18c, a vertical stabilizer panel 18d, or another suitable panel 18. The composite laminate assembly 16 preferably includes a plurality of structural layers 20 (see Figure 1A , Figure 2A ), such as a plurality of structural ply layers 22 (see Figure 1A , Figure 2A ) pre-impregnated with a structural resin 60 (see Figure 1A , Figure 2A ). Each structural ply layer 22 has a ply modulus 25a (see Figure 1A ), a ply coefficient of thermal expansion (CTE) 26a (see Figure 1A ), and a ply coefficient of moisture expansion (CME) 28a (see Figure 1A ). The ply modulus 25a, the ply CTE 26a, and the ply CME 28a are the same in each structural ply layer 22. Prior to curing 34 (see Figure 1A ) or co-curing 34a (see Figure 1A ), the composite laminate assembly 16 includes an uncured composite laminate assembly (CLA) 16a (see Figure 1A ). During curing 34 or co-curing 34a, the composite laminate assembly 16 includes a partially cured composite laminate assembly (CLA) 16b (see Figure 1A ). After curing 34 or co-curing 34a, the composite laminate assembly 16 includes a cured composite laminate assembly (CLA) 16c (see Figure 1A ).

[0176] The plurality of structural ply layers 22 each include a composite material 42 (see Figure 1A ), as shown in Figure 1A one or more carbon fiber reinforced polymers (CFRP) 48 or carbon fiber reinforced plastics, one or more glass fiber reinforced polymers (GFRP) 52 or glass fiber reinforced plastics, or one or more aramid polymers 56, or another suitable composite material 42. The composite material 42 includes a composite fiber 46 (see Figure 1A ), such as a carbon fiber 50 (see Figure 1A ), a glass fiber 54 (see Figure 1A ), an aramid fiber 58 (see Figure 1A ), or another suitable composite fiber 46. As shown in Figure 1A , the structural resin 60 includes a thermoset structural resin 62 including one or more of an epoxy structural resin 62a, a phenolic structural resin 62b, a polyimide structural resin 62c, a bismaleimide (BMI) structural resin 62d, a polyurethane structural resin 62e, a fluoropolymer structural resin 62f, a cyanate ester structural resin 62g, or another suitable thermoset structural resin 62.

[0177] As described above, the modified modulus composite laminate system 10 further includes a surface layer 12 (see Figures 1A to 1B ), or the surface layer 12 is applied after the composite laminate assembly 16 is cured 34 or co-cured 34a, or the surface layer 12 is applied after the composite laminate assembly 16 is cured 34 or co-cured 34a. The surface layer 12 has a surface layer modulus 25b (see Figure 1B ) modified to obtain a modified modulus 25c (see Figure 1B ) of the surface layer 12d (see Figure 1B ). The modified modulus 25c is less than or equal to the ply modulus 25a. The surface layer 12 further has a surface layer coefficient of thermal expansion (CTE) 26b (see Figure 1B ) different from the ply coefficient of thermal expansion (CTE) 26a. The surface layer 12 further has a surface layer coefficient of moisture expansion (CME) 28b (see Figure 1B ) different from the ply coefficient of moisture expansion (CME) 28a.

[0178] As described above, the modified modulus composite laminate system 10 further includes at least one secondary coating 70 (see Figure 1A ) applied directly to the surface layer 12 after the composite laminate assembly 16 is cured 34 or co-cured 34a, alone or with the surface layer 12. The at least one secondary coating 70 has a secondary coating modulus 25d (see Figure 1A ) different from the ply modulus 25a, has a secondary coating coefficient of thermal expansion (CTE) 26c (see Figure 1A ) different from the ply coefficient of thermal expansion (CTE) 26a, and has a secondary coating coefficient of moisture expansion (CME) (see Figure 1A ) 28c different from the ply coefficient of moisture expansion (CME) 28a. Prior to the at least one secondary coating 70 being applied to the surface layer 12, the modified modulus 25c of the surface layer 12, such as the modified modulus surface layer 12d, is modified to be greater than or equal to the secondary coating modulus 25d of the at least one secondary coating 70, i.e., prior to the secondary coating 70 being applied to the surface layer 12, such as the modified modulus surface layer 12d, the surface layer modulus 25b of the surface layer 12 is modified to obtain the modified modulus 25c of the modified modulus surface layer 12d.

[0179] The step 192 of providing the modified modulus composite laminate system 10 can further include providing the modified modulus composite laminate system 10, wherein the surface layer 12 includes a surface film 64 (see Figure 1B ) applied directly to the composite laminate assembly 16 prior to the composite laminate assembly 16 being cured 34 or co-cured 34a, and the surface film 64 is co-cured or cured with the composite laminate assembly 16 to form the modified modulus composite laminate assembly 11 (see Figure 1A ). In one version, the surface film 64 includes a resin-based composite surface film 64a (see Figure 1B ).

[0180] like Figure 1B As shown, the surface film 64 (such as a resin-based composite surface film 64a) comprises a prepreg thermosetting resin 118, which includes one or more of the following: adhesive 118a, epoxy resin 118b, phenolic resin 118c, polyimide 118d, bismaleimide (BMI) 118e, polyurethane 118f, fluoropolymer 118g, cyanate ester 118h, or another suitable prepreg thermosetting resin 118. The prepreg thermosetting resin 118 may further comprise a UV-resistant prepreg thermosetting resin, an aliphatic epoxy prepreg thermosetting resin, a flame-retardant prepreg thermosetting resin, or another suitable prepreg thermosetting resin 118.

[0181] Step 192 of providing the modified modulus composite laminate system 10 may further include: providing the modified modulus composite laminate system 10, wherein the surface layer 12 includes one or more resin repair layers 68 applied directly to the composite laminate assembly 16 after the composite laminate assembly 16 has cured 34 (see [link to documentation]). Figure 1B In one version, one or more resin repair layers 68 include reinforced composite fibers 46a (see...). Figure 1B ) resin system 146 (see Figure 1B The resin system 146 preferably comprises a prepreg thermosetting resin 118, such as a surface film 64, wherein... Figure 1B As shown, the prepreg thermosetting resin 118 includes one or more of the following: adhesive 118a, epoxy resin 118b, phenolic resin 118c, polyimide 118d, bismaleimide (BMI) 118e, polyurethane 118f, fluoropolymer 118g, cyanate ester 118h, or another suitable prepreg thermosetting resin 118. The prepreg thermosetting resin 118 may further include UV-resistant prepreg thermosetting resin, aliphatic epoxy prepreg thermosetting resin, flame-retardant prepreg thermosetting resin, or another suitable prepreg thermosetting resin 118.

[0182] Step 192 of providing the modified modulus composite laminate system 10 may further include: providing the modified modulus composite laminate system 10, wherein the surface layer 12 includes a lightning protection material component 66 (see [reference]) applied directly to the composite laminate assembly 16 prior to curing 34 or co-curing 34a. Figure 1B The lightning protection material assembly 66 is co-cured with the composite laminate assembly 16. In one version, the lightning protection material assembly 66 includes: a lightning-expanded metal foil 124 (see...). Figure 1B Lightning-induced expansion of the metal foil layer 122 (see...) Figure 1B); and a resin-impregnated scrim layer 132 laminated to the lightning strike expanding metal foil layer 122 (see Figure 1B ). The resin-impregnated scrim layer 132 includes a non-metallic scrim 134 (see Figure 1B ) impregnated with an impregnation resin 136 (see Figure 1B ). As shown in Figure 1B , the non-metallic scrim 134 includes one of a non-metallic scrim mat (SM) 134a, a fiberglass scrim mat (SM) 134b, a carbon fiber scrim mat (SM) 134c, a woven scrim mat (SM) 134d, a knitted polyester scrim mat (SM) 134e, a non-woven scrim mat (SM) 134f, or another suitable non-metallic scrim 134. The non-metallic scrim 134 can further include a scrim fabric or carrier that contains glass fibers 54 (see Figure 1A ) or fiberglass reinforcement material, or contains carbon fibers 50 (see Figure 1A ) or carbon fiber reinforcement material, contains nylon fibers or nylon fiber reinforcement material, contains polyester fibers or polyester fiber reinforcement material, or contains another suitable fiber reinforcement material.

[0183] The step 192 of providing the modified modulus composite laminate system 10 can further include providing the modified modulus composite laminate system 10, wherein, as shown in Figure 1A , the at least one secondary coating 70 includes one or more of a paint coating 72, a primer coating 72a, a topcoat coating 72b, an underlayer coating 74, a decal 76, a sticker 78, a putty coating 80, or another suitable secondary coating 70.

[0184] The step 192 of providing the modified modulus composite laminate system 10 can further include providing the modified modulus composite laminate system 10, wherein the surface layer 12 is applied directly to the composite laminate assembly 16 prior to curing 34 or co-curing 34a of the composite laminate assembly 16, and the surface layer 12 and the composite laminate assembly 16 are co-cured via co-curing 34a (see Figure 1A ) in an autoclave 90 (see Figure 1A , Figure 2B ) with heat 36 (see Figure 1A ) prior to applying the at least one secondary coating 70 to obtain the cured modified modulus composite laminate assembly 11 (see Figure 1A ).

[0185] In this version, the surface layer 12 and the composite laminate assembly 16 undergo a rapid curing process 35 (see Figure 1A ) such as disclosed in U.S. Patent No. 11,752,708 B2, the entire contents of which are incorporated herein by reference. The rapid curing process 35 can further include applying an uncured composite laminate assembly 16a (see Figure 1A , Figure 2A ) initial heating to an initial temperature 38a (see Figure 1A ) to generate a partially cured composite laminate assembly 16b (see Figure 1A ) where the initial heating is sufficient to turn the prepreg thermoset resin 118 (see Figure 1B ) of the un-cured surface film 64 or the impregnated resin 136 of the lightning strike expanding metal foil layer 122 into a gel, but insufficient to turn the un-cured structural resin 60 (see Figure 1A ) into a gel. The rapid curing process 35 can further include: subsequent heating of the partially cured composite laminate assembly 16b to a final temperature 38c (see Figure 1A ) greater than the initial temperature 38a (see Figure 1A ) to generate the cured modified modulus composite laminate assembly 11 (see Figure 1A ) where the combination of the initial heating and the subsequent heating is sufficient to fully cure both the prepreg thermoset resin 118 of the surface film 64 or the impregnated resin 136 of the lightning strike expanding metal foil layer 122 and the structural resin 60. The rapid curing process 35 can further include: applying pressure 92 (see Figure 1A ) such as elevated atmospheric pressure 92a (see Figure 1A ) to at least one of the un-cured composite laminate assembly 16a during the initial heating and the partially cured composite laminate assembly 16b during the subsequent heating.

[0186] As discussed above, as shown in Figure 1B , the lightning strike protection material assembly 66 further includes a metallic material 128 including one or more of copper 128a, aluminum 128b, titanium 128c, nickel 128d, gold 128e, silver 128f, or another suitable metallic material 128; or as shown in Figure 1B , the lightning strike protection material assembly 66 further includes a metallic alloy material 130 including one or more of a copper alloy 130a, an aluminum alloy 130b, a titanium alloy 130c, a nickel alloy 130d, a gold alloy 130e, a silver alloy 130f, a bronze 130g, a brass 130h, or another suitable metallic alloy material.

[0187] As discussed in detail above, the lightning strike protection material assembly 66 further includes a resin-impregnated scrim layer 132 (see Figure 1B , Figure 3A ) laminated to the lightning strike expanding metal foil layer 122. The resin-impregnated scrim layer 132 includes a non-metallic scrim 134 (see Figure 1B ) impregnated with an impregnated resin 136 (see Figure 1BThe impregnating resin 136 has a viscosity (such as a custom viscosity), a curing profile (such as a custom curing profile), and rheological properties (such as custom rheological properties). Figure 1B As shown, the impregnation resin 136 includes a prepreg thermosetting resin 118 (e.g., surface film 64), which includes one or more of the following: adhesive 118a, epoxy resin 118b, phenolic resin 118c, polyimide 118d, bismaleimide (BMI) 118e, polyurethane 118f, fluoropolymer 118g, cyanate ester 118h, or another suitable prepreg thermosetting resin 118.

[0188] like Figure 5 As shown, method 190 further includes step 194: integrating the modified modulus composite lamination system 10 into the composite structure 94 (see...). Figure 1A (such as aircraft composite structure 94a (see)) Figure 1A In the composite structure 94 (such as aircraft composite structure 94a), one of the following may be included: aircraft 200a (see...) Figure 6 The fuselage 202 (see Figure 6 ), Wing 204 of aircraft 200a (see Figure 6 ), Horizontal stabilizer 212 of aircraft 200a (see Figure 6 ) or another suitable composite structure 94 (such as another suitable aircraft composite structure 94a).

[0189] like Figure 5 As shown, method 190 further includes step 196: using a surface layer 12 comprising a modified modulus 25c (such as a modified modulus surface layer 12d (see...) Figure 1B The modified modulus composite laminate system 10 is configured such that when the composite structure 94 having the modified modulus composite laminate system 10 is subjected to thermal and humid cycling 100 (see...) Figure 1A ) or heat exposure during a heat and moisture cycling event 96 (see Figure 1A ) and wet exposure 98 (see Figure 1A When one or more of the following are present, stress relief occurs 31 (see Figure 1B (such as layered stress relief 31a (see)) Figure 1B )) and overall damping 102 (see Figure 1B ) and an integral buffer 104 between at least one secondary coating 70 and the plurality of structural layers 22 of the composite laminate assembly 16 (see Figure 1B This provides enhanced microcrack resistance 106 to the composite structure 94 of the modified modulus composite laminate system 10 (see [link]). Figure 1A ) and minimized structural degradation 108 (see Figure 1A) and improved hot-wet cycle performance 110 (see Figure 1A ).

[0190] In one version, where the surface layer 12 and the composite laminate assembly 16 are co-cured together to form a modified modulus composite laminate assembly 11 (see Figure 1A ), the method 190 can include the following steps, prior to applying the at least one secondary coating 70: providing an uncured (such as an uncured composite laminate assembly 16a (see Figure 1A , Figure 2A )) and including a structural assembly 14 (such as a composite laminate assembly 16) of a plurality of structural ply layers 22 pre-impregnated with a structural resin 60, where each structural ply layer 22 has the same ply modulus 25a, the same ply coefficient of thermal expansion (CTE) 26a, and the same ply coefficient of moisture expansion (CME) 28a; providing a surface layer 12 having a surface layer modulus 25b modified to obtain a modified modulus 25c, a surface layer coefficient of thermal expansion (CTE) 26b different from the ply coefficient of thermal expansion (CTE) 26a, and a surface layer coefficient of moisture expansion (CME) 28b different from the ply coefficient of moisture expansion (CME) 28a; and providing the at least one secondary coating 70 having a secondary coating modulus 25d different from the ply modulus 25a, a secondary coating coefficient of thermal expansion (CTE) 26c different from the ply coefficient of thermal expansion (CTE) 26a, and a secondary coating coefficient of moisture expansion (CME) 28c different from the ply coefficient of moisture expansion (CME) 28a.

[0191] In this version, where the surface layer 12 and the composite laminate assembly 16 are co-cured together to form a modified modulus composite laminate assembly 11 (see Figure 1A ), the method 190 includes the following step, prior to applying the at least one secondary coating 70: modifying the surface layer modulus 25b of the surface layer 12 to be greater than or equal to the secondary coating modulus 25d of the at least one secondary coating 70 to obtain a modified modulus 25c (see Figure 1B ). In this version, the method 190 can further include the following step: laying up 82 (see Figure 1B ) the surface layer 12 having the modified modulus 25c (such as a modified modulus surface layer 12d (see Figure 1A ) on the uncured composite laminate assembly 16a (see Figure 1A ). Alternatively, the uncured composite laminate assembly 16a can be laid up on the surface layer 12 having the modified modulus 25c (such as a modified modulus surface layer 12d).

[0192] In this version, the method 190 can further include the following step: heating 88 (see Figure 1A , Figure 2Bsuch as autoclave 90 (see Figure 1A , Figure 2B )) to cure 34 or co-cure 34a (see Figure 1A ) the surface ply 12 having modified modulus 25c laid up on the uncured composite laminate assembly 16a with heat 36 (see Figure 1A ).

[0193] In this version, the method 190 can further include the step of, after curing 34 or co-curing 34a, applying at least one secondary coating 70 to the surface ply 12 to obtain the modified modulus composite laminate system 10.

[0194] In this version, the method 190 can further include the step of integrating the modified modulus composite laminate system 10 in a composite structure 94, such as an aircraft composite structure 94a. The composite structure 94, such as the aircraft composite structure 94a, can include one of the following: a fuselage 202 (see Figure 6 ) of an aircraft 200a (see Figure 6 ), a wing 204 (see Figure 6 ) of the aircraft 200a, a horizontal stabilizer 212 (see Figure 6 ) of the aircraft 200a, or another suitable composite structure 94, such as another suitable aircraft composite structure 94a.

[0195] In this version, the method 190 can further include the step of using the modified modulus composite laminate system 10 including the surface ply 12 having modified modulus 25c to produce, when the composite structure 94 having the modified modulus composite laminate system 10 is subjected to one or more of a thermal exposure 96 (see Figure 1A ) and / or a moisture exposure 98 (see Figure 1A ) in a thermal-moisture cycling 100 (see Figure 1A ) or a thermal-moisture cycling event, a stress relief 31 (see Figure 1B ) and an overall damping 102 (see Figure 1B ) as well as an overall cushioning 104 (see Figure 1B ) between the at least one secondary coating 70 and the plurality of structural ply layers 22 of the composite laminate assembly 16, providing the composite structure 94 having the modified modulus composite laminate system 10 with enhanced micro-cracking resistance 106 (see Figure 1A ) and minimized structural degradation 108 (see Figure 1A ) as well as improved thermal-moisture cycling performance 110 (see Figure 1A ).

[0196] Reference is now made to Figure 6 , Figure 6A perspective view of a vehicle 200, such as an aircraft 200a, is shown having one or more composite structures 94, such as one or more aircraft composite structures 94a, of an exemplary modified modulus composite lamination system 10 (see also Figure 1A , Figure 2C , Figure 3C , Figure 4C ) integrated therewith. As shown in Figure 6 , the vehicle 200, such as the aircraft 200a, includes a fuselage 202, a wing 204, an engine 206, and a tail 208. As shown in Figure 6 , the tail 208 includes a vertical stabilizer 210 and a horizontal stabilizer 212.

[0197] The modified modulus composite lamination system 10 (see Figure 6 ) has a composite lamination assembly 16 (see Figure 1A ), such as a cured composite lamination assembly 16c (see Figure 1A ), in the form of a panel 18 (see Figure 6 ) of a composite structure 94, such as an aircraft composite structure 94a, for example, the wing 204 (see Figure 6 ), of the aircraft 200a (see Figure 6 ), such as a wing panel 18a (see Figure 6 ). The composite lamination assembly 16, such as the cured composite lamination assembly 16c (see Figure 1A ), of the modified modulus composite lamination system 10 can further include a panel 18 (see Figure 1A ), such as a fuselage panel 18b (see FIG. 1A ) of the fuselage 202, a horizontal stabilizer panel 18c (see FIG. 1A ) of one of the horizontal stabilizers 212, or another suitable panel 18 or structure including or as part of the composite structure 94, such as the aircraft composite structure 94a.

[0198] The composite structure 94, such as the aircraft composite structure 94a, is preferably made of a composite material 42 (see FIG. 1A ), such as a carbon fiber reinforced polymer (CFRP) 48 (see FIG. 1A ) or a carbon fiber reinforced plastic, a glass fiber reinforced polymer (GFRP) 52 (see FIG. 1A ) or a glass fiber reinforced plastic, or an aramid polymer 56 (see FIG. 1A) or another type of composite material 42. The modified modulus composite laminate system 10 including the surface ply 12 having the modified modulus 25c can be integrated into a composite structure 94, such as an aircraft composite structure 94a, having an aerodynamic surface, such as a wing 204, a fuselage 202, a horizontal stabilizer 212, or other aerodynamic surface area of an aircraft 200a, to provide enhanced resistance to microcracking 106 (see FIG. 1A ), minimized structural degradation 108 (see FIG. 1A ), and improved thermal-moisture cycling performance 110 (see FIG. 1A ).

[0199] Although FIG. 6 the aircraft 200a shown therein is generally representative of a commercial passenger aircraft having one or more aircraft composite structures 94a, the teachings of the disclosed versions of the modified modulus composite laminate system 10 (see FIG. 1A ) and the method 190 (see FIG. 5 ) are applicable to aircraft composite structures 94a of other passenger aircraft. Moreover, the teachings of the disclosed versions of the modified modulus composite laminate system 10 (see FIG. 1A ) and the method 190 (see FIG. 5 ) are applicable to aircraft composite structures 94a of cargo aircraft, military aircraft, helicopters, and other types of aircraft or flying vehicles, as well as aerospace vehicles, spacecraft, satellites, space launch vehicles, rockets, and other aerospace vehicles. Furthermore, the teachings of the disclosed versions of the modified modulus composite laminate system 10 (see FIG. 1A ) and the method 190 (see FIG. 5 ) are applicable to composite structures 94, such as marine vessels, automobiles, trains, building structures, or other suitable vehicles or structures.

[0200] Referring now to FIG. 7 and FIG. 8 , FIG. 7 a flowchart of an example aircraft manufacturing and maintenance method 300 is shown, and FIG. 8 an example block diagram of an aircraft 316 is shown. Referring to FIG. 7 and FIG. 8 , the disclosed versions of the present disclosure can be described in the context of the aircraft manufacturing and maintenance method 300 as shown in FIG. 7 and the aircraft 316 as shown in FIG. 8 .

[0201] During pre-production, the exemplary aircraft manufacturing and maintenance method 300 may include the specification and design 302 of the aircraft 316 and material procurement 304. During manufacturing, the production of components and sub-assemblies of the aircraft 316 and system integration 308 are carried out. Thereafter, the aircraft 316 can be certified and delivered 310 for entry into service 312. When in service at a customer's facility 312, the aircraft 316 may be scheduled for routine maintenance and repairs 314 (which may also include modifications, reconfigurations, refurbishments, and other suitable maintenance).

[0202] Each process in the aircraft manufacturing and maintenance method 300 may be performed or implemented by a systems integrator, a third party, and / or an operator (such as a customer). For the purposes of this description, a systems integrator may include, but is not limited to, any number of aircraft manufacturers and major systems subcontractors. A third party may include, but is not limited to, any number of suppliers, subcontractors, and vendors. An operator may include airlines, leasing companies, military entities, service organizations, and other suitable operators.

[0203] like FIG. 8 As shown, an aircraft 316 produced by the exemplary aircraft manufacturing and maintenance method 300 may include a fuselage 318 and an interior 322 having multiple systems 320. Examples of the multiple systems 320 may include one or more of a propulsion system 324, an electrical system 326, a hydraulic system 328, and an environmental system 330. Any number of other systems may be included. While an aerospace example is shown, the principles of this disclosure can be applied to other industries, such as the automotive industry.

[0204] The methods and systems described herein can be used in any or more stages of the aircraft manufacturing and maintenance method 300. For example, a component or sub-component corresponding to component and sub-component manufacturing 306 can be manufactured in a manner similar to that of a component or sub-component produced when the aircraft 316 is in service 312. Additionally, during component and sub-component manufacturing 306 and system integration 308, one or more equipment implementations, method implementations, or combinations thereof can be utilized, for example, to significantly accelerate the assembly of the aircraft 316 or reduce the cost of the aircraft 316. Similarly, when the aircraft 316 is in service 312, for example, but not limited to repair and maintenance 314, one or more equipment implementations, method implementations, or combinations thereof can be utilized.

[0205] Modified Modulus Composite Laminate System 10 (see FIG. 1A ) and Method 190 (see FIG. 5 The public version of ) provides a system and method for reducing surface layer 12 (see FIG. 1A to FIG. 1B ) and secondary coating 70 (see FIG. 1A ) in a heat and humidity cycle of 100 (see FIG. 1A Microcracks 116 during the period (see)FIG. 1A 、 FIG. 2E 、 FIG. 3E 、 FIG. 4E ), and provide enhanced microcracking resistance 106 (see FIG. 1A ) and minimized structural degradation 108 (see FIG. 1A ) and improved hot-wet cycle performance 110 (see FIG. 1A ) for the modified modulus composite laminate system 10 and composite structures 94 (such as aircraft composite structures 94a) having the modified modulus composite laminate system 10. Disclosed versions of the modified modulus composite laminate system 10 (see FIG. 1A ) and method 190 (see FIG. 5 ) include modifying or tailoring the modulus 25 (see FIG. 1A ) of the surface layer 12 (see FIG. 1A to FIG. 1B ) of the top of the structural assembly 14 (such as the composite laminate assembly 16) (see FIG. 1A ) such that the modified modulus 25c (see FIG. 1B ) is modified to be greater than or equal to the secondary coating modulus 25d (see FIG. 1A ). The modified modulus 25c or tailored modulus of the surface layer 12 allows for different tensile 112 (see FIG. 1A ) and shrinkage 114 (see FIG. 1A ) rates between the structural ply layers 22 of the composite laminate assembly 16 and the secondary coating 70 without causing inelastic deformation. The system and method includes evaluating, selecting, designing, and processing each separate material layer across the material thickness to create a stress release 31 (see FIG. 1B ) between the layers due to the thermal induced strain created during curing 34 (see FIG. 1A ) or co-curing 34a (see FIG. 1A ). Further, the tailored method of modifying the modulus 25c of the individual layers (including the surface layer 12 and the low temperature applied secondary coating 70 material) increases the effectiveness of the overall system design to minimize surface microcracking 116a (see FIG. 1A ) and internal microcracking 116b (see FIG. 1A ) and improve hot-wet cycle performance during use. The thermal exposure 96 (see FIG. 1A ) and the wet exposure 98 (see FIG. 1A ) create different strains 32 (see FIG. 1A). By modifying the surface layer modulus 25b of the surface layer 12 during the design of the composite laminate assembly 16 and carefully selecting the secondary coating 70 taking these characteristics into account, the effects of different strains 32 can be safely absorbed, which means reducing or eliminating surface microcracks 116a or internal microcracks 116b. By material design and composite layer modulus modification across the composite thickness, the modified modulus composite laminate system 10 creates stress relief 31 across the thickness of the modified modulus composite laminate system 10 to improve the hot wet cycle performance, as measured by surface microcracks 116a and surface and internal microcracks 116b such as internal microcracks in structural assemblies 14, for example, composite laminate assemblies 16 (see FIG. 1A ), while maintaining near equivalent paint adhesion levels.

[0206] Furthermore, the disclosed versions of the modified modulus composite laminate system 10 (see FIG. 1A ) and the method 190 (see FIG. 5 ) allow for product environmental protection with the secondary coating 70 and minimize structural degradation 108 (see FIG. 1A ) due to internal microcracks 116b, and such minimized structural degradation 108 avoids the need and expense of in-service repairs. The disclosed versions of the modified modulus composite laminate system 10 (see FIG. 1A ) and the method 190 (see FIG. 5 ) further minimize premature product aging damage due to the hot wet cycle 100 (see FIG. 1A ) during use, and can extend the time between paint maintenance or other secondary coating maintenance for the in-service product. The modified modulus surface layer 12d (see FIG. 1B ) has minimal strain mismatch 32d (see FIG. 1A ) between the modified modulus surface layer 12d and the secondary coating 70. The modified modulus surface layer 12d also safely absorbs dimensional changes between the modified modulus surface layer 12d and the structural ply layer 22, whose plies 24 are underneath or below the modified modulus surface layer 12d, resulting in enhanced microcrack resistance 106 (see FIG. 1A ), minimized structural degradation 108 (see FIG. 1A ), and improved hot wet cycle performance 110 (see FIG. 1A ). In contrast, known structural panels or composite laminates without a modified modulus have a greater strain mismatch between the structural panel or composite laminate and the secondary layer, such as paint, resulting in microcracks or cracks in the structural panel or composite laminate when subjected to hot wet exposure.

[0207] Moreover, the modified modulus composite laminate system 10 (see FIG. 1A ) and the method 190 (see FIG. 5the disclosed versions of the modified modulus composite laminate system 10 (see FIG. 1A ) and method 190 (see FIG. 1A ) mitigate, minimize, and / or prevent microcracking 116 and have enhanced microcrack resistance 106 (see FIG. 1A ), and provide minimized structural degradation 108 (see FIG. 1A ) to prevent the degradation from propagating into the underlying composite laminate assembly 16, such as the cured composite laminate assembly 16c (see FIG. 5 ). This avoids costly repairs or rework. Moreover, the disclosed versions of the modified modulus composite laminate system 10 (see FIG. 1A ) and method 190 (see FIG. 5 ) modify the surface layer modulus 25b of the surface layer 12 on the composite laminate assembly 16 to be greater than or equal to the secondary coating modulus 25d of the secondary coating 70 applied to the surface layer 12 to avoid strain mismatch, minimize or prevent surface microcracking 116a or cracking of the secondary coating 70, thereby avoiding repairs or rework, to minimize or prevent internal microcracking 116b or cracking of the underlying composite laminate assembly 16, thereby avoiding repairs or rework, to minimize structural degradation due to microcracking 116 or cracking, to improve hot wet cycle performance during use, and to allow different rates of stretching 112 and shrinking 114 between the structural ply layers 22 of the composite laminate assembly 16 and the secondary coating 70, and provide advantages over known composite structural material systems and methods. Moreover, the disclosed versions of the modified modulus composite laminate system 10 (see FIG. 2A to FIG. 2E ) and method 190 (see FIG. 3A to FIG. 3E ) allow for various versions of the one or more surface layers 12, in one version where the one or more surface layers 12 include a surface film 64 (see FIG. 4A to FIG. 4E ), in another version where the one or more surface layers 12 include a lightning strike protection material assembly 66 (see

[0208] Many modifications and other versions of the disclosure will come to mind of one skilled in the art upon considering the teachings presented herein and the associated drawings. The versions described herein are intended to be illustrative and not exhaustive. Although specific terms are employed per the description, they are used in a generic and descriptive sense only and not for purposes of limitation. Methods and devices within the scope of the disclosure are possible in light of the description above. Such modifications and variations are intended to fall within the scope of the appended claims. The disclosure is limited only by the terms of the claims and the full scope of equivalents for which the claims are entitled. The claims are intended to cover all modifications and alternatives of the disclosure.

[0209] Cross Reference to Related Applications

[0210] This non-provisional patent application is also related to concurrently filed U.S. Non-Provisional Patent Application Serial No. 18 / 776,160, filed July 17, 2024, entitled “LIGHTNING STRIKE PROTECTION MATERIAL ASSEMBLY, SYSTEM, AND METHOD OF USING THE SAME,” attorney docket number 23-1752-US-NP, the entire contents of which are incorporated herein by reference. By reference in the cross-reference section of this related application, the application having attorney docket number 23-1752-US-NP is not considered prior art to the subject application having attorney docket number 23-1815-US-NP.

[0211] Examples of the present disclosure can be described in terms of one or more of the following clauses.

[0212] Clause 1. A modified modulus composite laminate system, the modified modulus composite laminate system comprising:

[0213] a composite laminate assembly, the composite laminate assembly being cured and comprising a plurality of structural ply layers pre-impregnated with a structural resin, each structural ply layer having a ply modulus, a ply coefficient of thermal expansion, and a ply coefficient of moisture expansion that are the same in each structural ply layer;

[0214] a surface layer applied directly to the composite laminate assembly, the surface layer being applied prior to curing of the composite laminate assembly or the surface layer being applied after curing of the composite laminate assembly, the surface layer as applied prior to the curing or as applied after the curing having a modified modulus that is less than or equal to the ply modulus, a surface layer coefficient of thermal expansion that is different from the ply coefficient of thermal expansion, and a surface layer coefficient of moisture expansion that is different from the ply coefficient of moisture expansion; and

[0215] at least one secondary coating applied directly to the surface layer after curing of the composite laminate assembly, the at least one secondary coating having a secondary coating modulus that is different from the ply modulus, a secondary coating coefficient of thermal expansion that is different from the ply coefficient of thermal expansion, and a secondary coating coefficient of moisture expansion that is different from the ply coefficient of moisture expansion,

[0216] wherein the modified modulus of the surface layer is modified to be greater than or equal to the secondary coating modulus of the at least one secondary coating prior to applying the at least one secondary coating to the surface layer, and

[0217] Further wherein, when the modified modulus composite laminate system is subjected to one or more of thermal exposure and moisture exposure in a thermal-moisture cycle, the surface layer having the modified modulus creates stress relief and bulk damping between the at least one secondary coating and the plurality of structural plies of the composite laminate assembly, providing the modified modulus composite laminate system with enhanced resistance to microcracking and minimized structural degradation.

[0218] Clause 2. The modified modulus composite laminate system of Clause 1, wherein the plurality of structural ply layers each comprise a composite material comprising one of: one or more carbon fiber reinforced polymers, one or more glass fiber reinforced polymers, or one or more aramid polymers.

[0219] Clause 3. The modified modulus composite laminate system of Clause 1, wherein the surface layer comprises a surface film applied directly to the composite laminate assembly prior to curing of the composite laminate assembly and co-cured with the composite laminate assembly, the surface film comprising a resin-based composite surface film.

[0220] Clause 4. The modified modulus composite laminate system of Clause 3, wherein the resin-based composite surface film comprises a prepreg thermoset resin comprising one or more of: an adhesive, an epoxy resin, a phenolic resin, a polyimide, a bismaleimide, a polyurethane, a fluoropolymer, and a cyanate ester.

[0221] Clause 5. The modified modulus composite laminate system of Clause 1, wherein the surface layer comprises a lightning strike protection material assembly applied directly to the composite laminate assembly prior to curing of the composite laminate assembly and co-cured with the composite laminate assembly, the lightning strike protection material assembly comprising:

[0222] a lightning strike expanding metal foil layer comprising a lightning strike expanding metal foil; and

[0223] a resin-impregnated scrim layer laminated to the lightning strike expanding metal foil layer, the resin-impregnated scrim layer comprising a non-metallic scrim impregnated with an impregnation resin.

[0224] Clause 6. The modified modulus composite laminate system of Clause 5, wherein the lightning strike expanding metal foil comprises a non-continuous metal foil comprising one or more of: a perforated metal foil, a stretched metal foil, a metal mesh, a metalized fiber mesh, a metal screen, a metalized fiber fabric, a woven metal, a wire mesh, a metal foam, and an open cell metal foam.

[0225] Clause 7. The modified modulus composite laminate system of Clause 5, wherein the non-metallic scrim comprises one of: a non-metallic scrim mat, a fiberglass scrim mat, a carbon fiber scrim mat, a woven scrim mat, a knitted polyester scrim mat, or a non-woven scrim mat.

[0226] Clause 8. The modified modulus composite laminate system of Clause 1, wherein the surface layer comprises one or more resin repair layers applied directly to the composite laminate assembly after the composite laminate assembly is cured, each of the one or more resin repair layers comprising a resin system having reinforcing composite fibers.

[0227] Clause 9. The modified modulus composite laminate system of Clause 1, wherein the at least one secondary coating comprises one or more of: a paint coating, a primer coating, a topcoat coating, a basecoat coating, a decal, a sticker, or a putty coating.

[0228] Clause 10. The modified modulus composite laminate system of Clause 1, wherein the surface layer comprises a surface layer damper that absorbs different stresses and different strains of the at least one secondary coating to each of the plurality of structural ply layers of the composite laminate assembly when the modified modulus composite laminate system is subjected to one or more of the thermal exposure and the moisture exposure, resulting in improved hot-wet cycle performance of the modified modulus composite laminate system.

[0229] Clause 11. An aircraft having one or more aircraft composite structures employing a modified modulus composite laminate system, the aircraft comprising:

[0230] the one or more aircraft composite structures comprising one or more of:

[0231] a fuselage;

[0232] one or more wings; and

[0233] a tail comprising one or more vertical stabilizers and horizontal stabilizers; and

[0234] the modified modulus composite laminate system integrated in the one or more aircraft composite structures, the modified modulus composite laminate system comprising:

[0235] a composite laminate assembly cured and comprising a plurality of structural ply layers pre-impregnated with a structural resin, each structural ply layer having a same ply modulus, a same ply coefficient of thermal expansion, and a same ply coefficient of moisture expansion in each structural ply layer;

[0236] a surface layer, the surface layer being applied directly to the composite laminate assembly, the surface layer being applied prior to cure of the composite laminate assembly or the surface layer being applied after cure of the composite laminate assembly, the surface layer having a modified modulus less than or equal to the ply modulus, a surface layer coefficient of thermal expansion different from the ply coefficient of thermal expansion, and a surface layer coefficient of moisture expansion different from the ply coefficient of moisture expansion; and

[0237] at least one secondary coating, the at least one secondary coating being applied directly to the surface layer after cure of the composite laminate assembly, the at least one secondary coating having a secondary coating modulus different from the ply modulus, a secondary coating coefficient of thermal expansion different from the ply coefficient of thermal expansion, and a secondary coating coefficient of moisture expansion different from the ply coefficient of moisture expansion,

[0238] wherein, prior to application of the at least one secondary coating to the surface layer, the modified modulus of the surface layer is modified to be greater than or equal to the secondary coating modulus of the at least one secondary coating, and further wherein, when the one or more aircraft composite structures having the modified modulus composite laminate system are subjected to one or more of thermal exposure and moisture exposure in a thermal-moisture cycle, the surface layer having the modified modulus creates a stress relief and overall damping between the at least one secondary coating and the plurality of structural ply layers of the composite laminate assembly, providing enhanced resistance to microcracking and minimized structural degradation of the one or more aircraft composite structures having the modified modulus composite laminate system.

[0239] Clause 12. The aircraft of Clause 11, wherein the surface layer comprises a surface film, the surface film being applied directly to the composite laminate assembly prior to cure of the composite laminate assembly and co-cured with the composite laminate assembly, the surface film comprising a resin-based composite surface film.

[0240] Clause 13. The aircraft of Clause 11, wherein the surface layer comprises a lightning strike protection material assembly, the lightning strike protection material assembly being applied directly to the composite laminate assembly prior to cure of the composite laminate assembly and co-cured with the composite laminate assembly, the lightning strike protection material assembly comprising:

[0241] a lightning strike expanding metal foil layer, the lightning strike expanding metal foil layer comprising a lightning strike expanding metal foil; and

[0242] a resin-impregnated scrim layer, the resin-impregnated scrim layer being laminated to the lightning strike expanding metal foil layer, the resin-impregnated scrim layer comprising a non-metallic scrim having an impregnated resin.

[0243] Clause 14. The aircraft of Clause 11, wherein the surface layer includes one or more resin repair layers applied directly to the composite laminate assembly after the composite laminate assembly is cured, the resin repair layers each including a resin system having reinforcing composite fibers.

[0244] Clause 15. The aircraft of Clause 11, wherein the at least one secondary coating includes one or more of a paint coating, a primer coating, a topcoat coating, a basecoat coating, a decal, a sticker, or a putty coating.

[0245] Clause 16. A method of using a modified modulus composite laminate system to provide enhanced microcrack resistance and minimized structural degradation for a composite structure, the method comprising the steps of:

[0246] providing the modified modulus composite laminate system, the modified modulus composite laminate system comprising:

[0247] a composite laminate assembly cured and including a plurality of structural ply layers pre-impregnated with a structural resin, each structural ply layer having a same ply modulus, a ply coefficient of thermal expansion, and a ply coefficient of moisture expansion in each structural ply layer;

[0248] a surface layer applied directly to the composite laminate assembly, the surface layer applied prior to curing of the composite laminate assembly or the surface layer applied after curing of the composite laminate assembly, the surface layer applied prior to curing or the surface layer applied after curing having a modified modulus less than or equal to the ply modulus, a surface layer coefficient of thermal expansion different from the ply coefficient of thermal expansion, and a surface layer coefficient of moisture expansion different from the ply coefficient of moisture expansion; and

[0249] at least one secondary coating applied directly to the surface layer after curing of the composite laminate assembly, the at least one secondary coating having a secondary coating modulus different from the ply modulus, a secondary coating coefficient of thermal expansion different from the ply coefficient of thermal expansion, and a secondary coating coefficient of moisture expansion different from the ply coefficient of moisture expansion, wherein the modified modulus of the surface layer is modified to be greater than or equal to the secondary coating modulus of the at least one secondary coating prior to applying the at least one secondary coating to the surface layer;

[0250] integrating the modified modulus composite laminate system in the composite structure; and

[0251] The use of the modified modulus composite laminate system provides the enhanced resistance to microcracking and the minimized structural degradation of the composite structure having the modified modulus composite laminate system when the composite structure having the modified modulus composite laminate system is subjected to one or more of thermal exposure and moisture exposure in a hot wet cycle.

[0252] Clause 17. The method of clause 16, wherein the step of providing the modified modulus composite laminate system further comprises the step of providing the modified modulus composite laminate system, wherein the surface layer comprises one of:

[0253] a surface film applied directly to the composite laminate assembly prior to cure of the composite laminate assembly and co-cured with the composite laminate assembly, the surface film comprising a resin-based composite surface film;

[0254] one or more resinous repair layers applied directly to the composite laminate assembly after cure of the composite laminate assembly, the resinous repair layers each comprising a resin system with reinforcing composite fibers; or

[0255] a lightning strike protection material assembly applied directly to the composite laminate assembly prior to cure of the composite laminate assembly and co-cured with the composite laminate assembly, the lightning strike protection material assembly comprising:

[0256] a lightning strike expanding metal foil layer comprising a lightning strike expanding metal foil; and

[0257] a resin-impregnated scrim layer laminated to the lightning strike expanding metal foil layer, the resin-impregnated scrim layer comprising a non-metallic scrim with impregnated resin.

[0258] Clause 18. The method of clause 16, wherein the step of providing the modified modulus composite laminate system further comprises the step of providing the modified modulus composite laminate system, wherein the at least one secondary coating layer comprises one or more of: a paint coating layer, a primer coating layer, a topcoat coating layer, an underlayer coating layer, a decal, a sticker, or a repair putty coating layer.

[0259] Clause 19. The method of clause 16, wherein the step of providing the modified modulus composite laminate system further comprises the step of providing the modified modulus composite laminate system, wherein the surface layer is applied directly to the composite laminate assembly prior to curing of the composite laminate assembly, and the surface layer is co-cured with the composite laminate assembly in an autoclave with heat prior to application of the at least one secondary coating to obtain a cured modified modulus composite laminate assembly.

[0260] Clause 20. The method of clause 16, wherein the step of integrating the modified modulus composite laminate system in the composite structure further comprises the step of integrating the modified modulus composite laminate system in the composite structure, the composite structure comprising one of:

[0261] a fuselage of an aircraft;

[0262] a wing of the aircraft; or

[0263] a horizontal stabilizer of the aircraft.

Claims

1. A modified modulus composite lamination system, the modified modulus composite lamination system comprising: A composite laminate assembly, the composite laminate assembly being cured and comprising a plurality of structural laminations pre-impregnated with structural resin, each structural lamination having the same lamination modulus, lamination coefficient of thermal expansion and lamination coefficient of wet expansion in each structural lamination; A surface layer, which is applied directly to the composite laminate assembly, is applied either before or after the composite laminate assembly is cured, wherein the surface layer applied before or after curing has a modified modulus less than or equal to the lamination modulus, a surface layer thermal expansion coefficient different from the lamination thermal expansion coefficient, and a surface layer wet expansion coefficient different from the lamination wet expansion coefficient; as well as At least one secondary coating is applied directly to the surface layer after the composite laminate assembly has cured. The at least one secondary coating has a secondary coating modulus different from the lamination modulus, a secondary coating coefficient of thermal expansion different from the lamination coefficient of thermal expansion, and a secondary coating coefficient of wet expansion different from the lamination coefficient of wet expansion. Specifically, before applying the at least one secondary coating to the surface layer, the modified modulus of the surface layer is modified to be greater than or equal to the secondary coating modulus of the at least one secondary coating, and Furthermore, when the modified modulus composite laminate system is subjected to one or more of thermal and wet exposures in a thermal-humidity cycle, the surface layer having the modified modulus generates stress relief and overall damping between the at least one secondary coating and the plurality of structural layers of the composite laminate assembly, providing the modified modulus composite laminate system with enhanced resistance to microcracks and minimized structural degradation.

2. The modified modulus composite lamination system according to claim 1, wherein, Each of the plurality of structural layers comprises a composite material, which includes one of the following: one or more carbon fiber reinforced polymers, one or more glass fiber reinforced polymers, or one or more aramid polymers.

3. The modified modulus composite lamination system according to claim 1, wherein, The surface layer includes a surface film, which is applied directly to the composite laminate before the composite laminate is cured, and the surface film is co-cured with the composite laminate. The surface film includes a resin-based composite surface film.

4. The modified modulus composite laminate system according to claim 3, wherein, The resin-based composite surface film comprises a prepreg thermosetting resin, which includes one or more of the following: adhesives, epoxy resins, phenolic resins, polyimides, bismaleimides, polyurethanes, fluoropolymers, and cyanate esters.

5. The modified modulus composite laminate system according to claim 1, wherein, The surface layer includes a lightning protection material component. Before the composite laminate is cured, the lightning protection material component is directly applied to the composite laminate, and the lightning protection material component is co-cured with the composite laminate. The lightning protection material component includes: A lightning-expanded metal foil layer, the lightning-expanded metal foil layer comprising a lightning-expanded metal foil; and A resin-impregnated mesh fabric layer is laminated onto the lightning-expanded metal foil layer, wherein the resin-impregnated mesh fabric layer comprises a non-metallic mesh fabric impregnated with impregnating resin.

6. The modified modulus composite laminate system according to claim 5, wherein, The lightning-expanded metal foil includes discontinuous metal foil, which includes one or more of the following: perforated metal foil, stretched metal foil, metal mesh, metallized fiber mesh, metal screen, metallized fiber fabric, woven metal, wire mesh, metal foam, and open-cell metal foam.

7. The modified modulus composite laminate system according to claim 5, wherein, The non-metallic mesh fabric includes one of the following: non-metallic mesh fabric felt, glass fiber mesh fabric felt, carbon fiber mesh fabric felt, woven mesh fabric felt, knitted polyester mesh fabric felt, or non-woven mesh fabric felt.

8. The modified modulus composite laminate system according to claim 1, wherein, The surface layer includes one or more resin repair layers, which are applied directly to the composite laminate after the composite laminate has cured. Each of the one or more resin repair layers includes a resin system with reinforcing composite fibers.

9. An aircraft having one or more aircraft composite structures employing a modified modulus composite lamination system, the aircraft comprising: The one or more aircraft composite structures, wherein the one or more aircraft composite structures include one or more of the following: body; One or more wings; as well as Tail fin, said tail fin including one or more vertical stabilizers and horizontal stabilizers; and The modified modulus composite laminate system, integrated in one or more aircraft composite structures, comprises: A composite laminate assembly, the composite laminate assembly being cured and comprising a plurality of structural laminations pre-impregnated with structural resin, each structural lamination having the same lamination modulus, lamination coefficient of thermal expansion and lamination coefficient of wet expansion in each structural lamination; A surface layer, said surface layer being directly applied to the composite laminate assembly, said surface layer being applied before the composite laminate assembly is cured, or said surface layer being applied after the composite laminate assembly is cured, wherein said surface layer, whether applied before or after curing, has a modified modulus less than or equal to said lamination modulus, a surface layer thermal expansion coefficient different from said lamination thermal expansion coefficient, and a surface layer wet expansion coefficient different from said lamination wet expansion coefficient; and At least one secondary coating is applied directly to the surface layer after the composite laminate assembly has cured. The at least one secondary coating has a secondary coating modulus different from the lamination modulus, a secondary coating coefficient of thermal expansion different from the lamination coefficient of thermal expansion, and a secondary coating coefficient of wet expansion different from the lamination coefficient of wet expansion. Specifically, before applying the at least one secondary coating to the surface layer, the modified modulus of the surface layer is modified to be greater than or equal to the secondary coating modulus of the at least one secondary coating, and Furthermore, when the one or more aircraft composite structures having the modified modulus composite lamination system are subjected to one or more of thermal and wet exposures in a thermal-humidity cycle, the surface layer having the modified modulus generates stress relief and overall damping between the at least one secondary coating and the plurality of structural layers of the composite lamination assembly, providing enhanced resistance to microcracks and minimized structural degradation for the one or more aircraft composite structures having the modified modulus composite lamination system.

10. A method for providing enhanced microcrack resistance and minimized structural degradation to a composite structure using a modified modulus composite lamination system, the method comprising the steps of: The modified modulus composite lamination system is provided, the modified modulus composite lamination system comprising: A composite laminate assembly, the composite laminate assembly being cured and comprising a plurality of structural laminations pre-impregnated with structural resin, each structural lamination having the same lamination modulus, lamination coefficient of thermal expansion and lamination coefficient of wet expansion in each structural lamination; A surface layer, said surface layer being directly applied to the composite laminate assembly, said surface layer being applied before the composite laminate assembly is cured, or said surface layer being applied after the composite laminate assembly is cured, wherein said surface layer, whether applied before or after curing, has a modified modulus less than or equal to said lamination modulus, a surface layer thermal expansion coefficient different from said lamination thermal expansion coefficient, and a surface layer wet expansion coefficient different from said lamination wet expansion coefficient; and At least one secondary coating is applied directly to the surface layer after the composite laminate assembly has cured. The at least one secondary coating has a secondary coating modulus different from the lamination modulus, a secondary coating coefficient of thermal expansion different from the lamination coefficient of thermal expansion, and a secondary coating coefficient of wet expansion different from the lamination coefficient of wet expansion. Before applying the at least one secondary coating to the surface layer, the modified modulus of the surface layer is modified to be greater than or equal to the secondary coating modulus of the at least one secondary coating. Integrating the modified modulus composite laminate system into the composite structure; and Using the modified modulus composite laminate system, when the composite structure having the modified modulus composite laminate system is subjected to one or more of thermal and wet exposures in a thermal and wet cycle, the surface layer having the modified modulus causes stress release and overall damping between the at least one secondary coating and the plurality of structural layers of the composite laminate assembly, providing the composite structure having the modified modulus composite laminate system with the enhanced resistance to microcracks and the minimized structural degradation.

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