Method for manufacturing a composite article and composite article manufactured thereby

Abstract

The present disclosure relates to a method for producing a composite article, and the composite article produced thereby. The method described herein utilizes a curable composition that includes an NCF fabric having a particular type of suture. The curable composition and composite article produced according to the present disclosure are particularly suitable for producing composite parts for use in many applications, such as aeronautical, automotive, and marine applications.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 63 / 210,168, filed June 14, 2021, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a method for producing a composite article, and the composite article produced thereby. The method described herein utilizes a curable composition that includes an NCF fabric having a particular type of suture. The curable composition and composite article produced according to the present disclosure are particularly suitable for producing composite parts for use in many applications, such as aeronautical, automotive, and marine applications. [Background technology]

[0003] Fiber-reinforced polymer ("FRP") composites are being promoted as modern alternatives to more traditional materials in a variety of applications, such as the aircraft, automotive, marine, industrial, and infrastructure / building sectors. Specifically, FRP composites can be used as replacements for metals and alloys, such as steel and aluminum, and as replacements for concrete, depending on the application.

[0004] The impetus for FRP composites can be attributed to a variety of factors, including the need for alternatives to metals and lightweight materials with a balance of desirable properties that may include toughness and chemical resistance. More specifically, reducing the overall weight while maintaining or even enhancing the desirable properties of FRP composites can eliminate issues associated with metal fatigue and corrosion, resulting in more fuel-efficient aircraft, automobiles, transportation vehicles, and ships, and their parts, without sacrificing performance. Furthermore, by fabricating aircraft, vehicle, and ship parts and components using FRP composites, not only can the overall weight of the aircraft, vehicle, and ship be reduced, but the time required to manufacture and fabricate the parts and components can also be reduced. Similarly, for construction and infrastructure applications, FRP composites can provide an alternative to traditional building and construction materials while reducing and maintaining the overall cost, weight (and associated stresses and loads), and time required to build (i.e., through prefabrication processes) of the structure.

[0005] To produce FRP composites, reinforcing fibers, which may be provided in a variety of forms, such as non-crimped fibers, are combined with a matrix resin. This combination is then cured, typically in a mold, at a given temperature and pressure to form the final FRP composite. However, the resulting FRP composites may lack the strength and toughness desired for certain applications, particularly aircraft applications.

[0006] Non-crimping fabrics (NCFs) typically comprise one or more layers of structural fibers, filaments, or yarns, each layer having fibers, filaments, or yarns oriented in a different direction. The fibers, filaments, or yarns are also referred to as reinforcing fibers, filaments, or yarns. Such non-crimping fabrics may further comprise one or more interlayers, each of which may comprise, for example, a web, fabric, veil, scrim, or the like. The layers are typically held together by stitching.

[0007] Composite parts, such as NCF composites, are often subjected to thermal cycles and periods of high humidity when used in various applications. Due to temperature changes, such composite parts experience expansion and contraction in different directions depending on the coefficient of thermal expansion (CTE) of the plies, which depends on their orientation. If the expansion or contraction is carefully performed on independent and stress-free plies, no stress will be generated regardless of the orientation of the plies. However, when plies are rotated in different orientations and stacked together, the stresses in the adjacent plies prevent each ply from expanding or contracting according to its own CTE. This results in high stresses in the plies. Microcracks typically form in the matrix because the matrix has a lower in-situ fracture stress than the fibers. Furthermore, it is known that the introduction of stitches, which are typically used to secure the plies together, can result in the formation of areas in the vicinity of the stitches that are prone to the formation of microcracks as a result of the expansion or contraction of the plies. Microcracks can cause significant changes in properties such as stiffness. Mitigating the formation of microcracks is therefore a research issue in the field.

[0008] No. 9,695,533 to Beraud et al. and U.S. Patent No. 8,613,257 to Wockatz describe strategies to minimize the size of resin-rich regions in composite parts by reducing suture fineness to improve the microcracking behavior of the composite and the in-plane mechanical properties of the composite, respectively. However, the improvements in microcracking behavior described are not sufficient for certain applications.

[0009] Thus, there is a continuing need to mitigate or prevent the onset of microcracking in composite parts exposed to hygrothermal stresses, particularly parts made from NCFs. Described herein is a new strategy for inhibiting microcracking behavior in composite articles, in which certain curable compositions are cured according to the methods of the present invention. Summary of the Invention

[0010] This objective, as well as other objectives that will become apparent from the following detailed description, are met in whole or in part by the compositions, methods and / or processes of the present disclosure.

[0011] In a first aspect, the present disclosure relates to a method of making a composite article, the method comprising: a) providing a curable composition comprising a matrix resin and a non-crimped fabric, the non-crimped fabric comprising at least one layer of unidirectionally oriented multifilament carbon yarns and a multifilament suture interconnecting the multifilament carbon yarns, the suture comprising a thermoplastic polymer and having a linear density of 80 dtex or less; b) Curable composition at temperature T 1 Heating to T 1 is the melting temperature of the suture (T m ) and T m Or T 1 a conversion of matrix resin in the range of 30% or less, typically 20% or less, more typically 10% or less; c) at a temperature T for a time sufficient to cure the curable composition. 1 or maintain temperature T 2 heating to a temperature of 100° C., thereby producing a composite article; Includes.

[0012] In a second aspect, the present disclosure relates to a composite article produced according to the methods described herein. [Brief description of the drawings]

[0013] [Figure 1] 1 shows accelerated hygrothermal loading representative of operating conditions typical of the life cycle of a subsonic jet. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] As used herein, the terms "a," "an," or "the" mean "one or more" or "at least one," and can be used interchangeably, unless otherwise stated.

[0015] As used herein, the term "and / or" used in a phrase of the form "A and / or B" means A only, B only, or A and B together.

[0016] As used herein, the term "comprises" includes "consists essentially of" and "consists of." The term "comprising" includes "consisting essentially of" and "consisting of."

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0018] As used herein, unless otherwise indicated, the term "about" or "approximately" refers to an acceptable error for a particular value as determined by one of ordinary skill in the art, which depends in part on how the value is measured or determined. In certain embodiments, the term "about" or "approximately" refers to within 1, 2, 3, or 4 standard deviations. In certain embodiments, the term "about" or "approximately" refers to within 50%, 20%, 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, or 0.05% of a given value or range.

[0019] It will also be understood that any numerical ranges described herein are intended to include all subranges subsumed therein. For example, the range "1 to 10" is intended to include all subranges between and including the recited minimum of 1 and the recited maximum of 10, i.e., having a minimum of 1 or more and a maximum of 10 or less. The disclosed numerical ranges are continuous, and therefore include all values ​​between the minimum and maximum. Unless otherwise indicated, the various numerical ranges specified in this application are approximations.

[0020] Throughout this disclosure, various publications may be incorporated by reference. If the meaning of any language in such a publication incorporated by reference conflicts with the meaning of the language in this disclosure, the meaning of the language in this disclosure shall control unless otherwise indicated.

[0021] In a first aspect, the present disclosure relates to a method of making a composite article, the method comprising: a) providing a curable composition comprising a matrix resin and a non-crimped fabric, the non-crimped fabric comprising at least one layer of unidirectionally oriented multifilament carbon yarns and a multifilament suture interconnecting the multifilament carbon yarns, the suture comprising a thermoplastic polymer and having a linear density of 80 dtex or less; b) Curable composition at temperature T 1 Heating to T 1 is the melting temperature of the suture (T m ) and T m Or T 1 the conversion of the curable composition in is 30% or less, typically 20% or less, more typically 10% or less; and c) at a temperature T for a time sufficient to cure the curable composition. 1 or maintain temperature T 2 heating to a temperature of 100° C., thereby producing a composite article; Includes.

[0022] In step a) of the method, a curable composition is provided comprising a matrix resin and a non-crimped fabric, the non-crimped fabric comprising at least one layer of unidirectionally oriented multifilament carbon yarns and a multifilament suture interconnecting the multifilament carbon yarns, the suture comprising a thermoplastic polymer and having a linear density of 80 dtex or less.

[0023] The term "non-crimped fabric" or "non-crimped fabric", sometimes referred to as "NCF", refers to a structure that includes one or more layers of fibers, filaments, or yarns. The fibers, filaments, or yarns in a single layer are arranged to be parallel to each other and oriented in a single direction (i.e., unidirectional). Multiple layers can be stacked such that the fibers, filaments, or yarns of one layer are oriented parallel to the fibers, filaments, or yarns of an adjacent layer, or oriented crosswise to the fibers, filaments, or yarns of an adjacent layer. When the fibers, filaments, or yarns of one layer are oriented crosswise to the fibers, filaments, or yarns of an adjacent layer, the angle between the axis of one layer (the axis is determined by the fiber, filament, or yarn direction of the layer) and the axis of the adjacent layer can be adjusted virtually infinitely. For example, the angle between adjacent fiber layers can be 0° or 90°, or such angle plus or minus 25°, plus or minus 30°, plus or minus 45°, or plus or minus 60°, with the 0° direction being determined by methods known to those skilled in the art. For example, the machine direction can be designated as the 0° direction. Thus, the term "multiaxial" refers to NCF fabrics having two or more layers with each layer oriented in different directions. Multiaxial fabrics include biaxial fabrics where the layers are oriented in two directions, triaxial fabrics where the layers are oriented in three directions, etc. Multiaxial non-crimped fabrics can be produced, for example, by warp knitting or stitch bonding machines.

[0024] In one embodiment, the non-crimped fabric comprises one layer of unidirectionally oriented multifilament carbon yarns.

[0025] In another embodiment, the non-crimped fabric comprises two or more layers of unidirectionally oriented multifilament carbon yarns.

[0026] In one embodiment, the non-crimped fabric comprises two or more layers of unidirectionally oriented multifilament carbon yarns, the layers being oriented in the same direction, while in another embodiment, the non-crimped fabric comprises two or more layers of unidirectionally oriented multifilament carbon yarns, the layers being oriented in different directions.

[0027] As used herein, a yarn is one or more fibers, one or more filaments, or a continuous strand of material in a form suitable for use in fabric manufacturing, sewing, crocheting, knitting, weaving, sewing, and the like. Yarns include, for example, (1) multiple filaments layered or bundled together without any added or intentional twist (sometimes called zero twist or no twist yarn); (2) multiple filaments layered or bundled together and intertwined, false twisted, or bulked in some way; (3) multiple filaments layered or bundled together with some degree of twist (sometimes called twisted yarn); and (4) a single filament with or without twist (sometimes called monofilament or monofilament yarn). Bulked yarns can be filaments or spun yarns that have been given a significant amount of volume by physical, chemical, or thermal treatment, or a combination thereof. In some cases, the yarns are called filament yarns or multifilament yarns, both of which are generally made from multiple filaments.

[0028] "Fiber" as used herein refers to a material having a high length to thickness ratio. Fibers may be continuous, in which case such fibers are referred to as filaments, or staple lengths (i.e., individual lengths).

[0029] Thus, in one embodiment, the suture comprises one or more thermoplastic fibers or filaments.

[0030] The unidirectionally oriented multifilament carbon yarns within a single layer of the NCF of the present disclosure are interconnected by multifilament sutures having specific properties that contribute to reducing the size of separation zones, such as fisheyes, in the NCF fabric, and thus reducing the size of undesirable resin-rich zones in composite articles made from the NCF fabric.

[0031] The suture comprises a thermoplastic polymer and has a linear density of 80 dtex or less.

[0032] The thermoplastic polymer may be any thermoplastic polymer known to those skilled in the art. Exemplary thermoplastic polymers include, but are not limited to, polycarbonates, polyurethanes, and copolymers thereof. Suitable copolymers include, but are not limited to, copolyesters, copolyamides, copolyimides, copolycarbonates, copolyurethanes, polyesteramides, polyamideimides, polyaramids, polyphthalamides, and poly(ester)carbonates.

[0033] In one embodiment, the thermoplastic polymer comprises a polyamide, a polyester, or a blend or copolymer thereof.

[0034] Examples of suitable polyamides include, but are not limited to, PA6, PA6 / 6, PA6T, PA12, PA6 / 10, PA9T, PA10 / 10, PA10T, PA11, PA6 / 12, PA10 / 12, PA6 / 18, PA6 / 36, PA4 / 6, PA4T, and blends or copolymers thereof.

[0035] In one embodiment, the thermoplastic polymer of the suture is a semi-crystalline polymer.

[0036] The suture is melted at its melting temperature, T m In one embodiment, the suture has a melting temperature of 230° C. or less, typically 220° C. or less. In another embodiment, the suture has a melting temperature of 70° C.-200° C., typically 90° C.-180° C.

[0037] Multifilament sutures can be characterized by certain properties such as linear mass density and / or filament count (if the yarn contains two or more filaments).

[0038] The linear mass density of a yarn is given in units of tex, or more commonly decitex (dtex). 1 tex is defined as the mass in grams per 1000 meters of yarn. Thus, 1 dtex is the mass in grams per 10,000 meters of yarn. According to the invention, the linear density of the multifilament suture is less than or equal to 80 dtex. Typically, the linear density of the multifilament suture is in the range of 1 to 55 dtex, more typically 1 to 40 dtex. In one embodiment, the linear density of the multifilament suture is in the range of 15 to 55 dtex.

[0039] The fibers or filaments of a multifilament suture may be characterized by their density. As used herein, density refers to the density of the polymeric material used to manufacture the fiber. The fibers or filaments of a multifilament suture may have a density between 0.5 and 2.0 g / cm. 3 , typically 0.8 to 1.8 g / cm 3 , more typically 0.9 to 1.5 g / cm 3 In one embodiment, the fibers or filaments of the multifilament suture have a density of 0.9 to 1.4 g / cm 3 has a density of

[0040] As used herein, filament count is the number of filaments that make up the yarn. The filament count of a multifilament suture is no more than 1.0 times the decitex value of the suture, typically no more than 0.9 times the decitex value, and more typically no more than 0.8 times the decitex value.

[0041] In some embodiments, the filament count ranges from 0.1 to 0.8 times the decitex value of the yarn, typically from 0.1 to 0.6 times the decitex value of the yarn, and more typically from 0.1 to 0.5 times the decitex value of the yarn.

[0042] The fibers or filaments of a multifilament suture can be entangled (also called intertwined or intermingled) according to methods known to those skilled in the art. For example, the yarn filaments can be entangled by exposing multiple filaments to a localized fluid jet, such as an air stream. Intertwining creates points of entanglement, called nodes, that are separated by spaces of unentangled filaments.

[0043] Sutures can also be characterized by their twist. As used herein, twist refers to the helical arrangement of fibers or filaments around the axis of the thread. Multifilament sutures of the present disclosure may or may not include twist. Twist, if present, is given as the number of turns per unit length, typically turns per meter. Multifilament sutures usually have a twist of less than 200 turns per meter. In one embodiment, the suture has a twist of less than 150 r / m, typically less than 100 r / m, more typically less than 50 r / m. In one embodiment, the suture has no twist.

[0044] In one embodiment, the non-crimped fabric is multiaxial and comprises two or more layers of unidirectionally oriented multifilament carbon yarns. The layers of the multiaxial NCF fabric can be connected and secured together according to methods known to those skilled in the art, for example, by a plurality of sutures or yarns arranged parallel to each other and running parallel to each other to form a seam. The sutures or yarns used to connect and secure the layers of the multiaxial NCF fabric to each other can be the same or different from the multifilament sutures described herein. In one embodiment, the sutures or yarns used to connect and secure the layers of the multiaxial NCF fabric to each other are the same as the multifilament sutures described herein.

[0045] Multifilament sutures hold unidirectionally oriented multifilament yarns together within a single layer of NCF and / or secure two or more layers of NCF fabric together and do not provide structural reinforcement. Thus, multifilament sutures used in accordance with the present disclosure to interconnect unidirectionally oriented multifilament carbon yarns within a single layer of NCF and / or to unite two or more layers in an NCF fabric are non-structural. In contrast, unidirectionally oriented multifilament carbon yarns are structural because they provide structural reinforcement to a composite material or an article made therefrom.

[0046] The non-crimped fabric may further comprise one or more layers of a veil, typically a nonwoven veil. For example, the non-crimped fabric may comprise a layer of unidirectionally oriented multifilament carbon yarns combined with a layer of veil. Any veil known to those skilled in the art may be used. The layers constituting the NCF fabric, including one or more layers of veil, may be connected and secured to each other according to methods known to those skilled in the art, for example by multiple sutures or knitting threads. When used, the veil layer advantageously improves process performance, such as permeability, and mechanical performance, such as impact resistance and delamination resistance. Exemplary veils that may be used are described in PCT Publication Nos. WO 2017 / 083631 and WO 2016 / 003763, which are incorporated by reference. The veil may be manufactured from materials known to those skilled in the art.

[0047] Non-crimped fabrics can be obtained from commercial sources or can be manufactured according to methods known to those skilled in the art. Unidirectionally oriented multifilament carbon yarns can be interconnected to form a single layer of NCF. Multiple such single layers of NCF can be combined to form a multi-layered NCF fabric with multiple layers interconnected using the sutures described herein.

[0048] The interconnection of unidirectionally oriented multifilament carbon yarns within a single layer of NCF and / or the integration of two or more layers in an NCF fabric can be achieved using a variety of stitch types, stitch widths (i.e., distance between points in the weft direction), and stitch lengths (i.e., distance between points in the weft direction) known to those skilled in the art. Suitable stitch patterns include straight stitches, chain stitches, double stitches, zigzag stitches, tricot stitches, or combinations thereof. In one embodiment, the stitch pattern is a tricot stitch, typically a zigzag tricot stitch. There are no particular limitations on usable stitch widths and stitch lengths. For example, the stitch width may range from 1 to 20 mm, typically from 1 to 10 mm. The stitch length may range from 1 to 20 mm, typically from 1 to 10 mm, for example.

[0049] When the NCF fabric comprises two or more layers, the layers can be connected and secured together by sewing or knitting according to known methods using a suture, such as the multifilament suture described herein. When the NCF fabric is multiaxial, the manufacture of such multiaxial NCF is known and utilizes conventional techniques, for example those described in the book "Textile Structural Composites, Composite Materials Series Volume 3" by Tsu Wei Chou & Franck K. Ko, ISBN-0-44442992-1, Elsevier Science Publishers BV, 1989, Chapter 5, paragraph 3.3.

[0050] The curable composition can be provided by molding a support structure containing the NCFs described herein and injecting or pouring a thermosetting resin into the support structure in a number of liquid molding processes.

[0051] The term "support structure" as used herein refers to a construction in which one or more layers of a reinforcing material, such as the NCF fabric described herein, are placed without a matrix resin into a mold for further processing, such as by injecting or pouring a matrix resin, to form a curable composition, which may then be cured to form a composite article. An example of a support structure is a fiber preform.

[0052] The support structure may further include any type of textile layer known to those skilled in the art for producing composite materials. Examples of suitable fabric types or configurations include, but are not limited to, all woven fabrics (examples of which are plain weave, twill, satin, spiral weave, and mono weave fabrics); warp knitted fabrics; knitted fabrics; braided fabrics; all nonwoven fabrics (examples of which are, but are not limited to, nonwoven veils, mat fabrics composed of chopped and / or continuous fiber filaments, felts, etc.), as well as combinations of the aforementioned fabric types.

[0053] In one embodiment, the support structure may further include a veil, typically a nonwoven veil. Any veil known to those skilled in the art may be used. For example, the veil described in PCT Publication No. WO 2017 / 083631 may be used. The binder component may be distributed on at least one side of the veil layer or through a portion of the veil, or may be distributed throughout the non-crimped fabric, including the spaces between the unidirectionally oriented fibers and the portion of the veil. For example, the binder described in PCT Publication No. WO 2016 / 003763, which is incorporated herein by reference, may be used. The binder may be present in an amount of 15% or less by weight of the final fabric. Typically, the binder component does not form a continuous film on the surface of the fibrous material. The veil may be made from materials known to those skilled in the art. For example, the veil may be made from the same materials as the sutures described herein.

[0054] Liquid molding processes that can be used include, but are not limited to, vacuum-assisted resin transfer molding (VARTM), where a vacuum-induced pressure differential is used to inject resin into a support structure. Another method is resin transfer molding (RTM), where resin is pressure-injected into a support structure in a closed mold. A third method is resin film infusion (RFI), where semi-solid resin is placed under or over a support structure, appropriate tooling is placed on the part, the part is bagged, and then placed in an autoclave to melt and inject the resin into the support structure.

[0055] The matrix resin for impregnating, injecting, or injecting into the support structure described herein comprises a curable resin, and optionally suitable additives known to those skilled in the art. "Curing" or "cure" in this disclosure refers to the solidification of a polymeric material by chemical cross-linking of the polymer chains. The term "curable" with respect to a composition means that the composition can be subjected to conditions that cause the composition to become solidified. In one embodiment, the matrix resin is a thermosetting resin composition comprising one or more uncured thermosetting resins.

[0056] Suitable thermosetting resins include, but are not limited to, epoxy resins, oxetanes, imides (such as polyimides or bismaleimides), vinyl ester resins, cyanate ester resins, isocyanate modified epoxy resins, phenolic resins, furan resins, benzoxazines, formaldehyde condensation resins (such as urea, melamine, or phenolic), polyesters, acrylics, hybrids, blends, and combinations thereof.

[0057] Suitable epoxy resins include glycidyl derivatives of aromatic diamines, aromatic monoprimary amines, aminophenols, polyhydric phenols, polyhydric alcohols, polycarboxylic acids, and non-glycidyl resins produced by peroxidation of olefinic double bonds. Examples of suitable epoxy resins include polyglycidyl ethers of bisphenols such as bisphenol A, bisphenol F, bisphenol S, bisphenol K, and bisphenol Z; polyglycidyl ethers of cresols and phenolic novolacs, glycidyl ethers of phenol-aldehyde adducts, glycidyl ethers of aliphatic dialkyl, diglycidyl ethers, diethylene glycol diglycidyl ethers, aromatic epoxy resins, aliphatic polyglycidyl ethers, epoxidized olefins, brominated resins, aromatic glycidyl amines, heterocyclic glycidyl imides and amides, glycidyl ethers, fluorinated epoxy resins, or combinations thereof.

[0058] Specific examples are the tetraglycidyl derivative of 4,4'-diaminodiphenylmethane (TGDDM), resorcinol diglycidyl ether, triglycidyl-p-aminophenol, triglycidyl-m-aminophenol, bromobisphenol F diglycidyl ether, the tetraglycidyl derivative of diaminodiphenylmethane, trihydroxyphenylmethane triglycidyl ether, polyglycidyl ether of phenol-formaldehyde novolac, polyglycidyl ether of o-cresol novolac or the tetraglycidyl ether of tetraphenylethane.

[0059] Suitable oxetane compounds, which are compounds containing at least one oxetano group per molecule, include, for example, compounds such as 3-ethyl-3[[(3-ethyloxetan-3-yl)methoxy]methyl]oxetane, oxetane-3-methanol, 3,3-bis-(hydroxymethyl)oxetane, 3-butyl-3-methyloxetane, 3-methyl-3-oxetanemethanol, 3,3-dipropyloxetane, and 3-ethyl-3-(hydroxymethyl)oxetane.

[0060] In one embodiment, the matrix resin comprises an epoxy resin.

[0061] The curable matrix resin may optionally contain one or more additives such as curing agents, curing catalysts, comonomers, rheology control agents, tackifiers, inorganic or organic fillers, thermoplastic and / or elastomeric polymers as reinforcing agents, stabilizers, inhibitors, pigments, dyes, flame retardants, reactive diluents, UV absorbers and other additives known to those skilled in the art to improve the properties of the matrix resin before and / or after curing.

[0062] Examples of suitable curing agents include, but are not limited to, aromatic, aliphatic and cycloaliphatic amines or guanidine derivatives. Suitable aromatic amines include 4,4'-diaminodiphenylsulfone (4,4'-DDS), and 3,3'-diaminodiphenylsulfone (3,3'-DDS), 1,3-diaminobenzene, 1,4-diaminobenzene, 4,4'-diammodiphenylmethane, benzenediamine (BDA); suitable aliphatic amines include ethylenediamine (EDA), 4,4'-methylenebis(2,6-diethylaniline) (M-DEA), m-xylylenediamine (mXDA), diethylenetriamine (DETA), triethylenetetramine (TETA), trioxatridecanediamine (TTDA), polyoxypropylenediamine, and further homologues, diamino cycloaliphatic amines such as cyclohexane (DACH), isophorone diamine (IPDA), 4,4' diaminodicyclohexylmethane (PACM), bisaminopropylpiperazine (BAPP), N-aminoethylpiperazine (N-AEP); other suitable curing agents include anhydrides, typically polycarboxylic acid anhydrides, such as nadic anhydride, methylnadic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, pyromellitic dianhydride, chlorendic anhydride, and trimellitic anhydride.

[0063] Still other hardeners are Lewis acid:Lewis base complexes. Suitable Lewis acid:base complexes include, for example, BCl 3 : Amine complex, BF 3 amine complexes, e.g. BF 3 : Monoethylamine, BF 3 : Propylamine, BF 3 : Isopropylamine, BF 3 : Benzylamine, BF 3 : Chlorobenzylamine, BF 3: Trimethylamine, BF 3 : Pyridine, BF 3 :THF, AlCl 3 :THF, AlCl 3 : Acetonitrile, and ZnCl 2 :THF and other complexes.

[0064] Additional curing agents are polyamides, polyamines, amidoamines, polyamidoamines, polycycloaliphatic, polyetheramides, imidazoles, dicyandiamide, substituted ureas and urones, hydrazines and silicones.

[0065] Urea-based hardeners range from materials available under the tradename DYHARD (sold by Alzchem), and urea derivatives such as those sold as UR200, UR300, UR400, UR600, UR700, etc. Uron accelerators include, for example, 4,4-methylenediphenylenebis(N,N-dimethylurea) (available from Onmicure as U52M), etc.

[0066] When present, the total weight of the curing agent is in the range of 1% to 60% by weight of the resin composition. Typically, the curing agent is present in the range of 15% to 50% by weight, more typically in the range of 20% to 30% by weight.

[0067] Suitable toughening agents may include, but are not limited to, homopolymers or copolymers, either alone or in combination, of polyamides, copolyamides, polyimides, aramids, polyketones, polyetherimides (PEI), polyetherketones (PEK), polyetherketoneketones (PEKK), polyetheretherketones (PEEK), polyethersulfones (PES), polyetherethersulfones (PEES), polyesters, polyurethanes, polysulfones, polysulfides, polyphenylene oxides (PPOs) and modified PPOs, poly(ethylene oxide) (PEOs) and polypropylene oxides, polystyrenes, polybutadienes, polyacrylates, polystyrenes, polymethacrylates, polyacrylics, polyphenylsulfones, high performance hydrocarbon polymers, liquid crystal polymers, elastomers, segmented elastomers, and core-shell particles.

[0068] The reinforcing particles or agents, when present, may range from 0.1 wt% to 30 wt% of the resin composition. In one embodiment, the reinforcing particles or agents may be present in the range of 10 wt% to 25 wt%. In another embodiment, the reinforcing particles or agents may be present in the range of 0.1 to 10 wt%. Suitable reinforcing particles or agents include, for example, Virantage VW10200FRP, VW10300FP, and VW10700FRP from Solvay, BASF Ultrason E2020 and Sumikaexcel 5003P from Sumitomo Chemical.

[0069] The reinforcing particles or agents may be in the form of particles having a diameter of 5 microns or less, typically 1 micron or less. The size of the reinforcing particles or agents may be selected so as not to be filtered by the fiber reinforcement. Optionally, the composition may also include silica gel, calcium silicate, silica oxide, phosphates, molybdates, fumed silica, amorphous silica, amorphous fused silica, clays such as bentonite, organoclays, aluminum trihydrate, hollow glass microspheres, hollow polymeric microspheres, microballoons, and calcium carbonate.

[0070] The composition may also include conductive particles such as those described in PCT Publication Nos. WO 2013 / 141916, WO 2015 / 130368 and WO 2016 / 048885.

[0071] The carbon of the multifilament carbon yarn may be in the form of graphite. The carbon may be metallized with a discontinuous or continuous metal layer. Graphite fibers that have been found to be particularly useful in the present invention are those supplied by Solvay under the trade names T650-35, T650-42, and T300; those supplied by Toray under the trade names T700, T800, and T1000; and those supplied by Hexcel under the trade names AS4, AS7, IM7, IM8, and IM10. The carbon fibers, typically filaments, may be unsized or sized with a material compatible with the resin composition.

[0072] Molds for resin infusion may be two-component sealed or single-sided with a vacuum bag.

[0073] The curable composition can be prepared according to any suitable method known to those skilled in the art. One suitable method for preparing the curable composition includes providing a support structure in a mold and then injecting or injecting one or more layers of non-crimped fabric with a matrix resin as described herein. Typically, the support structure and / or matrix resin are at a certain temperature during the injection or injection process. In this specification, "injection" or "injection" refers to the combination of the support structure and the matrix resin, and these terms can be used interchangeably. However, for simplicity, "injection temperature" is used to refer to the temperature at which the support structure and the matrix resin are combined. Thus, the curable composition can be provided at a certain injection temperature, which is typically higher than ambient temperature, i.e., higher than 25°C.

[0074] In step b) of the method, the curable composition is heated to a temperature T 1It is heated to T 1 is the melting temperature of the suture (T m ) and T m Or T 1 The conversion of the curable composition at is 30% or less, typically 20% or less, more typically 10% or less.

[0075] The conversion of the curable composition refers to the percentage of resin that has been converted to polymer. The conversion is determined by differential scanning calorimetry (DSC) using known equipment and methods on a sample of the curable composition. The sample of the curable composition can be subjected to a desired heating profile using DSC, and the conversion of the curable composition can be determined at selected points along the heating profile. According to the method of the present invention, T m Or T 1 The conversion of the curable composition at should be 30% or less, typically 20% or less, more typically 10% or less.

[0076] Advantageously, the curable composition is applied to the T of the suture. m A temperature higher than T 1 While heating to T m Or T 1 It has been discovered that conversion of the curable composition at or below 30% in the curing step allows for the production of composite parts that exhibit significant resistance to the formation of microcracks. Without wishing to be bound by theory, it is believed that at or below 30% conversion, the matrix resin is not viscous or stiff enough to retain the shape of the sutures. Thus, upon melting, the sutures are able to interdiffuse with the matrix resin (as described below). A manifestation of this effect is a significant reduction in microcracking in the final composite article.

[0077] Typically, the composition is heated to a temperature T 1 Heating to a temperature T can be accomplished by any method known to one of ordinary skill in the art. In one embodiment, the curable composition is heated to a temperature T 1 Heating the curable composition to a temperature T1 Heating to a temperature of 0.2 to 10° C. / min includes heating the curable composition at a heating rate of 0.2 to 10° C. / min, typically 0.5 to 2° C. / min.

[0078] The melting temperature of the suture, T m Any temperature T higher than 1 However, in one embodiment, the temperature T 1 is the cure temperature of the curable composition. The cure temperature of the curable composition refers to the temperature required for the composition to cure, and typically depends on the resin system used in the curable composition. In some cases, the curable composition may be delivered at a specific injection temperature, typically higher than ambient temperature, i.e., higher than 25° C. Thus, in some embodiments, the curable composition is delivered at an injection temperature, T 1 is the injection temperature and the T of the suture m Higher than both.

[0079] In step c) of the method, the curable composition is cured at a temperature T 1 is maintained or the temperature T 2 Heating is then performed until a composite article is produced.

[0080] During the curing process, the matrix resin forms crosslinks throughout the curable composition and the resin is said to be a gel. Upon gelation, the matrix resin no longer flows but rather behaves as a solid. The temperature at which gelation occurs is called the gelation temperature T gel The T of a particular composition gel is typically determined by performing dynamic rheological measurements on a sample of the curable composition using known methods. Typically, a temperature sweep is applied at different frequencies (1, 3, 5, and 10 Hz) up to 300°C. At a certain temperature, the tan δ (=G″ / G′) curves at different frequencies intersect, which is interpreted as the gel temperature of the polymer sample. In some embodiments, the T of the suture m is the T of the curable composition gel Lower than.

[0081] Further heating reaches temperature T2 If the 2 As long as the curing process is not compromised, T 1 The temperature may be any suitable temperature greater than .

[0082] Any time sufficient for the curable composition to cure is suitable for carrying out the process.However, in one embodiment, the time sufficient for the curable composition to cure is 6 hours or less, typically 5 hours or less.In some embodiments, the time sufficient for the curable composition to cure is 3 hours or less, typically 2 hours or less.

[0083] Surprisingly, composite articles made according to the processes described herein exhibit reduced microcracking when compared to composite articles made using the same process with a suture yarn that does not contain a thermoplastic polymer and has a linear density of 80 dtex or less, and even when compared to composite articles made using a different process with a suture yarn that contains a thermoplastic polymer and has a linear density of 80 dtex or less. Without wishing to be bound by theory, it is believed that the curable composition is applied to the suture yarn while controlling the conversion of the curable composition to 30% or less. m A temperature higher than T 1 It is believed that heating to a temperature of 100° C. results in a unique interaction between the matrix resin and the suture, referred to herein as interdiffusion. It is believed that the suture and matrix resin in the non-crimped fabric interdiffuse during the process, resulting in little or no regions having only the chemical characteristics of the suture. In other words, the suture diffuses toward the matrix resin as it melts, while the matrix resin, which has not yet gelled and is not yet viscous or stiff enough to take the shape of the suture, also diffuses toward the suture. Thus, interdiffusion of the two materials occurs within the hardenable composition, resulting in desirable bulk properties, such as reduced microcracking.

[0084] Composite articles manufactured according to the methods described herein can be evaluated for microcracking using methods known to those skilled in the art. Typically, a baseline evaluation of microcracking in the composite article is performed since microcracking is known to occur as a result of the manufacturing process. To evaluate microcracking due to exposure to thermal cycling and high humidity periods, a sample of the composite article can be subjected to conditions in which it is maintained at an ambient temperature and / or humidity level for a specified time, and then adjusted to another temperature and / or humidity level at a specified rate, and then maintained for a specified time. This process, typically known as moist heat loading or cycling, can be repeated at the user's request to simulate real-world conditions in which the composite article may be used. When exposed to moist heat loading conditions, microcracking may be observed in the composite article. Quantification of microcracking is typically performed using optical microscopy at the scale of each ply and fiber.

[0085] The processes including the NCF fabrics, sutures, support structures, and curable compositions used therein, and the composite articles produced, are further illustrated by the following non-limiting examples. EXAMPLES

[0086] Example 1. Preparation of NCF composite material Unless otherwise indicated, the non-crimped fabrics (NCF) used herein were manufactured and supplied by CHOMARAT (France). Carbon fiber (Toho Tenax IMS65 24k E23) was used to manufacture the NCF on a Karl Mayer MAX 5 multiaxial machine. The NCF was a bi-oriented NCF with two carbon fiber layers superimposed (the first top layer oriented at +45° and the second bottom layer at -45°). The construction was Biax and the NCF width was 125 cm. The two layers were sewn with various suture threads. The stitch pattern was a zigzag tricot stitch pattern, specifically Tricot E5 with a stitch length of 3.3 mm. The surface mass per ply was 196±5 g / m 2 It is.

[0087] The biaxial NCF layups were impregnated with resin (EP2400PRISM™, available from Solvay) using a vacuum assisted resin infusion process and cured according to the supplier's instructions. The resin was first heated to 100° C. in a vacuum oven and then vacuum degassed for 15 minutes. Infusion was performed at 100° C. under a vacuum of approximately 10 mbar.

[0088] Two different curing profiles were used to cure the NCF composites. In one curing profile, Profile A, the plate was heated to 180°C at 2°C / min, held at 180°C for 2 hours, and then cooled to 80°C at 0.5°C / min. In another curing profile, Profile B, the plate was heated to 110°C at 2°C / min, held at 110°C for 12 hours, then heated again to 180°C at 2°C / min, held at 180°C for 2 hours, and then cooled to 80°C at 0.5°C / min. In Profile A, the conversion of the NCF composite at 180°C was about 6%. In Profile B, the conversion of the NCF composite by the time it was heated to 180°C was about 50%. The NCF composites produced are summarized in Table 1 below.

[0089] [Table 1]

[0090] Example 2. Hygrothermal loading of NCF composite material NCF composites produced according to Example 1 were subjected to 2000 accelerated hygrothermal loads representing typical operating conditions during the life cycle of a subsonic jet (see Figure 1). The load had five blocks of 400 cycles, each block consisting of two different loading stages: a first steady stage "water absorption" in which the sample was exposed to 95% RH at 50°C for 12 hours, and a second thermal drying cycle stage. During this last stage, the sample was cycled 400 times at a temperature rate of 9°C / min in the temperature range from -54 to 80°C. Each cycle lasted for 1 hour (4 x 15 min), which theoretically gives a duration of 15 minutes for each ramp up / down and 15 minutes for each isothermal step at 80°C and -54°C. In total, it took about 3 months to reach 2000 cycles. The minimum dimensions of the cycled samples were 50 x 50 mm. 2 It is.

[0091] Example 3. Quantification of Microcracks Samples of NCF composites subjected to the heat and humidity loading procedure described in Example 2 (i.e., cycled samples) were taken after every 400 cycles, i.e., 400, 800, 1200, 1600, and 2000 cycles. After every 400 heat and humidity cycles (12 hours of conditioning in wet conditions followed by 400 heat cycles), 20 x 20 x 3.2 mm 3 The microcrack analysis samples with a size of 20 × 3.2 mm were taken from the center of the samples after cycling. These analysis samples were carefully cut with a microslitter to avoid damage caused by cutting. 2 ) were polished with an automatic polishing machine (Struers TegraPol). For each material, a microcrack analysis step (e.g. 400 cycles) needs to be prepared with a single cycled specimen (one cut and three polishing steps). Thus, for a complete analysis of 2000 cycles (5 × 400 hygrothermal cycles), five specimens are required per material type (one sample per analysis step). The total microcrack density (density, cm) of each composite analyzed was -1 ) are summarized in Table 2 below.

[0092] [Table 2]

[0093] Example 4. Characterization of NCF composite materials The cured NCF composites were examined by infrared spectroscopy. The chemical composition of the polymer suture / cured epoxy resin region was determined using infrared ATR germanium technique in reflectance mode. Samples of 20 × 20 mm were cut and then coated with Struers Caldo Fix epoxy resin polished with 0.3 μm particles. The instrument used for infrared analysis was a Bruker Vertex70 and the instrument used for microscopy was a Hyperion2000.

[0094] Compositional profiles (mapping) were determined along defined paths every 10-30 μm within the area of ​​the sample. Samples 3 and 5 were analyzed. The IR bands of interest were the band corresponding to the polyamide of the suture, i.e. 1637 cm -1 C=O band (band 1, C=O stretching), 1550 cm -1 NH (band 2, NH deformation and CN stretching), and harmonics of band 2 at 1550 cm-1, 3082 and 3086 cm -1 For epoxy resin, the -1 The symmetric bond vibrations of CO and CC in the epoxy cycle were targeted.

[0095] It was observed that in Sample 5, melting of the suture did not appear to cause loss of shape of the suture filament. In the region of the suture filament, the infrared spectrum shows vibrational bands attributed to polyamide, suggesting that the chemical composition of this region is that of the suture. In the epoxy region, the infrared spectrum shows vibrational bands attributed to the epoxy resin, suggesting that the chemical composition of this region is that of the matrix resin.

[0096] However, in sample 3, the shape of the suture filament appears to have disappeared due to melting of the suture. The infrared spectrum of any selected region, whether the suture filament region or the epoxy region, showed both vibration bands due to polyamide and vibration bands due to epoxy resin, suggesting that the chemical composition of the selected region was due to a mixture of both the cured epoxy resin and the suture polymer.

Claims

1. 1. A method for making a composite article, comprising the steps of: a) providing a curable composition comprising a matrix resin and a non-crimped fabric, the non-crimped fabric comprising at least one layer of unidirectionally oriented multifilament carbon yarns and a multifilament suture interconnecting the multifilament carbon yarns, the suture comprising a thermoplastic polymer and having a linear density of 80 dtex or less; b) The curable composition is heated to a temperature T １ Heating to T １ is the melting temperature of the suture (T ｍ ) and T ｍ Or T １ the conversion of the matrix resin in is 30% or less, typically 20% or less, more typically 10% or less; c) at a temperature T for a time sufficient to cure the curable composition. １ or maintain temperature T ２ heating to a temperature of 100° C., thereby producing a composite article; The method includes:

2. 10. The method of claim 1, wherein the time sufficient for the curable composition to cure is 6 hours or less, typically 5 hours or less.

3. 3. The method of claim 1 or 2, wherein the suture has a melting temperature of 230°C or less, typically 220°C or less.

4. The method of claim 1 or 2, wherein the melting temperature of the suture is between 70°C and 200°C, typically between 90°C and 180°C.

5. The method of claim 1 or 2, wherein the suture comprises one or more thermoplastic fibers or filaments.

6. 3. The method of claim 1 or 2, wherein the thermoplastic polymer of the suture is a polymer selected from the group consisting of polyesters, polyamides, polyimides, polycarbonates, polyurethanes, and copolymers thereof, such as copolyesters, copolyamides, copolyimides, copolycarbonates, copolyurethanes, polyesteramides, polyamideimides, polyaramids, polyphthalamides, and poly(ester)carbonates.

7. 3. The method of claim 1 or 2, wherein the linear density of the multifilament suture is in the range of 1 to 55 dtex, more typically 1 to 40 dtex.

8. 3. The method of claim 1 or 2, wherein the non-crimped fabric is multiaxial and comprises two or more layers of unidirectionally oriented multifilament carbon yarns.

9. The method of claim 1 or 2, wherein the non-crimped fabric further comprises a veil, typically a nonwoven veil.

10. The curable composition is heated to the temperature T. １ 3. The method of claim 1 or 2, wherein heating to comprises heating the curable composition at a heating rate of about 10° C. / min or less.

11. The curable composition is heated to the temperature T. １ 3. The method of claim 1 or 2, wherein heating to a temperature of 0.2 to 10° C. / min comprises heating the curable composition at a heating rate of 0.2 to 10° C. / min, typically 0.5 to 2° C. / min.

12. The temperature T １ The method of claim 1 or 2, wherein:

13. The T of the suture ｍ is the temperature at which the curable composition gels (T ｇｅｌ 3. The method of claim 1 or 2, wherein the concentration of

14. The curable composition is provided at an injection temperature, T １ is the injection temperature and the T ｍ The method of claim 1 or 2, wherein the temperature is higher than both of the above.

15. The method of claim 1 or 2, wherein the thermoplastic polymer of the suture is a semi-crystalline polymer.

16. The method of claim 1 or 2, wherein the matrix resin comprises an epoxy resin.

17. 3. The method of claim 1 or 2, wherein the sutures and the matrix resin of the non-crimped fabric interdiffuse during the process so that there are few or no regions having only the chemistry of the sutures.

18. 3. The method of claim 1 or 2, wherein the composite article produced exhibits reduced microcracking compared to a composite article produced using a suture that does not include a thermoplastic polymer and has a linear density of 80 dtex or less.

19. A composite article produced according to the method of claim 1 or 2.

20. a) providing a curable composition comprising a matrix resin and a non-crimped fabric, the non-crimped fabric comprising at least one layer of unidirectionally oriented multifilament carbon yarns and a multifilament suture interconnecting the multifilament carbon yarns, the suture comprising a thermoplastic polymer and having a linear density of 80 dtex or less; b) The curable composition is heated to a temperature T １ Heating to T １ is the melting temperature of the suture (T ｍ ) is higher than the T ｍ Or T １ the conversion of the matrix resin in is 30% or less, typically 20% or less, more typically 10% or less; c) at a temperature T for a time sufficient to cure the curable composition. １ or maintain temperature T ２ Heating until 23. A composite article manufactured by a method comprising:

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