Method for manufacturing composite material articles, and composite material articles 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 of related applications This application claims priority under U.S. Provisional Application No. 63 / 210,168, filed on 14 June 2021, the entire contents of which are incorporated herein by reference.

[0002] This invention relates to a method for manufacturing composite material articles and composite material articles manufactured thereby. The method described herein utilizes a curable composition comprising an NCF fabric having a specific type of suture. The curable compositions and composite material articles manufactured according to this disclosure are particularly suitable for manufacturing composite material components for use in many applications, such as aerospace, automotive, and marine applications. [Background technology]

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

[0004] The advancement of FRP composite materials is attributed to various factors, including the need for alternatives to metals and lightweight materials with a desirable balance of properties, including toughness and chemical resistance. More specifically, by maintaining and even enhancing the desirable properties of FRP composite materials while simultaneously reducing overall weight, problems associated with metal fatigue and corrosion can be eliminated, resulting in the manufacture of more fuel-efficient aircraft, automobiles, transport vehicles, and ships, as well as their components, without sacrificing performance. Furthermore, by manufacturing aircraft, vehicle, and ship components and elements using FRP composite materials, not only can the overall weight of aircraft, vehicle, and ship be reduced, but the time required for manufacturing and processing of components and elements can also be shortened. Similarly, in construction and infrastructure applications, FRP composite materials can provide alternative materials to conventional building and construction materials while reducing and maintaining the overall cost, weight (and associated stresses and loads), and construction time (i.e., through prefabrication processes).

[0005] To manufacture FRP composite materials, reinforcing fibers, which can be provided in various forms such as non-crimped fibers, are combined with a matrix resin. This combination is then typically cured in a mold at a predetermined temperature and pressure to form the final FRP composite material. However, the resulting FRP composite material may lack the strength and toughness desired for specific applications, particularly aerospace applications.

[0006] Non-crimped 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. These fibers, filaments, or yarns are also called reinforcing fibers, filaments, or yarns. Such non-crimped fabrics may further comprise one or more interlayers, each of which may include, for example, webs, woven fabrics, bales, or scrims. The layers are typically joined together by sutures.

[0007] Composite material components, such as NCF composites, are often subjected to thermal cycling and high-humidity periods when used in a variety of applications. Due to temperature changes, such composite components experience expansion and contraction in various directions, depending on the coefficient of thermal expansion (CTE), which is dependent on the orientation of the plies. If expansion or contraction occurs carefully in independent, stress-free plies, no stress is generated regardless of the ply orientation. However, when plies are rotated to different orientations and laminated together, the stress in adjacent plies prevents each ply from expanding or contracting according to its own CTE. This results in high stress in the plies. Because the matrix has a lower intra-system fracture stress than the fibers, microcracks typically develop within the matrix. Furthermore, the introduction of sutures, typically used to fix plies together, is known to create areas near the sutures where microcracks are more likely to form as a result of ply expansion or contraction. Microcracks can cause significant changes in properties such as stiffness. Therefore, mitigating microcrack formation is a research challenge in this field.

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

[0009] Therefore, there is an ongoing need to mitigate or prevent the occurrence of microcracks in composite material components exposed to moist thermal stress, particularly components manufactured from NCF. This specification describes a novel strategy for suppressing the microcrack behavior of composite material articles, wherein a specific curable composition is cured according to the method of the present invention. [Overview of the project]

[0010] This objective, and 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 for manufacturing a composite material article, the method comprising: a) providing a curable composition comprising a matrix resin and a non-shrinking fabric, the non-shrinking fabric comprising at least one layer of unidirectionally oriented multifilament carbon yarns and multifilament stitching yarns interconnecting the multifilament carbon yarns, the stitching yarns comprising a thermoplastic polymer and having a linear density of 80 dtex or less; b) heating the curable composition to a temperature T1, where T1 is higher than the melting temperature (T m ) of the stitching yarns, or the conversion rate of the matrix resin at T1 is 30% or less, typically 20% or less, more typically 10% or less; m c) maintaining the temperature T1 for a time sufficient for the curable composition to cure, or heating to a temperature T2, thereby manufacturing a composite material article.

[0012] In a second aspect, the present disclosure relates to a composite material article manufactured according to the method described herein.

Brief Description of the Drawings

[0013] [Figure 1] Shows an accelerated hygrothermal load representing operating conditions typical of the life cycle of a subsonic jet.

Embodiments of the Invention

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

[0015] ​​As used herein, the term "and / or" when used in the phrase "A and / or B" means only A, only B, 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 specification pertains.

[0018] As used herein, unless otherwise indicated, the term "about" or "approximately" means an acceptable error for a particular value 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" means within 1, 2, 3, or 4 standard deviations. In certain embodiments, the term "about" or "approximately" means 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] Also, it will be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, the range "1 to 10" is intended to include all sub-ranges between and including the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value of 1 or more and a maximum value of 10 or less. Since the disclosed numerical ranges are continuous, all values between the minimum and maximum values are included. Unless otherwise specified, the various numerical ranges specified in this application are approximate values.

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

[0021] In a first aspect, the disclosure relates to a method for manufacturing a composite material article, the method being: a) To provide a curable composition comprising a matrix resin and a non-crimped fabric, wherein the non-crimped fabric comprises at least one layer of unidirectionally oriented multifilament carbon yarns and multifilament sutures connecting the multifilament carbon yarns, and the sutures contain a thermoplastic polymer and have a linear density of 80 dtex or less; b) Heating the curable composition to a temperature T1, wherein T1 is the melting temperature of the suture (T m ) is higher than T m Or the conversion rate of the curable composition at T1 is 30% or less, typically 20% or less, more typically 10% or less; and c) Maintaining a temperature T1 for a sufficient time for the curable composition to cure, or heating it to a temperature T2, thereby producing a composite material article. Includes.

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

[0023] The term “non-crimped fabric” or “non-crimped fabric” is sometimes referred to as “NCF” and refers to a structure comprising 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., one direction). Multiple layers can be laminated such that the fibers, filaments, or yarns of one layer are oriented parallel to the fibers, filaments, or yarns of an adjacent layer, or intersect with the fibers, filaments, or yarns of an adjacent layer. When the fibers, filaments, or yarns of one layer are oriented to intersect with the fibers, filaments, or yarns of an adjacent layer, the angle between the axis of one layer (the axis is determined by the direction of the fibers, filaments, or yarns of the layer) and the axis of an adjacent layer is virtually infinitely adjustable. For example, the angle between adjacent fiber layers may be 0° or 90°, or such angles may be plus or minus 25°, plus or minus 30°, plus or minus 45°, or plus or minus 60°, and the 0° direction is determined by a method known to those skilled in the art. For example, the machine direction may be designated as the 0° direction. Therefore, the term "multiaxial" refers to NCF fabrics that have two or more layers, each oriented in different directions. Multiaxial fabrics include biaxial fabrics, where the layers are oriented in two directions, and triaxial fabrics, where the layers are oriented in three directions. For example, multiaxial non-crimped fabrics can be manufactured using warp knitting machines or stitch bonding machines.

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

[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, where these layers are oriented in the same direction. In another embodiment, the non-crimped fabric comprises two or more layers of unidirectionally oriented multifilament carbon yarns, where these layers are oriented in different directions.

[0027] In this specification, yarn means one or more fibers, one or more filaments, or a continuous strand of material in a form suitable for use in the manufacture of fabrics, sewing, crocheting, knitting, weaving, sewing, etc. Yarns include, for example, (1) multiple filaments that are joined together or bundled without twisting or intentionally twisting (sometimes called zero-twist yarn or untwisted yarn); (2) multiple filaments that are joined together or bundled and are entangled, falsely twisted, or bulked in some way; (3) multiple filaments that are joined together or bundled with some degree of twist (sometimes called twisted yarn); (4) a single filament, with or without twist (sometimes called monofilament or monofilament yarn); bulked yarns may be filaments or spun yarns that have been given a significantly larger volume by physical, chemical, or thermal treatment, or a combination thereof. In some cases, yarn is called filament yarn or multifilament yarn, both of which are generally yarns made from multiple filaments.

[0028] As used herein, “fiber” refers to a material with a high length-to-thickness ratio. The fibers may be continuous, in which case such fibers are called filaments or staple lengths (i.e., individual lengths).

[0029] Therefore, in one embodiment, the suture includes one or more thermoplastic fibers or filaments.

[0030] The unidirectionally oriented multifilament carbon threads within a single layer of the NCF of this 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, thereby reducing the size of undesirable resin-rich zones in composite articles manufactured from the NCF fabric.

[0031] The suture contains 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. Examples of 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 includes polyamide, polyester, or a blend or copolymer thereof.

[0034] 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 semicrystalline polymer.

[0036] The suture has a melting temperature, i.e., T m It can be characterized by the following: In one embodiment, the suture has a melting temperature of 230°C or less, typically 220°C or less. In another embodiment, the melting temperature of the suture is 70°C to 200°C, typically 90°C to 180°C.

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

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

[0039] The fibers or filaments of the multifilament sewing thread can be characterized by density. The density used herein refers to the density of the polymeric material used in the manufacture of the fibers. The fibers or filaments of the multifilament sewing thread have a density of 0.5 to 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 sewing thread have a density of 0.9 to 1.4 g / cm 3 .

[0040] The number of filaments used herein is the number of filaments constituting the thread. The number of filaments of the multifilament sewing thread is 1.0 times or less of the dtex value of the thread, typically 0.9 times or less of the dtex value of the thread, more typically 0.8 times or less of the dtex value of the thread.

[0041] In some embodiments, the number of filaments is in the range of 0.1 to 0.8 times the dtex value of the thread, typically 0.1 to 0.6 times the dtex value of the thread, more typically 0.1 to 0.5 times the dtex value of the thread.

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

[0043] Sutures can also be characterized by their twist. In this specification, twist refers to the helical arrangement of fibers or filaments around the axis of the thread. The multifilament sutures of this disclosure may or may not have twist. If twist is present, it is indicated as the number of turns per unit length, typically per meter. Multifilament sutures typically 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, and 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 fastened to one another by a plurality of sutures or knitting threads, for example, arranged parallel to each other and running parallel to each other to form a seam, in accordance with methods known to those skilled in the art. The sutures or knitting threads used to connect and fasten the layers of the multiaxial NCF fabric may be the same as or different from the multifilament sutures described herein. In one embodiment, the sutures or knitting threads used to connect and fasten the layers of the multiaxial NCF fabric are the same as the multifilament sutures described herein.

[0045] Multifilament sutures do not provide structural reinforcement by holding unidirectionally oriented multifilament threads integrally within a single layer of NCF and / or fixing two or more layers of NCF fabric together. Therefore, multifilament sutures used according to this disclosure to interconnect unidirectionally oriented multifilament carbon threads within a single layer of NCF and / or to integrate two or more layers within NCF fabric are non-structural. In contrast, unidirectionally oriented multifilament carbon threads are structural because they provide structural reinforcement to composite materials or articles manufactured therefrom.

[0046] Non-crimped fabrics may further include one or more layers of bale, typically nonwoven bale. For example, a non-crimped fabric may include a layer of unidirectionally oriented multifilament carbon yarn combined with a layer of bale. Any bale known to those skilled in the art can be used. The layers constituting the NCF fabric, including one or more layers of bale, can be connected and fixed to each other according to methods known to those skilled in the art, such as by multiple sutures or knitting threads. When used, the bale layers advantageously improve process properties such as permeability, and mechanical properties such as impact resistance and delamination resistance. Illustrative bale materials that may be used are described in PCT International Publication No. 2017 / 083631 and International Publication No. 2016 / 003763, which are incorporated by reference. The bale can be manufactured from materials known to those skilled in the art.

[0047] Non-crimped fabrics can be obtained from commercial suppliers or manufactured according to methods known to those skilled in the art. To form a single layer of NCF, unidirectionally oriented multifilament carbon yarns can be interconnected. Multiple such single layers of NCF can be combined to form a multilayer NCF fabric in which multiple layers are interconnected using the sutures described herein.

[0048] The interconnection of unidirectionally oriented multifilament carbon threads within a single layer of NCF, and / or the integration of two or more layers in an NCF fabric, can be achieved using various stitch types, stitch widths (i.e., distances between points in the weft direction), and stitch lengths (i.e., distances 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 the usable stitch widths and stitch lengths. For example, the stitch width may be in the range of 1 to 20 mm, typically 1 to 10 mm. The stitch length may be in the range of 1 to 20 mm, typically 1 to 10 mm.

[0049] If the NCF fabric comprises two or more layers, the layers can be connected and secured to each other by sewing or knitting according to known methods using sutures such as the multifilament sutures described herein. If the NCF fabric is multiaxial, the manufacture of such multiaxial NCF is known, and the prior art described, for example, 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 is utilized.

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

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

[0052] The support structure may further include layers of any type of textile product known to those skilled in the art for manufacturing composite materials. Examples of suitable fabric types or configurations include, but are not limited to, all woven fabrics (examples being plain weave, twill weave, satin weave, spiral weave, and monofilament fabrics); warp-knitted fabrics; knitted fabrics; braided fabrics; all nonwoven fabrics (examples including, but are not limited to, nonwoven bales, mat fabrics made of chopped fibers and / or continuous fiber filaments, felt, etc.), as well as combinations of the aforementioned fabric types.

[0053] In one embodiment, the support structure may further include a bale, typically a nonwoven bale. Any bale known to those skilled in the art can be used. For example, the bale described in PCT International Publication 2017 / 083631 can be used. The binder component can be distributed on at least one side of the bale layer or through a portion of the bale, or distributed throughout the entire non-crimped fabric, including the inter-fiber spaces oriented in one direction and a portion of the bale. For example, the binder described in PCT International Publication 2016 / 003763 (which is incorporated herein by reference) can be used. The binder may be present in an amount of 15% by weight or less of the final fabric. Typically, the binder component does not form a continuous film on the surface of the fibrous material. The bale can be manufactured from materials known to those skilled in the art. For example, the bale can be manufactured from the same material as the sutures described herein.

[0054] Available liquid molding processes include, but are not limited to, vacuum-assisted resin transfer molding (VARTM), which uses the differential pressure created by a vacuum to inject resin into a support structure. Another method is resin transfer molding (RTM), in which resin is pressurized and injected into a support structure in a sealed mold. A third method is resin film injection (RFI), in which a semi-solid resin is placed below or above the support structure, appropriate tools are positioned on the part, the part is placed in a bag, and then melted in an autoclave to inject the resin into the support structure.

[0055] The matrix resins for impregnation, injection, or injection into the support structures described herein include curable resins and optionally include suitable additives known to those skilled in the art. In this disclosure, “curing” or “cure” means the solidification of a polymer material by chemical crosslinking of polymer chains. With respect to compositions, the term “curable” means that the composition can be subjected to conditions that result in a solidified state. 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 phenol), polyesters, acrylics, hybrids, blends, and combinations thereof.

[0057] Suitable epoxy resins include aromatic diamines, aromatic monoprimary amines, aminophenols, polyhydric phenols, polyhydric alcohols, glycidyl derivatives of 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 cresol and phenolic novolacs; glycidyl ethers of phenol-aldehyde adducts; glycidyl ethers of aliphatic dials; diglycidyl ethers; diethylene glycol diglycidyl ethers; aromatic epoxy resins; aliphatic polyglycidyl ethers; epoxidized olefins; brominated resins; aromatic glycidylamines; heterocyclic glycidylimides and amides; glycidyl ethers; fluorinated epoxy resins; or combinations thereof.

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

[0059] Suitable oxetane compounds that contain at least one oxetano group per molecule include, for example, 3-ethyl-3[[(3-ethyloxetane-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 includes 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 elastic polymers as reinforcing agents, stabilizers, inhibitors, pigments, dyes, flame retardants, reactive diluents, UV absorbers, and other additives known to those skilled in the art for improving 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 alicyclic 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, and 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 Examples of suitable curing agents include alicyclic amines such as cyclohexane (DACH), isophorone diamine (IPDA), 4,4'-diaminodicyclohexylmethane (PACM), bisaminopropylpiperazine (BAPP), and 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, chloridenic anhydride, and trimellitic anhydride.

[0063] Furthermore, other curing agents are Lewis acid:Lewis base complexes. Suitable Lewis acid:suitable base complexes include, for example, BCl3:amine complexes, BF3:amine complexes, for example, BF3:monoethylamine, BF3:propylamine, BF3:isopropylamine, BF3:benzylamine, BF3:chlorobenzylamine, BF 3: Examples of complexes include trimethylamine, BF3:pyridine, BF3:THF, AlCl3:THF, AlCl3:acetonitrile, and ZnCl2:THF.

[0064] Additional curing agents include polyamides, polyamines, amidoamines, polyamidoamines, polyalicyclic compounds, polyetheramides, imidazoles, dicyandiamides, substituted ureas and urones, hydrazines and silicones.

[0065] Urea-based curing agents include materials available under the trade name DYHARD (sold by Alzchem), and urea derivatives such as those commercially available as UR200, UR300, UR400, UR600, and UR700. Examples of uron accelerators include 4,4-methylenediphenylenebis(N,N-dimethylurea) (available from Onmicure as U52M).

[0066] If 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, and more typically in the range of 20% to 30% by weight.

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

[0068] If present, reinforcing particles or reinforcing agents may be present in an amount of 0.1% to 30% by weight of the resin composition. In one embodiment, reinforcing particles or reinforcing agents may be present in an amount of 10% to 25% by weight. In another embodiment, reinforcing particles or reinforcing agents may be present in an amount of 0.1% to 10% by weight. Suitable reinforcing particles or reinforcing agents include, for example, Virantage VW10200FRP, VW10300FP and VW10700FRP from Solvay, and BASF UltrasonE2020 and Sumikaexcel5003P from Sumitomo Chemical.

[0069] The reinforcing particles or reinforcing agents may be in the form of particles with a diameter of 5 microns or less, typically 1 micron or less. The size of the reinforcing particles or reinforcing agents can be selected so as not to be filtered by the fiber reinforcing material. Optionally, the composition may also contain silica gel, calcium silicate, silica oxide, phosphate, molybdate, fumed silica, amorphous silica, amorphous fused silica, clay such as bentonite, organic clay, aluminum trihydrate, hollow glass microspheres, hollow polymer microspheres, microballoons, and calcium carbonate.

[0070] The composition may also contain conductive particles, such as those described in PCT International Publication No. 2013 / 141916, International Publication No. 2015 / 130368, and International Publication No. 2016 / 048885.

[0071] The carbon in multifilament carbon yarn may be in the form of graphite. The carbon may be metallized with discontinuous or continuous metal layers. Graphite fibers that have been found particularly useful in the present invention are those supplied by Solvay under trade names T650-35, T650-42, and T300; those supplied by Toray under trade names T700, T800, and T1000; and those supplied by Hexcel under 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] The mold for resin injection may be a sealed mold with two components, or a single-sided mold sealed with a vacuum back.

[0073] Curable compositions can be manufactured according to any suitable method known to those skilled in the art. One suitable method for preparing a curable composition involves supplying a support structure into a mold and then injecting or injecting the matrix resin described herein into one or more layers of a non-crimped fabric. Typically, the support structure and / or matrix resin are at a specific temperature during the injection or injection process. Herein, “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, curable compositions may be supplied at a specific injection temperature typically higher than the ambient temperature, i.e., higher than 25°C.

[0074] In step b) of the method, the curable composition is heated to a temperature T1, where T1 is the melting temperature of the suture (T m ) is higher than T m Alternatively, the conversion rate of the curable composition at T1 is 30% or less, typically 20% or less, and more typically 10% or less.

[0075] The conversion rate of a curable composition refers to the percentage of resin converted into polymer. The conversion rate is determined by differential scanning calorimetry (DSC) using known instruments and methods on a sample of the curable composition. A sample of the curable composition can undergo a desired heating profile using DSC, and the conversion rate of the curable composition can be determined at a selected point along the heating profile. According to the method of the present invention, T m Alternatively, the conversion rate of the curable composition in T1 must be 30% or less, typically 20% or less, and more typically 10% or less.

[0076] Advantageously, the curable composition can be used in sutures. m While heating to a higher temperature T1, T m Alternatively, it has been discovered that if the conversion rate of the curable composition in T1 is 30% or less, it becomes possible to manufacture composite material parts that exhibit remarkable resistance to the formation of microcracks. Although we do not wish to be bound by theory, it is thought that at a conversion rate of 30% or less, the matrix resin is neither sufficiently viscous nor rigid to maintain the shape of the suture. Therefore, upon melting, the suture can interdiffuse with the matrix resin (as will be explained below). The manifestation of this effect is a significant reduction in microcracks in the final composite material article.

[0077] Typically, heating a composition to a temperature T1 can be achieved by any method known to those skilled in the art. In one embodiment, heating a curable composition to a temperature T1 includes heating the curable composition at a heating rate of about 10°C / min or less. In another embodiment, heating a curable composition to a temperature T1 includes heating the curable composition at a heating rate of 0.2 to 10°C / min, typically 0.5 to 2°C / min.

[0078] Melting temperature T of sutures m Any temperature T1 higher than the ambient temperature is suitable for the method to be performed. However, in one embodiment, temperature T1 is the curing temperature of the curable composition. The curing 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 supplied at a specific injection temperature that is typically higher than the ambient temperature, i.e., higher than 25°C. Thus, in some embodiments, the curable composition is supplied at the injection temperature, and T1 is the injection temperature and the T of the suture. m Higher than both of them.

[0079] In step c) of the method, the temperature T1 is maintained or heated to a temperature T2 for a sufficient time for the curable composition to cure, thereby producing a composite material article.

[0080] During the curing process, the matrix resin forms crosslinks throughout the curable composition, and the resin is considered to be a gel. Once gelled, the matrix resin no longer flows and instead behaves as a solid. The temperature at which gelation occurs is the gelation temperature T. gel The T of a specific composition gel This is typically determined by performing dynamic rheological measurements on a sample of the curable composition using known methods. Typically, a temperature sweep is applied up to 300°C at different frequencies (1, 3, 5, and 10 Hz). At a particular temperature, the tanδ (= G'' / G') curves at different frequencies intersect, and this is interpreted as the gel temperature of the polymer sample. In some embodiments, the T of the suture is used. m T of the curable composition gel It is lower than that.

[0081] If further heating is performed up to temperature T2, T2 may be any suitable temperature greater than T1, as long as the curing process is not impaired.

[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 manufactured according to the process described herein exhibit a reduction in microcracks compared to composite articles manufactured using the same process with sutures that do not contain thermoplastic polymers and have a linear density of 80 dtex or less, and even compared to composite articles manufactured using different processes with sutures that contain thermoplastic polymers and have a linear density of 80 dtex or less. Although we do not wish to be bound by theory, the conversion rate of the curable composition is controlled to be 30% or less while the curable composition is treated with the T of the sutures. m When heated to a temperature T1 higher than the specified temperature, a unique interaction (referred to herein as interdiffusion) is thought to occur between the matrix resin and the suture. The suture and matrix resin of the non-crimped fabric are thought to interdiffuse during the process, resulting in little to no regions having only the chemical characteristics of the suture. In other words, the suture is thought to diffuse toward the matrix resin as it melts, while the matrix resin, which has not yet gelled and does not have sufficient viscosity or stiffness to take the shape of the suture, is also thought to diffuse toward the suture. Thus, interdiffusion of the two materials occurs within the curable composition, resulting in desirable bulk properties, such as a reduction in microcracks.

[0084] Composite articles manufactured according to the methods described herein can be evaluated for microcracks using methods known to those skilled in the art. Since microcracks are generally known to occur as a result of the manufacturing process, a baseline evaluation of microcracks in composite articles is performed. For the purpose of evaluating microcracks due to thermal cycling and exposure to high humidity periods, a sample of the composite article can be placed under conditions in which it is maintained at an ambient temperature and / or humidity level for a specified time, 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 humid 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 humid heat loading conditions, microcracks may be observed in the composite article. Quantification of microcracks is usually performed using an optical microscope at the scale of each ply and fiber.

[0085] Processes comprising NCF fabric, sutures, support structures, and curable compositions used therein, as well as composite material articles produced, will be further described by the following non-limiting examples. [Examples]

[0086] Example 1. Manufacturing of NCF composite material Unless otherwise specified, the non-crimped fabrics (NCF) used herein are manufactured and supplied by CHOMARAT (France). Carbon fiber (Toho Tenax IMS65 24k E23) was used to manufacture the NCF using a Karl Mayer MAX 5 multi-axis machine. The NCF was a bi-oriented NCF with two carbon fiber layers superimposed (the first upper layer oriented at +45° and the second lower layer at -45°). The structure was Biax, and the NCF width was 125 cm. The two layers were sutured with various sutures. 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 That is the case.

[0087] A twin-screw NCF layup was impregnated with resin (EP2400PRISM®, available from Solvay) using a vacuum-assisted resin injection process and cured according to the supplier's instructions. The resin was first heated to 100°C in a vacuum oven and then degassed under vacuum for 15 minutes. Injection was performed at 100°C under a vacuum of approximately 10 mbar.

[0088] NCF composite materials were cured using two different curing profiles. In one curing profile, Profile A, the plate was heated to 180°C at a rate of 2°C / min, held at 180°C for 2 hours, and then cooled to 80°C at a rate of 0.5°C / min. In the other curing profile, Profile B, the plate was heated to 110°C at a rate of 2°C / min, held at 110°C for 12 hours, then heated again to 180°C at a rate of 2°C / min, held at 180°C for 2 hours, and then cooled to 80°C at a rate of 0.5°C / min. In Profile A, the conversion rate of the NCF composite material at 180°C was approximately 6%. In Profile B, the conversion rate of the NCF composite material up to the time of heating to 180°C was approximately 50%. The fabricated NCF composite materials are summarized in Table 1 below.

[0089] [Table 1]

[0090] Example 2. Moisture heat loading of NCF composite material An NCF composite material manufactured according to Example 1 was subjected to 2000 accelerated humid heat loads representing typical operating conditions during the lifecycle of a subsonic jet (see Figure 1). This load consisted of five blocks of 400 cycles each, with each block comprising two different loading stages: a first steady-state "water absorption" stage where the sample is exposed to 95% RH at 50°C for 12 hours, and a second thermal drying cycle stage. During this final stage, the sample was cycled 400 times at a temperature rate of 9°C / min in the temperature range of -54 to 80°C. Each cycle lasted 1 hour (4 × 15 minutes), thus logically giving each heating / cooling stage 15 minutes and each isothermal step at 80°C and -54°C 15 minutes. It took a total of approximately 3 months to reach 2000 cycles. The minimum size of the sample to be cycled was 50 × 50 mm. 2 That is the case.

[0091] Example 3. Quantification of microcracks Samples of the NCF composite material subjected to the moist heat loading procedure described in Example 2 (i.e., cycled samples) were taken every 400 cycles, i.e., after 400, 800, 1200, 1600, and 2000 cycles. After each 400 moist heat cycles (12 hours of conditioning under moist conditions followed by 400 thermal cycles). 20 × 20 × 3.2 mm 3 Microcrack analysis samples of the following size were taken from the center of the cycled sample. These analytical samples were carefully cut with a microslitter to avoid damage during cutting. Observation cross section (20 × 3.2 mm) 2 The specimens were polished using an automatic polishing machine (Struers TegraPol). For each material, the microcrack analysis step (e.g., 400 cycles) should be prepared with a single cycled specimen (one cut and three polishing steps). Therefore, a complete analysis of 2000 cycles (5 × 400 moist heat cycles) requires five specimens per material type (one sample per analysis step). The total microcrack density (density, cm³) of each composite material analyzed was calculated. -1 ) are summarized in Table 2 below.

[0092] [Table 2]

[0093] Example 4. Characterization of NCF composite material The cured NCF composite material was examined by infrared spectroscopy. The chemical composition of the polymer suture / cured epoxy resin region was determined using infrared ATR germanium spectroscopy in reflection mode. A 20 × 20 mm sample was 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 Vertex 70, and the instrument used for microscopy was a Hyperion 2000.

[0094] The compositional profile (mapping) was determined along defined pathways every 10–30 μm within the sample region. Samples 3 and 5 were analyzed. The target IR band was the band corresponding to the polyamide in the suture, i.e., 1637 cm². -1 C=O band (band 1, C=O stretch), 1550cm -1 NH (band 2, NH deformation and CN stretching), and the harmonics of band 2 at 1550 cm⁻¹, namely 3082 and 3086 cm⁻¹. -1 It was 1237 cm² for epoxy resin. -1 The focus was on the symmetric coupling vibrations of CO and CC in the epoxy cycle.

[0095] In Sample 5, it was observed that the melting of the suture did not cause the loss of the suture filament shape. In the suture filament region, the infrared spectrum showed vibrational bands attributable to the polyamide, suggesting that the chemical composition of this region is that of the suture. In the epoxy region, the infrared spectrum showed vibrational bands attributable 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 filaments appears to have disappeared due to the melting of the suture. Regardless of whether the suture filament region or the epoxy region was selected, the infrared spectrum showed both vibrational bands attributable to the polyamide and vibrational bands attributable to the epoxy resin. This suggests 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. A method for manufacturing articles made of composite materials, a) To provide a curable composition comprising a matrix resin and a non-crimped fabric, wherein the non-crimped fabric comprises at least one layer of unidirectionally oriented multifilament carbon yarns and multifilament sutures connecting the multifilament carbon yarns, and the sutures contain a thermoplastic polymer and have a linear density of 80 dtex or less; b) The curable composition is heated to a temperature T １ Heating to a certain temperature, and heating the curable composition to the temperature T1 includes heating the curable composition at a heating rate of about 10°C / min or less, T １ The melting temperature of the suture (T ｍ ) is higher than T measured by differential scanning calorimetry. ｍ or T １ The conversion rate of the matrix resin in the above-mentioned region is 30% or less; c) A sufficient time and temperature T for the curable composition to cure. １ Maintain or temperature T ２ To heat to a certain extent, thereby manufacturing composite material articles, A method that includes this.

2. The method according to claim 1, wherein the time required for the curable composition to cure is 6 hours or less.

3. The method according to claim 1 or 2, wherein the suture has a melting temperature of 230°C or lower.

4. The method according to claim 1 or 2, wherein the melting temperature of the suture is 70°C to 200°C.

5. The method according to claim 1 or 2, wherein the suture includes one or more thermoplastic fibers or filaments.

6. The method according to claim 1 or 2, wherein the thermoplastic polymer of the suture is a polymer selected from the group consisting of polyester, polyamide, polyimide, polycarbonate, polyurethane, and copolymers thereof.

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

8. The method according to 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 according to claim 1 or 2, wherein the non-crimped fabric further comprises a veil.

10. The curable composition is heated to the temperature T. １ The method according to claim 1 or 2, wherein heating to a certain extent includes heating the curable composition at a heating rate of 0.2 to 10°C / min.

11. heating the curable composition to the temperature T １ The method according to claim 1 or 2, comprising heating the curable composition at a heating rate of 0.5 to 2 °C / min until the temperature reaches T.

12. The temperature T １ The method according to claim 1 or 2, wherein is the curing temperature of the curable composition.

13. The T of the suture thread ｍ However, the temperature at which the curable composition gels (T ｇｅｌ The method according to claim 1 or 2, wherein the result is lower than )

14. The curable composition is supplied at the injection temperature, T １ The injection temperature and the T of the suture ｍ The method according to claim 1 or 2, which is higher than both of the above.

15. The method according to claim 1 or 2, wherein the thermoplastic polymer of the suture is a semicrystalline polymer.

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

17. The method according to claim 1 or 2, wherein the suture thread and the matrix resin of the non-crimped fabric mutually diffuse in the method, and as a result, there are almost no regions that have only the chemical properties of the suture thread.

18. The method according to claim 1 or 2, wherein the manufactured composite material article exhibits a reduction in microcracks compared to a composite material article manufactured using sutures that do not contain a thermoplastic polymer and have a linear density of 80 dtex or less.

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