How to Insert a Shim into an Assembly

Abstract

A method for manufacturing a structural shim (220) for a bonded assembly of components, such as one installed between an aircraft skin (212) and a substructure (214), includes disposing a hardenable composition (216) in a gap between a first component (212) and a second component (214), hardening the hardenable composition to provide a dimensionally stable shim pattern (218), and removing the shim pattern from the gap without damage. The shim pattern can be used to provide a digital model thereof, which can be used to manufacture the structural shim (220).

Description

Technical Field

[0001] A method for manufacturing and using a shim for filling a gap between joint portions of component surfaces is provided. Such component surfaces can be, for example, the surfaces of aircraft components.

Background Art

[0002] A shim is a thin piece of material used to fill small gaps or spaces between components joined to each other. The shim assumes the shape of the gap and can support a compressive load when fixed to each other to prevent excessive distortion and damage to structural components. Shims are used in industrial applications such as automotive and aerospace manufacturing, as well as residential and commercial construction.

[0003] In the aerospace field, the dimensional accuracy of shims is particularly important for ensuring proper assembly of components and the structural integrity of aircraft. To attach an aerodynamic surface or skin to an internal infrastructure, it is necessary to attach the components to each other at the joint surface without leaving a gap larger than a predetermined tolerance. To provide the desired aerodynamic performance and structural integrity, gaps larger than the predetermined tolerance must be filled with shims.

[0004] Various types of shims can be used. A solid shim may be made of the same material as the joint. A laminated peelable shim can be manufactured with multiple foil layers that can be removed one by one until a preferred fit is achieved. Liquid shim materials function well to fill irregular or tapered joint surfaces and are typically used to fill gaps less than 0.7 millimeters wide.

[0005] Determining the requirements, size, and shape of a given shim can be an iterative and labor-intensive process. Generally, parts are temporarily assembled, then visually inspected and measured for gaps between the outer skin and the underlying structure. The parts may then be disassembled and test shims will be produced. The parts can then be reassembled with the test shims temporarily in place to confirm the fit. This is a second temporary assembly operation and such operations may need to be repeated until an appropriate fit is achieved. SUMMARY OF THE INVENTION

[0006] There is a need for methods and related apparatus for creating physical and / or computerized models of gaps so that appropriate shims can be produced without the need for expensive and time-consuming iterative processes that affect the manufacturing flow.

[0007] The present disclosure provides compositions and methods for creating a physical model of a gap. The physical model provides information that can then be used to produce a shim having an appropriate size and shape. The invention also includes the manufacture of shims and the installation of shims within gaps in aircraft structures.

[0008] In a first aspect, a method of manufacturing a structural shim to be installed between a first part and a second part of an assembly is provided. The method includes placing a hardenable composition within the gap between the first part and the second part, hardening the hardenable composition to provide a dimensionally stable shim pattern, removing the shim pattern from the gap, where the shim pattern can be removed from the gap without damage, creating a digital model of the shim pattern, and using the digital model to manufacture the structural shim.

[0009] In a second aspect, a method of joining an outer skin and an underlying structure of an aircraft is provided, the method including manufacturing a structural shim according to the method described above, inserting the structural shim between the outer skin and the underlying structure, and securing the outer skin and the underlying structure to one another.

[0010] In a third aspect, a method of manufacturing a shim pattern for manufacturing a structural shim installed between the outer skin and the basic structure of an aircraft is provided, the method comprising disposing a hardenable composition within the gap between the outer skin and the basic structure and hardening the hardenable composition to provide a shim pattern, the shim pattern being dimensionally stable, hardening, and removing the shim pattern from the gap, the removing being capable of removing the shim pattern from the gap without damage.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

[0012] When reference characters are repeatedly used in the specification and drawings, they are intended to represent the same or similar functional parts or elements of the present disclosure. Those skilled in the art should understand that many other modifications and embodiments can be devised, which are included within the scope and spirit of the principles of the present disclosure. The figures may not be drawn to scale.

[0013] Definitions “Alkoxy” refers to an oxygen atom bonded to an alkyl group and includes a cycloalkyl group.

[0014] “Alkyl” refers to linear and branched alkyl groups, as well as cycloalkyl groups having from 1 to 40 carbon atoms, from 1 to about 20 carbon atoms, from 1 to 12 carbon atoms, or in some embodiments from 1 to 8 carbon atoms.

[0015] “Ambient temperature” means 25 degrees Celsius.

[0016] As used herein, "aryl" refers to a cyclic aromatic hydrocarbon group that does not contain a heteroatom in the ring.

[0017] "Curing" means forming a chemically cross-linked polymer network.

[0018] "Cycloalkyl" refers to a cyclic alkyl group such as, but not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups.

[0019] "Organic group" refers to any carbon-containing functional group.

[0020] "Substantially" means mostly or almost, or 100%, such as in cases of at least about 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more.

[0021] "Substituted", in connection with a molecule or organic group as defined herein, refers to a state in which one or more hydrogen atoms contained therein are replaced by one or more non-hydrogen atoms.

DETAILED DESCRIPTION OF THE INVENTION

[0022] As used herein, the terms "preferred" and "preferably" refer to the embodiments described herein that can provide certain advantages under certain circumstances. However, other embodiments may also be preferred in the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are not useful, nor is it intended to exclude other embodiments from the scope of the invention.

[0023] As used in this specification and the appended claims, unless the context clearly dictates otherwise, the singular forms "a", "an", and "the" include plural referents. Thus, for example, references to a component preceded by "a" or "the" may include one or more of the component and its equivalents known to those skilled in the art. Further, the term "and / or" means any one or all of the listed elements, or any combination of any two or more of the listed elements.

[0024] In the methods described herein, steps can be performed in any order, without departing from the principles of the disclosure, unless a temporal or operational order is explicitly recited. Further, unless the claims explicitly recite that certain acts are to be performed separately, those acts can be performed simultaneously. For example, the claimed act of doing X and the claimed act of doing Y can be performed simultaneously in a single operation, and the resulting process falls within the literal scope of the claimed process.

[0025] Note that the terms "comprising" and variations thereof do not have a limiting meaning when these terms appear in the appended description. Still further, "a", "an", "the", "at least one", and "one or more" are used interchangeably herein. Relative terms such as left, right, front, rear, top, bottom, side, above, below, horizontal, and vertical may be used herein, and in that case, are from the perspective seen in that particular figure. However, these terms are used merely to simplify the description and are in no way intended to limit the scope of the invention.

[0026] Throughout this specification, references to "one embodiment", "certain embodiments", "one or more embodiments", or "an embodiment" mean that the particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, appearances of the phrases "in one or more embodiments", "in certain embodiments", "in one embodiment", or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment of the invention.

[0027] In this specification, a structural shim for component assembly is provided. The assembled components may in some cases be used in automotive, aerospace, marine, residential, construction, or other commercial or industrial applications.

[0028] In some embodiments, the components with shims are aircraft components. Examples of aircraft components include aircraft outer panels and the underlying structure. The underlying structure of the aircraft is not particularly limited and can include, for example, stringers, ribs, spars, and other framework elements of the aircraft wings and fuselage.

[0029] The structural shim is a fly-away component of the aircraft and is manufactured from a rigid load-bearing material. These shims are used to fill the gaps between assembled components that would otherwise cause dents or buckling of the components and the accompanying stress concentrations. These stress concentrations, if severe, can damage the fixtures and ultimately cause significant damage to the aircraft. Therefore, it is desirable to manufacture customized shims that fit precisely into the gaps to be installed.

[0030] Method of manufacturing and assembling the shim An exemplary method of using a customized structural shim is shown in the assembly process depicted in the block diagram of FIG. 1, indicated by numeral 100 in this specification.

[0031] In FIG. 1, block 102 represents an initial step of providing two parts that are assembled together. These parts are generally mating parts having opposing surfaces separated from each other by one or more gaps. The structural shims provided have precise sizes and shapes such that the shim fills the gap exactly while maintaining the separation and relative orientation of the opposing surfaces.

[0032] The gap has a specific three-dimensional shape defined by the position and orientation of the opposing surfaces. The gap dimension therebetween along the opposing surfaces need not be limited. It is very common for the gap to have a varying thickness (defined as the distance between the opposing part surfaces) along the opposing surfaces.

[0033] In some embodiments, the gap is zero or essentially zero along at least a portion of the joint surface (i.e., the parts contact each other at these locations). Otherwise, the gap may have a maximum width of from 500 micrometers to 6350 micrometers, from 500 micrometers to 4750 micrometers, from 500 micrometers to 3175 micrometers, or in some embodiments, less than 500 micrometers, 600, 700, 800, 900, 1000, 1100, 1200, 1500, 1700, 2000, 2200, 2500, 2700, 3000, 3175, 3500, 3750, 4000, 4250, 4500, 4750, 5000, 5500, 6000, 6150, 6350, or 6500 micrometers, equal to this, or greater than this, which is measured along a direction perpendicular to one or both of the opposing part surfaces.

[0034] In block 106, the non-cured pattern composition is disposed within the gap between opposing component surfaces. The non-cured pattern composition is, in some embodiments, a curable composition that can be molded in an uncured state and then cured to form a hardened pattern composition. Alternatively, the non-cured pattern composition may be a molten composition that hardens when disposed within the gap at an elevated temperature and cooled.

[0035] Optionally, as shown in intervening block 104, the non-cured pattern composition is a mixture of two or more components that can react with each other to form a hardened composition.

[0036] In block 108, the non-cured pattern composition is hardened to provide a shim pattern. The shim pattern is preferably dimensionally stable. That is, it is not permanent for it to flow, expand, contract, or change shape as a result of gravity or normal storage and handling.

[0037] Hardening can be performed using any known method. Known methods include hardening by cooling the non-cured pattern composition, or curing of the non-cured pattern composition by a chemical reaction at ambient temperature, heating to a curing temperature above ambient temperature, exposure to actinic radiation, or exposure to moisture.

[0038] The temperature at which hardening occurs generally correlates with the curing agent used in the non-cured composition and may be from -6°C to 350°C, from 0°C to 250°C, from 25°C to 100°C, or in some embodiments, less than, equal to, or greater than -10°C, -6, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 125, 150, 175, 200, 250, 300, or 350°C.

[0039] Also, combinations of the curing mechanisms are possible. For example, a “dual cure” composition undergoes a certain degree of curing immediately upon exposure to ultraviolet (UV) light, while a chemical curing process proceeds simultaneously over a longer time frame. Examples of dual cure compositions and their use are described outside of this specification, for example, in U.S. Patent Application Publication No. 20170362434 (Ye et al.), U.S. Patent Application Publication No. 20190144610 (Moser et al.), and International Patent Application No. 2018227149 (Liu et al.).

[0040] In block 112, the shim pattern, which is hardened at this point, is removed from the gap. Optionally, as shown in block 110, the removal of the shim pattern can be facilitated by moving the two parts away from each other. Alternatively, the shim pattern can have sufficient flexibility to allow its removal without separating the two parts or otherwise moving them relative to each other. In either case, it is preferred that the shim pattern be removed from the gap without damaging either the part surface or the shim pattern itself.

[0041] Preferably, the shim pattern is non - adhesive and cleanly separates from the part surfaces defining the gap. To achieve a clean removal, the residual contamination present on the bonding surfaces should be essentially zero. It is advantageous to minimize or eliminate residues because trace amounts of silicone compounds or other release agents or contaminants can potentially have an adverse effect on subsequent adhesion to the part surface.

[0042] In block 114, next, a structural shim is fabricated based on the dimensions of the shim pattern removed from the gap. The structural shim can be manufactured using any of a variety of known manual and computer - assisted manufacturing methods.

[0043] In a manual manufacturing method, for example, a mold having a negative of the shim pattern can be formed in a heat - resistant material, and then molten metal can be introduced into the mold to cast the structural shim.

[0044] Digital manufacturing methods are also possible. In one method, a three-dimensional (3D) digital model of the shim pattern is manufactured by scanning the shim pattern with a suitable scanner. Useful scanners can capture the size and shape of the shim pattern using X-rays, lasers, computed tomography (CT), and magnetic resonance imaging. Alternatively, this information can be obtained using a contact probe that traces along the surface of the shim pattern. Any of these methods can generate a digital data file representing the dimensions of the shim pattern.

[0045] Optionally, the raw digital model may be digitally cleaned by removing any data points that are considered to be incorrect or unnecessary. For example, data representing portions of the shim pattern that are extruded beyond the gap region can be excluded if necessary. In addition, missing data points can be estimated and added to the software to create a smooth, contoured surface based on the surrounding data points. To create a 3D surface, the digital data may be converted from a digital point cloud to a triangular mesh surface by software from a provider such as Geomagic, Inc. (Triangle Park, NC).

[0046] Using the digital model of the obtained shim pattern, a structural shim can be created using additive manufacturing technology or subtractive manufacturing technology. Examples of additive manufacturing methods include, but are not limited to, 3D printing, selective area laser deposition, or selective laser sintering (SLS), electrophoretic deposition, robocasting, fused deposition modeling (FDM), laminated object manufacturing (LOM), stereolithography (SLA), and photostereolithography. Subtractive manufacturing methods include the use of a computer numerical control (CNC) milling machine to fabricate the structural shim. Preferably, the structural shim is manufactured from a rigid material that does not deform significantly in response to the compressive loads the shim experiences during and after installation.

[0047] In block 116, the structural shim is installed within the gap, and then in block 118, the two components are joined together to verify that the shim properly fills the gap. Preferably, any gap remaining along the mating surface should be less than 500 micrometers, less than 250 micrometers, less than 100 micrometers, or in some embodiments, less than 5 micrometers, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, or 500 micrometers, equal to, or greater than this.

[0048] Finally, block 120 represents the step of completing the assembly by securing the mating components to each other with the structural shim disposed therebetween. In aircraft manufacturing, this can be accomplished using one or more mechanical fasteners.

[0049] Figure 2 shows a series of steps by process 100 applied to an aircraft assembly. In this application, the first component is the aircraft skin 212 and the second component is the aircraft's basic structure 214.

[0050] In step 202, the skin 212 is shown positioned next to the basic structure 214. Here, the basic structure 214 is an aircraft stringer having a generally "L" shaped cross-section. As shown in step 204, a curable composition 216 is placed between the skin 212 and the basic structure 214 such that the two structures described later are in a bonding relationship. The curable composition 216 is then cured and then removed as shown in step 206 to produce a hardened shim pattern 218.

[0051] A computer is then employed to scan the shim pattern 218 to provide a 3D digital model, which is then used to mill a structural shim 220 as provided in step 208. To provide high strength, the structural shim 220 can be manufactured from a metal, typically steel or aluminum. Finally, in step 210, the skin 212, the structural shim 220, and the basic structure 214 are fixed to each other by a rivet 222 passing through all three components. It should be understood that other fixtures or fixing mechanisms may also be used.

[0052] Although not shown in FIGS. 1 - 2, in certain applications, it is possible to use the shim pattern 218 itself as the structural shim. This may not be practical for some parts of the curable / hardened pattern compositions described herein, but it may be possible if the shim pattern is made from a material having sufficient strength and non-compressibility. In this alternative workflow, the process is significantly simplified as no additional steps are required to fabricate the structural shim.

[0053] Shim pattern composition The shim pattern can be manufactured from any of several suitable curable pattern compositions. Curable pattern compositions include compositions that are a fluid liquid or malleable solid at ambient temperature. This allows the compositions to be shaped at the time they are placed within the gaps. If desired, the curable pattern compositions can be extrudable so that they can be dispensed through a nozzle. Dispensers are well known in the art and include, for example, positive displacement pumps and syringes. When cured, these compositions become dimensionally stable.

[0054] Dimensionally stable compositions have a generally fixed size and shape at a given temperature such as ambient temperature. It should be noted that dimensionally stable compositions may have rigidity but this is not essential. For example, the shim pattern can be a cured rubber that can stretch or bend but returns to its original shape upon relaxation.

[0055] In some embodiments, the curable pattern compositions are dimensionally stable at ambient temperature and thus need to be heated during use. For example, the curable pattern compositions can be provided in the form of a solid polymer film or sheet and then heated when placed between or prior to placement between mating surfaces of components. The composition can then be cured by cooling it back down to ambient temperature to obtain the shim pattern.

[0056] In preferred embodiments, the curable pattern compositions cure by a chemical reaction. These include thermosetting compositions, radiation curable compositions, chemically curable compositions, or combinations thereof. The term "thermosetting" refers to a composition that can be cured by applying heat to the composition. The term "radiation curable" refers to a composition that can be cured when exposed to electromagnetic radiation. The term "chemically curable" refers to a composition that can be cured when contacted with a catalyst.

[0057] The shim pattern compositions useful in the provided assembly methods are non-adhesive when hardened. This property allows the newly formed shim pattern to be cleanly removed from the mating surfaces of adjacent parts. Curable compositions particularly useful for this purpose include polythiols such as polythioethers or polysulfides. Polythioethers contain thioether bonds (i.e., -S-) in their main chain structure. Polysulfides contain disulfide bonds (i.e., -S-S-) in their main chain structure.

[0058] In some embodiments, the curable composition can be a two-component composition that can be cured by mixing a first component and a second component with each other. For example, the first component can include a polythiol, and the second component can include an oxidizing agent, an unsaturated compound having at least two non-aromatic carbon-carbon double bonds, at least one carbon-carbon triple bond, or a combination thereof. Either the first component or the second component can further include an organoborane-amine complex, an organic or inorganic peroxide, a photoinitiator system, or some combination thereof.

[0059] Useful polythiols are organic compounds having at least two (e.g., at least two, at least three, at least four, or even at least six) thiol groups. To achieve chemical cross-linking between polymer chains in the curable composition, at least one of the polythiols in the first component and / or at least one of the unsaturated compounds in the second component can have an average functionality of at least two.

[0060] The polythiol can be an alkylene, arylene, alkylarylene, arylalkylene, or alkylenearylalkylene having at least two mercaptan groups, and any of the alkylene, alkylarylene, arylalkylene, or alkylenearylalkylene can optionally have one or more oxa (i.e., O), thia (i.e., S), or imino (i.e., NR 3 [wherein R 3is a hydrocarbyl group or H]) group intervenes, and is optionally substituted with alkoxy or hydroxyl.

[0061] Useful dithiols include 1,2-ethanedithiol, 1,2-propanedithiol, 1,3-propanedithiol, 1,3-butanedithiol, 1,4-butanedithiol, 2,3-butanedithiol, 1,3-pentanedithiol, 1,5-pentanedithiol, 1,6-hexanedithiol, 1,3-dimercapto-3-methylbutane, dipentene dimercaptan, ethylcyclohexyldithiol (ECHDT), dimercapto diethyl sulfide, methyl-substituted dimercapto diethyl sulfide, dimethyl-substituted dimercapto diethyl sulfide, dimercapto dioxaoctane, 1,5-dimercapto-3-oxapentane, benzene-1,2-dithiol, benzene-1,3-dithiol, benzene-1,4-dithiol, and tolylene-2,4-dithiol. Examples of polythiols having more than two mercaptan groups include propane-1,2,3-trithiol, 1,2-bis[(2-mercaptoethyl)thio]-3-mercaptopropane, tetrakis(7-mercapto-2,5-dithiaheptyl)methane, and trithiocyanuric acid.

[0062] Polythiols formed by the esterification of polyols with thiol-containing carboxylic acids or their derivatives are also useful. Examples of polythiols formed by the esterification of polyols with thiol-containing carboxylic acids or their derivatives include those prepared by subjecting thioglycolic acid or 3-mercaptopropionic acid to an esterification reaction with several polyols to form mercaptoacetate or mercaptopropionate, respectively.

[0063] Suitable polythiols also include THIOCURE PETMP (pentaerythritol tetra(3-mercaptopropionate)), TMPMP (trimethylolpropane tri(3-mercaptopropionate)), ETTMP (ethoxylated trimethylolpropane tri(3-mercaptopropionate), e.g., ETTMP 1300 and ETTMP 700), GDMP glycol di(3-mercaptopropionate), TMPMA (trimethylolpropane tri(mercaptoacetate)), TEMPIC (tris[2-(3-mercaptopropionyloxy)ethyl]isocyanurate), and PPGMP (propylene glycol 3-mercaptopropionate), as commercially available from Bruno Bock Chemische Fabrik GmbH & Co. KG. Specific examples of polymeric polythiols are polypropylene-ether glycol bis(β-mercaptopropionate), prepared by esterification from polypropylene-ether glycol (e.g., PLURACOL P201, Wyandotte Chemical Corp.) and β-mercaptopropionic acid.

[0064] Polythioethers useful for practicing the present disclosure are described, for example, in U.S. Patent Nos. 4,366,307 (Singh et al.), 4,609,762 (Morris et al.), 5,225,472 (Cameron et al.), 5,912,319 (Zook et al.), 5,959,071 (DeMoss et al.), 6,172,179 (Zook et al.), and 6,509,418 (Zook et al.).

[0065] Polythioethers can be prepared, for example, by reacting a dithiol with a diene, diyne, divinyl ether, diallyl ether, enyne, alkyne, or a combination thereof under free radical conditions. Examples of oligomeric or polymeric polythioethers useful in practicing the present disclosure are described, for example, in U.S. Patent Nos. 4,366,307 (Singh et al.), 4,609,762 (Morris et al.), 5,225,472 (Cameron et al.), 5,912,319 (Zook et al.), 5,959,071 (DeMoss et al.), 6,172,179 (Zook et al.), and 6,509,418 (Zook et al.).

[0066] Polythioethers can also be prepared, for example, by reacting a dithiol with an epoxide, which can be carried out by stirring at room temperature, optionally in the presence of a tertiary amine catalyst (e.g., 1,4-diazabicyclo[2.2.2]octane (DABCO)).

[0067] Useful polythiols can be formed by the addition of hydrogen sulfide (H2S) to carbon-carbon double bonds. For example, dipentene and triglycerides that can react with H2S. Specific examples include dipentene dimercaptan, and polythiols available as POLYMERCAPTAN 358 (mercaptanized soybean oil) and POLYMERCAPTAN 805C (mercaptanized castor oil) from Chevron Phillips Chemical Co. LLP.

[0068] Useful polythiols of this type also include those derived from the reaction of H2S (or its equivalent) with glycidyl ethers of bisphenol A epoxy resins, bisphenol F epoxy resins, and novolac epoxy resins. A preferred polythiol of this type is QX11, which is derived from a bisphenol A epoxy resin and is available under the trade name EPOMATE from Japan Epoxy Resins (JER).

[0069] The amount of the polythiol resin present in the curable composition may be 5% to 90% by weight, 10% to 80% by weight, 20% to 80% by weight based on the total weight of the curable composition, or in some embodiments, less than 5%, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, or 90% by weight, equal to this, or greater than this.

[0070] Examples of the oxidizing agent for the polysulfide resin include metal oxides such as oxides of lead, manganese, calcium, barium, sodium, and zinc. Among these, manganese(IV) oxide is particularly preferred because it provides a composition having a unique blend of hardening efficiency and rapid hardening at a desirable open time, and a product showing excellent UV properties, weather resistance, chemical resistance, and adhesion to a wide variety of substrates. Other oxidizing agents may include metal salts such as chlorates, dichromates, and permanganates of the above metals. Useful oxidizing agents cure the polysulfide resin by forming disulfide bonds.

[0071] The amount of the oxidizing agent, such as manganese(IV) oxide, in the curable composition may be 1% to 25% by weight, 2% to 20% by weight, 3% to 15% by weight based on the total weight of the curable composition, or in some embodiments, less than 1%, 2, 2.5, 3, 4, 5, 6, 7, 7.5, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25% by weight, equal to this, or greater than this.

[0072] The unsaturated compound may include at least one unsaturated compound having at least two non-aromatic carbon-carbon double bonds, at least one carbon-carbon triple bond, or a combination thereof. In some embodiments, the non-aromatic carbon-carbon double bond corresponds to a vinyl group.

[0073] Organic borane - amine complexes are latent forms of organic boranes that are released when the base is dissociated by a compound that reacts with the base, such as an acid or its equivalent. The free organic borane is, for example, an initiator capable of initiating the free radical polymerization of a curable composition.

[0074] In some embodiments, the organic borane - amine complex does not contain a thiol group. Suitable organic boranes for the organic borane - amine complex are trimethylborane, triethylborane, tri - n - propylborane, triisopropylborane, tri - n - butylborane, triisobutylborane, and tri - sec - butylborane.

[0075] Useful basic complexing agents include, for example, amines, amino alcohols, amino ethers, and compounds containing such combinations of functionalities (e.g., amino groups and alkoxy groups). Supply a complexing agent sufficient to ensure the stability of the organic borane - amine complex under ambient conditions. An excess of the basic complexing agent can be selected to still achieve desired properties such as the curing rate of the polymerizable composition and the mechanical properties of the cured composition while providing the stability of the complex under ambient conditions.

[0076] The organic borane - amine complex can be readily prepared using known techniques, such as those described in U.S. Patent Nos. 5,616,796 (Pocius et al.), 5,621,143 (Pocius), 6,252,023 (Moren), 6,410,667 (Moren), and 6,486,090 (Moren).

[0077] Suitable organoborane-amine complexes are available from suppliers such as BASF and AkzoNobel. TEB-DAP (triethylborane-1,3-diaminopropane (or 1,3-propanediamine) complex), TnBB-MOPA (tri-n-butylborane-3-methoxypropylamine complex), TEB-DETA (triethylborane-diethylenetriamine complex), TnBB-DAP (tri-n-butylborane-1,3-diaminopropane complex), and TsBB-DAP (tri-sec-butylborane-1,3-diaminopropane complex) are all available from BASF (Ludwigshafen, Germany). TEB-HMDA (triethylborane-hexamethylenediamine (also known as 1,6-hexanediamine or 1,6-diaminohexane) complex) is available from AkzoNobel (Amsterdam, Netherlands).

[0078] Organoborane-amine complexes are generally used in effective amounts, and this effective amount is an amount sufficient to readily cause a reaction (i.e., curing by polymerization and / or crosslinking) to obtain a polymer of high molecular weight sufficient for the desired end use. If the amount of organoborane produced is too small, the reaction may be incomplete. On the other hand, if this amount is too large, the reaction may proceed too rapidly to be effectively mixed, and the resulting composition may not be usable.

[0079] In other words, the effective amount of the organoborane-amine complex is at least 0.1 weight percent, or at least 0.5 weight percent. The effective amount of the organoborane-amine complex is at most 10 weight percent, or at most 5 weight percent, or at most 3 weight percent. The weight percent of boron in the composition is based on the total weight of the polymerizable material.

[0080] To activate the organoborane-amine complex, a complex dissociating agent may be included. As used herein, the term "complex dissociating agent" refers to a compound having the ability to release the organoborane from its complexing agent, thereby enabling the reaction (curing by polymerization and / or crosslinking) of the polymerizable material of the composition to be initiated. The complex dissociating agent may sometimes be referred to as an "activator" or "release promoting substance", and these terms may be used interchangeably herein.

[0081] Compounds that react rapidly with a base or an organoborane-amine complex under mild temperatures are particularly effective complex dissociating agents. Examples of such compounds include mineral acids, Lewis acids, carboxylic acids, acid anhydrides, acid chlorides, sulfonyl chlorides, phosphonic acids, isocyanates, aldehydes, 1,3-dicarbonyl compounds, acrylates, and epoxies.

[0082] Suitable complex dissociating agents include amine-reactive compounds. Amine-reactive compounds release the organoborane by reacting with the amine, thereby removing the organoborane from its chemical bond with the amine. These compounds are substances that can easily form reaction products with amines at temperatures below room temperature in order to provide compositions such as adhesives that can be easily used and cured under ambient conditions.

[0083] When present, the complex dissociating agent is typically used in an effective amount (i.e., an amount effective to promote curing by releasing the initiator from its complexing agent but not substantially adversely affecting the desired properties of the final composition). The complex dissociating agent is typically supplied in an amount such that the molar ratio of the amine-reactive groups in the complex dissociating agent to the amino groups in the complexing agent is in the range of 0.5:1.0 to 10.0:1.0, preferably in the range of 0.5:1.0 to 4.0:1.0, more preferably 1.0:1.0, although this is not essential.

[0084] Organic and inorganic peroxides can be added in any amount suitable for initiating curing. Useful organic peroxides include hydroperoxides (e.g., cumene, tert-butyl or tert-amyl hydroperoxide), dialkyl peroxides (e.g., di-tert-butyl peroxide, dicumyl peroxide, or cyclohexyl peroxide), peroxy esters (e.g., tert-butyl perbenzoate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxy-3,5,5-trimethylhexanoate, tert-butyl monoperoxymaleate, or di-tert-butyl peroxyphtalate), peroxy carbonates (e.g., tert-butyl peroxy 2-ethylhexyl carbonate, tert-butyl peroxyisopropyl carbonate, or di(4-tert-butylcyclohexyl) peroxydicarbonate), ketone peroxides (e.g., methyl ethyl ketone peroxide, 1,1-di(tert-butylperoxy) cyclohexane, 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, and cyclohexanone peroxide), and diacyl peroxides (e.g., benzoyl peroxide, or lauryl peroxide). Useful inorganic peroxides include calcium peroxide and zinc peroxide.

[0085] In some embodiments, the organic peroxide is present in an amount of from 0.05 wt% to about 10 wt% (in some embodiments, from 0.1 wt% to 5 wt%, or from 0.5 wt% to 5 wt%). The organic peroxide and its amount can be selected to provide the composition with a desired second period (i.e., the length of time that a portion of the curable composition adjacent to the surface of the aircraft remains liquid) after mixing or fusing. In some embodiments, the composition has an open time of at least 10 minutes, at least 30 minutes, at least 1 hour, or at least 2 hours.

[0086] Certain photoinitiator systems generate free radicals upon exposure to actinic radiation to cure curable compositions. The photoinitiator system can include, for example, type I and / or type II photoinitiators, sensitizers, amine co-agents, and optionally electron donors (such as in the case of three-component electron transfer photoinitiators). The actinic radiation can be within the visible spectrum or in the ultraviolet or infrared wavelength ranges and can be provided by any suitable source of electromagnetic radiation, such as a light emitting diode (LED), mercury lamp, or halogen lamp.

[0087] The photoinitiator system can include free radical photoinitiators that are sensitive to wavelengths within the visible region of the electromagnetic spectrum. Examples of such photoinitiators include, for example, acylphosphine oxide derivatives, acylphosphinate derivatives, and acylphosphine derivatives (such as phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (available as OMNIRAD 819 from IGM Resins (St. Charles, Illinois)), phenylbis(2,4,6-trimethylbenzoyl)phosphine (such as available as OMNIRAD 2100 from IGM Resins), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide (such as available as OMNIRAD 8953X from IGM Resins), isopropoxyphenyl-2,4,6-trimethylbenzoylphosphine oxide, dimethylpivaloylphosphonate), ethyl(2,4,6-trimethylbenzoyl)phenylphosphinate (such as available as OMNIRAD TPO-L from IGM Resins); and bis(cyclopentadienyl)bis[2,6-difluoro-3-(1-pyrryl)phenyl]titanium (such as available as OMNIRAD 784 from IGM Resins).

[0088] Optionally, the curable composition contains one or more basic compounds. These include amines such as 1,4-diazabicyclo[2.2.2]octane (DABCO), 1,2-dimethylimidazole, 3-quinuclidinol, and / or excess amines provided by organoborane-amine complexes, and / or one or more inorganic bases such as inorganic bases (e.g., magnesium hydroxide, sodium hydroxide, calcium hydroxide, calcium oxide, and sodium carbonate). When included, typical amounts are from 0.1 to 8 weight percent, preferably from 0.2 to 2 percent, but this is not essential.

[0089] Examples of suitable curable compositions can be found in PCT International Publication No. WO 2013 / 151893 (Ye), WO 2014 / 164103 (Ye), WO 2014 / 164244 (Ye), WO 2014 / 172302 (Zook), WO 2014 / 172305 (Zook), WO 2016 / 106352 (Ye), WO 2016 / 106364 (Swan), WO 2016 / 130673 (Demoss), WO 2016 / 176537 (Zook), WO 2016 / 176548 (Ye), and WO 2017 / 015188 (Blackwell), as well as U.S. Patent No. 9,650,150 (Zook), and U.S. Patent Application No. 62 / 66,709 (Moser).

[0090] Advantageously, it is possible to embed in the curable composition a light-transmissive film, fiber, and / or particles that can assist in transmitting actinic radiation through the curable composition. In some embodiments, for example, the curable composition includes a plurality of microspheres. The microspheres may be solid or hollow, may be resistant to compression, and can set the maximum compression level of the curable composition. The microspheres can be made of glass. The glass microspheres can also be useful for assisting in the transmission of actinic radiation, such as blue light, through the curable composition. This can help promote curing at locations blocked by non-transparent materials (e.g., aircraft parts as described herein) within the curable composition, or can help promote curing at locations where the actinic radiation in the curable composition penetrates too deeply.

[0091] Other materials, such as hollow filaments or woven fabric hollow filament fabrics, can be included in the curable composition to assist in the transmission of actinic radiation through the curable composition. Any of the glass microspheres of the filaments can extend from the outer edge or surface of the curable composition to any desired depth within the curable composition.

[0092] The microspheres can also be used to modify the viscosity of the curable composition. Any other suitable viscosity modifier can be used as well. The viscosity of the curable composition can be any suitable value. For example, the viscosity can be a value such that the curable composition can flow, deform in the uncured state, and substantially retain its form when at least partially cured. As an example, at ambient conditions (e.g., a temperature of about 25 °C), the viscosity of the curable composition is in the range of about 3,000 Pa·s to about 10,000 Pa·s, about 5,000 Pa·s to about 8,000 Pa·s, or is about 3,000 Pa·s, 3,500, 4,000, 4,500, 5,000, 5,500, 6,000, 6,500, 7,000, 7,500, 8,000, 8,500, 9,000, 9,500, or less than, equal to, or greater than about 10,000 Pa·s. The viscosity can be measured using a HAAKE RheoWin instrument, although there are other instruments that are equally well suited for measuring viscosity.

[0093] The shim patterns described herein can have any suitable dimensions. For example, the width and length of the shim pattern can be independently selected from about 1.2 cm to about 40 cm, about 5 cm to about 20 cm, about 10 cm to about 15 cm, or are about 1.2 cm, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20, 20.5, 21, 21.5, 22, 22.5, 23, 23.5, 24, 24.5, 25, 25.5, 26, 26.5, 27, 27.5, 28, 28.5, 29, 29.5, 30, 30.5, 31, 31.5, 32, 32.5, 33, 33.5, 34, 34.5, 35, 35.5, 36, 36.5, 37, 37.5, 38, 38.5, 39, 39.5, and less than about 40 cm, or equal to or greater than this. The thickness of the shim can have any of the dimensions listed above with respect to the gap thickness.

[0094] The curable composition can include one or more additional non-uniform fillers. Such fillers include glass fibers, aluminum silicate (mullite), synthetic calcium silicate, zirconium silicate, fused silica, crystalline silica graphite, natural silica sand; boron powder, for example, boron nitride powder, boron silicate powder; oxides, such as TiO2, aluminum oxide, magnesium oxide, zinc oxide; calcium sulfate (as its anhydride, dehydrate, or trihydrate); calcium carbonate, for example, chalk, limestone, marble, synthetic precipitated calcium carbonate; talc including fibrous talc, modular talc, acicular talc, layered talc; wollastonite; surface-treated wollastonite; glass spheres, for example, hollow and solid glass spheres, silicate spheres, cenospheres, aluminosilicate (armospheres); kaolin including hard kaolin, soft kaolin, calcined kaolin; single crystal fibers or “whiskers,” such as silicon carbide, alumina, boron carbide, iron, nickel, copper; fibers (including long fibers and short fibers), for example, asbestos, carbon fibers; sulfides, such as molybdenum sulfide, zinc sulfide; barium compounds, such as barium titanate, barium ferrite, barium sulfate, barite; metals (for example, metal mesh, metal plate) and metal oxides, such as particulate or fibrous aluminum, bronze, zinc, copper, and nickel; flaky fillers, such as glass flakes, flaky silicon carbide, aluminum diboride, aluminum flakes, steel flakes; fibrous fillers, such as inorganic short fibers derived from a blend including at least one of aluminum silicate, aluminum oxide, magnesium oxide, and calcium sulfate hemihydrate; natural fillers and reinforcing materials, such as wood powder obtained by pulverizing wood, kenaf, cellulose, cotton, sisal, jute, flax, starch, corn flour, lignin, ramie, straw, sugarcane, bamboo, hemp, pulverized nut shells, corn, coconut (coir), rice husks, and other fibrous products;Fibrous reinforcing organic fillers formed from organic polymers capable of forming fibers such as organic fillers like polytetrafluoroethylene, poly(ether ketone), polyimide, polybenzoxazole, poly(phenylene sulfide), polyester, polyethylene, aromatic polyamide, aromatic polyamide, polyetherimide, polytetrafluoroethylene, acrylic resin, poly(vinyl alcohol), etc.; and fillers such as mica, clay, feldspar, soot, fillite, quartz, diatomaceous earth, perlite, diatomaceous earth, carbon black, or combinations including at least one of the aforementioned fillers. The filler can be surface-treated with silane, siloxane, or a combination of silane and siloxane to improve adhesion and dispersion.;

[0095] The amount of any of the above fillers may be 10 wt% - 95 wt%, 20 wt% - 90 wt%, 30 wt% - 80 wt% based on the total weight of the curable composition, or in some embodiments, less than 10 wt%, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, or 95 wt%, equal to this, or greater than this. The aforementioned amounts can be applied to a single filler or the total of all fillers.;

[0096] As described herein, the curable composition can include glass microspheres. Examples of glass microspheres are 3M Glass Microspheres from 3M Company or the ECCOSPHERES brand of hollow glass microspheres from Trelleborg AB (Trelleborg, Sweden). Such fillers can significantly reduce the density of the composition while maintaining acceptable mechanical properties after curing. Advantageously, by including hollow filler particles, the density of the composition can be significantly reduced, and thus, in practice, the total weight of the composition can be reduced. The density of the filler particles is 0.18 g / cm 3is 0.3, 0.5, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, or less than 2 but equal to or greater than these values.

[0097] Although not intended to be exhaustive, specific embodiments of how to insert these shims are listed below.

[0098] 1. A method of manufacturing a structural shim installed between a first part and a second part of an assembly, comprising disposing a hardenable composition within a gap between the first part and the second part; hardening the hardenable composition to provide a dimensionally stable shim pattern; removing the shim pattern from the gap, the removal being capable of removing the shim pattern from the gap without damage; and fabricating a structural shim using the shim pattern.

[0099] 2. The method according to embodiment 1, wherein the assembly is an aircraft, the first part is an outer panel of the aircraft, and the second part is a basic structure of the aircraft.

[0100] 3. The method according to embodiment 1 or 2, wherein fabricating a structural shim using the shim pattern includes creating a digital model of the shim pattern and then fabricating a structural shim using the digital model.

[0101] 4. The method according to any one of embodiments 1 to 3, wherein the residual contamination remaining on the outer panel or the basic structure by removing the shim pattern from the gap is essentially zero.

[0102] 5. The method according to any one of embodiments 1 to 4, wherein the hardenable composition is an extrudable composition.

[0103] 6. The method according to any one of embodiments 1 to 5, wherein the hardenable composition is a liquid at ambient temperature.

[0104] 7. The method according to any one of Embodiments 1 to 6, wherein the hardenable composition is dimensionally stable at ambient temperature.

[0105] 8. The method according to Embodiment 7, wherein the hardenable composition is provided in the form of a film or a sheet.

[0106] 9. The method according to any one of Embodiments 1 to 8, wherein the hardenable composition is a curable composition, and hardening the hardenable composition includes curing the curable composition.

[0107] 10. The method according to Embodiment 9, wherein the curable composition includes first and second components, and the curable composition is cured by mixing the first and second components with each other.

[0108] 11. The method according to Embodiment 9, wherein the curable composition is cured by exposure to actinic radiation, and the exposure to actinic radiation is provided by transmitting actinic radiation through a plurality of films, fibers, and / or particles embedded in the curable composition.

[0109] 12. The method according to Embodiment 9, wherein the curable composition is cured by heating the curable composition to a curing temperature above ambient temperature.

[0110] 13. The method according to any one of Embodiments 1 to 12, wherein the structural shim is fabricated by an additive manufacturing process or a subtractive manufacturing process.

[0111] 14. A method of joining an outer skin and a basic structure of an aircraft, the method including manufacturing a structural shim according to any one of the methods of Embodiments 1 to 13, inserting the structural shim between the outer skin and the basic structure, and securing the outer skin and the basic structure to each other.

[0112] 15. A method of manufacturing a shim pattern for manufacturing a structural shim installed between the outer skin and the basic structure of an aircraft, the method comprising: disposing a hardenable composition within a gap between the outer skin and the basic structure; hardening the hardenable composition to provide a shim pattern, the shim pattern being dimensionally stable; and removing the shim pattern from the gap, the shim pattern being removable from the gap without damage.

Example

[0113] The objects and advantages of the present disclosure are further illustrated by the following non-limiting examples, but the specific materials and their amounts cited in these examples, as well as other conditions and details, should not be construed as unduly limiting the present disclosure.

[0114] Unless otherwise specified, all parts, percentages, ratios, etc. in the examples and elsewhere in this specification are by weight.

Table 1

[0115] Test method: Viscosity The viscosity of the sample was measured according to the method described in ASTM D2196-10. The sample was stabilized at 77°F (25°C) for at least 8 hours before measurement. The sample was stirred by hand for 3 minutes, allowed to stand for 60 minutes, and the viscosity was determined using a DV2T rotational viscometer equipped with a No. 7 spindle rotating at 2 revolutions per minute (RPM) obtained from AMETEK Brookfield (Middleboro, MA, USA).

[0116] Density The density of the sample was measured according to the method described in ASTM D792-13. The sample was stabilized at 77°F (25°C) for at least 24 hours before measurement. The weights of the sample in air and water were measured using an XS104 Analytical Balance equipped with a density kit obtained from METTLER Toledo (Columbus, OH, USA).

[0117] Hardness measurement Samples were produced by applying a sealant to an open mold made of polytetrafluoroethylene (PTFE) with cavity dimensions of 9.525 cm × 4.064 cm × 0.318 cm (3.75 inches × 1.6 inches × 0.125 inches). Excess sealant was scraped off using a flat-blade tool so that the top and bottom surfaces of the applied sealant were approximately parallel.

[0118] The instantaneous hardness was determined in accordance with ASTM D2240 using a Model 2000 Type A Durometer obtained from Rex Gauge Company (Buffalo Grove, IL, USA) after curing the sample under given conditions. The measurements were obtained for two 0.318 cm (0.125 inch) thick test specimens laminated back-to-back (for "upper hardness" measurement) or face-to-face (for "bottom hardness" measurement). If the thickness was less than 0.318 cm (0.125 inch), multiple pieces were laminated so as to obtain a total thickness of at least 0.635 cm (0.25 inch).

[0119] Example 1: Step 1: Preparation of Component A of the polysulfide pattern compound The Agent A was prepared by using a spatula to mix MnO2 and MT in a MAX 200 DAC cup (FlackTek, Inc. (Landrum, SC, USA)) at the weight percentages specified in Table 1. Then, using a SPEEDMIXER model DAC 400 FVZ (FlackTek, Inc.), the contents of the cup were mixed at 1600 revolutions per minute (RPM) for 60 seconds. The sides and bottom of the cup were scraped with a spatula, and the contents of the cup were mixed for an additional 30 seconds at 1600 RPM. Next, ZnSt and CB were added to the DAC cup at the weight percentages specified in Table 1, and all the raw materials were mixed for an additional 60 seconds at 1600 RPM. The resulting hardener component had a viscosity of 1350 poises at 25 °C (77 °F) and a density of 1.58 g / cm 3 of.

Table 2

[0120] Step 2: Preparation of Agent B of the polysulfide pattern compound Agent B was prepared in a manner similar to Agent A. Using a spatula, PS, S322, TiO2, HT, RB, and TETD were mixed in a MAX 200 DAC cup at the weight percentages specified in Table 2. Then, using a DAC 400 FVZ SPEEDMIXER, the contents of the cup were mixed at 1600 RPM for 60 seconds. The sides and bottom of the cup were scraped with a spatula, and the contents were mixed for an additional 30 seconds at 1600 RPM. The resulting base component had a viscosity of 11,200 poises at 25 °C (77 °F) and a density of 1.51 g / cm 3 of, and the color was red.

Table 3

[0121] Step 3: Mixing of the polysulfide pattern compound Using a spatula, 10 grams of Agent A and 100 grams of Agent B were mixed in a MAX 200 DAC cup. Then, using a DAC 400 FVZ SPEEDMIXER, the contents of the cup were mixed at 1600 RPM for 60 seconds. The sides and bottom of the cup were scraped with a spatula, and the contents were mixed at 1600 RPM for an additional 30 seconds.

[0122] Step 4: Testing of the polysulfide pattern compound A 25-gram portion of the mixed composition was placed in the shim gap between two mating parts of an aircraft structure. The resulting rubbery gap pattern had a Shore A hardness of 55, showed no adhesion to the aircraft parts, and provided a nominal map of the required shim profile and outer shape.

[0123] Example 2: Step 1: Preparation of the curing agent (Agent A) Using a spatula, PET and DABCO were mixed in a MAX 200 DAC cup at the weight percentages specified in Table 3, and Agent A was prepared by heating at 60°C for 2 hours. The mixture was cooled to room temperature, and the remaining raw materials: R-202, S322, D-E135, and TnBB-MOPA were added to the DAC cup at the weight percentages specified in Table 3. Then, using a DAC 400 FVZ SPEEDMIXER, the raw materials were mixed at 1600 RPM for 60 seconds. The sides and bottom of the cup were scraped with a spatula, and the raw materials were mixed at 1600 RPM for an additional 30 seconds.

Table 4

[0124] Step 2: Preparation of the base agent (Agent B) Using a DAC 400FVZ SPEEDMIXER, Agent B was prepared by mixing the raw materials specified in Table 4 in a MAX 200 DAC cup at 1600 RPM for 60 seconds. The sides and bottom of the cup were scraped with a spatula, and the contents were mixed at 1600 RPM for an additional 30 seconds.

Table 5

[0125] Step 3: Mixing of the hardener (Agent A) and the base (Agent B) Using a spatula, 90.92 grams of Agent A and 10.34 grams of Agent B were mixed in a MAX 200 DAC cup. Then, using a DAC 400 FVZ SPEEDMIXER, the cup was mixed at 1600 RPM for 30 seconds. The sides and bottom of the cup were scraped with a spatula, and the contents were mixed at high speed at 1600 RPM for an additional 30 seconds.

[0126] Step 4: Testing of the pattern compound A 25-gram portion of the mixed composition was placed in the shim gap between two mating parts of an automotive door structure. The exposed portion of the pattern compound was irradiated for 60 seconds using a 450-nm LED curing lamp (3M ELIPAR DeepCure-S Light, 3M Company (St. Paul, MN, USA)). During the next 8 hours, the remaining non-irradiated portion of the pattern compound was fully cured into a rubbery mass. The resulting gap pattern showed no adhesion to the automotive door parts, had a Shore A hardness of 45, and provided a nominal map of the required shim profile and outer shape. * * *

[0127] All references, patents, and patent applications cited in the above patent application are hereby incorporated by reference in their entirety in a consistent manner. In the event of any inconsistencies or contradictions between the incorporated reference portions and this application, the information in the foregoing description shall prevail. The foregoing description is for the purpose of enabling a person skilled in the art to practice the disclosure set forth in the claims and should not be construed as limiting the scope of the present disclosure, which is defined by the claims and all their equivalents.

Claims

1. A method for manufacturing a structural shim installed between a first component and a second component of an assembly, comprising: placing a hardenable composition within a gap between the first component and the second component, wherein the first component and the second component each have a mating surface that defines the gap therebetween, and the hardenable composition is in direct contact with the mating surfaces of the first component and the second component; hardening the hardenable composition to provide a dimensionally stable shim pattern; removing the shim pattern from the gap, wherein the shim pattern is removable from the mating surfaces that define the gap; and fabricating the structural shim using the dimensions of the shim pattern. The structural shim has a size and shape such that it fills the gap while maintaining separation and relative orientation of the mating surfaces. The hardenable composition comprises a polythiol. The structural shim has a size and shape such that it fills the gap while maintaining separation and relative orientation of the mating surfaces. The hardenable composition comprises a polythiol. Method.

2. The method according to claim 1, wherein the assembly is an aircraft, the first component is an outer skin of the aircraft, and the second component is a basic structure of the aircraft.

3. The method according to claim 1 or 2, wherein the hardenable composition is a liquid at ambient temperature.

4. The method according to claim 1 or 2, wherein the hardenable composition is dimensionally stable at ambient temperature.

5. The method according to claim 4, wherein the hardenable composition is provided in the form of a film or sheet.

6. The method according to any one of claims 1 to 5, wherein the hardenable composition is a curable composition, and hardening the hardenable composition includes curing the curable composition.

7. A method for joining an outer skin and a basic structure of an aircraft, comprising: manufacturing a structural shim according to the method of any one of claims 1 to 6; inserting the structural shim between the outer skin and the basic structure; and securing the outer skin and the basic structure to each other.

8. A method for manufacturing a shim pattern for fabricating a structural shim installed between an outer skin and a basic structure of an aircraft, comprising: placing a hardenable composition within a gap between the outer panel and the underlying structure, where the outer panel and the underlying structure each have a mating surface that defines the gap therebetween, and the hardenable composition is in direct contact with the mating surfaces of the outer panel and the underlying structure, hardening the hardenable composition to provide the shim pattern, the shim pattern being dimensionally stable, removing the shim pattern from the gap, the shim pattern being removable from the mating surface that defines the gap, wherein the hardenable composition includes a polythiol, method.

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