Laminate

Abstract

To provide an FRP laminate capable of suppressing intra-layer transition to unidirectional reinforcing fiber by allowing crack propagation on a reinforcing fiber fabric side, in the FRP laminate formed by combining a unidirectional reinforcing fiber layer and a reinforcing fiber fabric layer.SOLUTION: There is provided a laminate including: a layer of a fiber-reinforced composite material containing unidirectionally aligned reinforcing fiber and a matrix resin (hereinafter referred to as a unidirectional reinforcing fiber layer); and a layer of a fiber-reinforced composite material containing a reinforcing fiber fabric and a matrix resin laminated adjacent to its surface (hereinafter referred to as a reinforcing fiber fabric layer), wherein a resin layer exists between the unidirectional reinforcing fiber of at least one unidirectional reinforcing fiber layer and the reinforcing fiber fabric of at least one reinforcing fiber fabric layer adjacent to a surface thereof, the resin layer containing spherical polymer particles and amorphous polymer particles, and in a cross-section perpendicular to a fiber direction of the unidirectional reinforcing fiber, a presence ratio of the amorphous polymer particles in an area occupied by the polymer particles present on the reinforcing fiber fabric side of the resin layer is higher than 50%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a laminate comprising a layer of fiber-reinforced composite material containing reinforcing fibers aligned in one direction, and a layer of fiber-reinforced composite material containing a reinforcing fiber fabric laminated on its surface. [Background technology]

[0002] In recent years, fiber-reinforced composite materials (FRPs) using carbon fibers and aramid fibers as reinforcing fibers have been utilized in structural materials for aircraft and automobiles, sports equipment such as tennis rackets, golf shafts and fishing rods, and general industrial applications, taking advantage of their high specific strength and specific modulus.

[0003] The manufacturing methods for FRP include using a prepreg, which is a sheet-like intermediate material in which reinforcing fibers are impregnated with uncured matrix resin, and curing it, or the resin transfer molding method, in which liquid resin is poured into reinforcing fibers placed in a mold and then cured. Of these manufacturing methods, the method using prepregs usually involves laminating multiple prepregs and then heating and pressurizing them to obtain an FRP molded product.

[0004] In particular, for structural applications such as aircraft and automobiles, FRP containing a layer of FRP with reinforcing fibers aligned in one direction and a matrix resin (hereinafter referred to as a unidirectional reinforcing fiber layer or unidirectional FRP) is sometimes manufactured, and then perforated for purposes such as joining with other molded products. In this case, if the reinforcing fibers on the surface of the FRP are aligned in one direction, there is a problem that the reinforcing fibers that are cut during processing will peel off, become frayed, and have a poor appearance.

[0005] To address this problem, it is known that laminating a layer of FRP containing reinforcing fiber fabric and matrix resin (hereinafter referred to as the reinforcing fiber fabric layer or woven FRP) onto the surface of the unidirectional FRP makes it less prone to splintering compared to when the fibers are aligned in one direction. Therefore, when manufacturing FRP that requires drilling, woven FRP is often used on the surface (Patent Document 1).

[0006] One method for suppressing delamination is to form a resin layer between the layers and arrange polymer particles within the resin layer. It has been reported that in FRP consisting only of unidirectional reinforcing fibers, arranging polymer particles between the layers increases energy absorption during crack propagation between layers, thereby achieving high interlaminar toughness (Patent Documents 2-4). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2005-126557 [Patent Document 2] Special Publication No. 2010-505990 [Patent Document 3] Japanese Patent Publication No. 2018-24879 [Patent Document 4] Special Publication No. 2017-505844 [Overview of the project] [Problems that the invention aims to solve]

[0008] In the invention described in Patent Document 1, in an FRP made by combining a reinforced fiber fabric and unidirectional reinforcing fibers, residual stress is generated between the fabric FRP and the unidirectional FRP at room temperature because there is a difference in the coefficient of linear expansion of the two in the non-fiber direction of the unidirectional reinforcing fibers. Furthermore, because there is a difference in elastic modulus, delamination (hereinafter referred to as interlaminar delamination) tended to occur between the reinforced fiber fabric layer and the unidirectional reinforcing fiber layer during drilling.

[0009] In the inventions described in Patent Documents 2 to 4, when cracks propagate between layers, the cracks transition from the interlaminar layer to the fiber layer (hereinafter referred to as intralaminar transition), preventing energy absorption by polymer particles and resulting in lower interlaminar toughness than expected. In particular, in the interlaminar layers of an FRP laminate combining a unidirectional reinforced fiber layer and a reinforced fiber woven fabric layer, intralaminar transition does not occur on the reinforced fiber woven fabric side because the fibers are constrained by each other, but intralaminar transition to the unidirectional reinforced fibers was a problem.

[0010] The object of the present invention is to provide an FRP laminate comprising a unidirectional reinforcing fiber layer and a reinforcing fiber fabric layer, in which intralayer transition to unidirectional reinforcing fibers can be suppressed by allowing crack propagation on the reinforcing fiber fabric side. [Means for solving the problem]

[0011] A layer of fiber-reinforced composite material containing reinforcing fibers aligned in one direction and a matrix resin (hereinafter referred to as the unidirectional reinforcing fiber layer), A laminate comprising a layer of fiber-reinforced composite material (hereinafter referred to as the reinforcing fiber fabric layer) containing a reinforcing fiber fabric and a matrix resin, which are laminated adjacent to the surface, A resin layer exists between the unidirectional reinforcing fibers in at least one unidirectional reinforcing fiber layer and the reinforcing fiber fabric in at least one reinforcing fiber fabric layer adjacent to its surface. The resin layer contains spherical polymer particles and amorphous polymer particles. The laminate is such that, in a cross-section perpendicular to the fiber direction of the unidirectional reinforcing fibers, the proportion of amorphous polymer particles in the area occupied by polymer particles on the reinforcing fiber fabric side of the resin layer is higher than 50%. [Effects of the Invention]

[0012] According to the present invention, by allowing crack propagation in the resin layer on the reinforcing fiber fabric side between the unidirectional reinforcing fibers and the reinforcing fiber fabric, it is possible to provide an FRP that is less prone to delamination. [Modes for carrying out the invention]

[0013] The present invention will be described in more detail below.

[0014] The FRP laminate of the present invention is typically formed by laminating a prepreg consisting of a reinforcing fiber fabric and a matrix resin onto the surface of a prepreg consisting of reinforcing fibers aligned in one direction and a matrix resin, and then curing the laminate. Furthermore, a resin layer is formed between the unidirectional reinforcing fibers and the reinforcing fiber fabric, and both amorphous polymer particles and spherical polymer particles are arranged in this resin layer. Moreover, in the resin layer, at least in a cross-section perpendicular to the fiber direction of the unidirectional reinforcing fibers, the proportion of amorphous polymer particles in the area occupied by particles on the reinforcing fiber fabric side of the resin layer is high. <Material> (Reinforced fiber) Unidirectional reinforcing fibers are generally used as reinforcing fiber bundles, which are bundles of many single fibers. For example, with carbon fibers, a bundle of approximately 1,000 to 1,000,000 single fibers is usually called a "tow," and a sheet-like reinforcing fiber bundle can be obtained by arranging these tows. When the fibers are arranged in one direction along the longitudinal direction, it is called a unidirectional reinforcing fiber, and when the fibers are arranged in a combination of longitudinal and transverse directions, it is called a reinforcing fiber fabric. When prioritizing the mechanical properties of FRP, unidirectional materials are used, while reinforcing fiber fabrics tend to be used when suppressing burrs during drilling or when creating composite shapes. Examples of reinforcing fiber fabrics include plain weave, twill weave, and satin, and other materials such as knitted fabrics and braided fabrics can also be used. The reinforcing fibers used in this invention include carbon fibers, glass fibers, aramid fibers, boron fibers, PBO fibers, high-strength polyethylene fibers, alumina fibers, and silicon carbide fibers. Two or more of these fibers may be mixed and used. In particular, carbon fibers can be suitably used in applications where there is a high demand for lightweight and high-strength materials due to their excellent specific modulus of elasticity and specific strength.

[0015] Examples of commercially available carbon fibers for unidirectional reinforcing fibers include "Torayca (registered trademark)" T800G-24K, "Torayca (registered trademark)" T800S-24K, "Torayca (registered trademark)" T700G-24K, "Torayca (registered trademark)" T300-3K, and "Torayca (registered trademark)" T700S-12K (all manufactured by Toray Industries, Inc.).

[0016] Examples of commercially available carbon fibers for reinforcing fiber fabrics include "Torayca (registered trademark)" Cross CM6644G. (Matrix resin) The matrix resin is a thermosetting resin composition, and its type is not particularly limited. Any thermosetting resin composition mainly composed of epoxy resin, phenolic resin, unsaturated vinyl ester resin, unsaturated polyester resin, bismaleimide resin, bismaleimide triazine resin, cyanate ester resin, benzoxazine resin, etc. can be preferably used.

[0017] In particular, epoxy resin has good adhesion to reinforcing fibers, so it can be particularly preferably used when obtaining FRP with excellent strength. Among them, trifunctional or higher epoxy resins are preferably used. The trifunctional or higher epoxy resin used in the present invention is a compound having three or more epoxy groups in one molecule. Examples of trifunctional or higher epoxy resins include glycidylamine type epoxy resins and glycidyl ether type epoxy resins.

[0018] Using a trifunctional or higher epoxy resin is more preferable because it improves the interlaminar toughness of the laminate and the elastic modulus of the matrix resin. Furthermore, if the elastic modulus of the matrix resin around amorphous polymer particles is even higher than that of the particles, stress concentration in the resin around the amorphous polymer particles increases further, making it easier for cracks to propagate on the reinforcing fiber fabric side and suppressing intralayer transition to unidirectional reinforcing fibers, which is even more preferable. In a trifunctional or higher epoxy resin, the number of functional groups is preferably 3 to 7, and more preferably 3 to 4. If the number of functional groups is too high, the matrix resin after curing may become brittle, impairing the interlaminar toughness. Examples of epoxy resins include diaminodiphenylmethane type, diaminodiphenylsulfone type, aminophenol type, metaxylenediamine type, 1,3-bisaminomethylcyclohexane type, and isocyanurate type. In particular, diaminodiphenylmethane type and aminophenol type epoxy resins are especially preferred due to their good balance of physical properties.

[0019] Examples of glycidylamine-type epoxy resins with three or more functions include diaminodiphenylmethane type, diaminodiphenylsulfone type, aminophenol type, metaxylenediamine type, 1,3-bisaminomethylcyclohexane type, and isocyanurate type epoxy resins. Among these, diaminodiphenylmethane type and aminophenol type epoxy resins are particularly preferred due to their good balance of physical properties. Examples of glycidyl ether-type epoxy resins with three or more functions include phenol novolac type, orthocresol novolac type, trishydroxyphenylmethane type, and tetraphenyloleethane type epoxy resins.

[0020] Commercially available aminophenol-type epoxy resins include ELM120, ELM100, and ELM434 (all manufactured by Sumitomo Chemical Co., Ltd.), “jER®” 630 (manufactured by Mitsubishi Chemical Corporation), and “Araldite®” MY0510 (manufactured by Huntsman Corporation), “Araldite®” MY0600 (manufactured by Huntsman Advanced Materials), “Araldite®” MY0610 (manufactured by Huntsman Advanced Materials), and “Araldite®” MY721 (manufactured by Huntsman Advanced Materials).

[0021] Commercially available phenol novolac type epoxy resins include DEN431 and DEN438 (both manufactured by Dow Chemical Company) and “jER®” 152 (manufactured by Mitsubishi Chemical Corporation).

[0022] Examples of commercially available orthocresol novolac type epoxy resins include EOCN-1020 (manufactured by Nippon Kayaku Co., Ltd.) and “Epiclon®” N-660 (manufactured by DIC Corporation).

[0023] Among epoxy resins other than trifunctional epoxy resins, glycidyl ether type epoxy resins with phenol as a precursor are preferably used as bifunctional epoxy resins. Examples of such epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, naphthalene type epoxy resin, biphenyl type epoxy resin, urethane-modified epoxy resin, hydantoin type and resorcinol type epoxy resins, and the like.

[0024] Commercially available bisphenol A type epoxy resins include "EPON®" 825 (manufactured by Mitsubishi Chemical Corporation), "Epiclon®" 850 (manufactured by DIC Corporation), "Epotote®" YD-128 (manufactured by Nippon Steel Chemical Corporation), and DER-331 and DER-332 (both manufactured by Dow Chemical Corporation). Examples of bisphenol F type epoxy resins include GY285 (bisphenol F, manufactured by Huntsman Advanced Materials).

[0025] The epoxy resin composition for FRP of the present invention is preferably used in combination with a curing agent. The curing agent described herein is a curing agent for the epoxy resin contained in the epoxy resin composition of the present invention, and is a compound having an active group that can react with epoxy groups. Specific examples of curing agents include dicyandiamide, aromatic polyamines, aminobenzoic acid esters, various acid anhydrides, phenol novolac resins, cresol novolac resins, polyphenol compounds, imidazole derivatives, aliphatic amines, tetramethylguanidine, thiourea adduct amines, carboxylic acid anhydrides such as methylhexahydrophthalic anhydride, carboxylic acid hydrazides, carboxylic acid amides, polymer captans, and Lewis acid complexes such as boron trifluoride ethylamine complexes.

[0026] By using aromatic polyamines as curing agents, epoxy resin cured products with good heat resistance can be obtained. In particular, among aromatic polyamines, various isomers of diaminodiphenylsulfone are the most suitable curing agents for obtaining epoxy resin cured products with good heat resistance.

[0027] Furthermore, by using a combination of dicyandiamide and a urea compound, such as 3,4-dichlorophenyl-1,1-dimethylurea, or imidazoles as a curing agent, high heat and water resistance can be obtained while curing at relatively low temperatures. Curing epoxy resin with acid anhydrides yields a cured product with lower water absorption compared to curing with amine compounds. In addition, by using latent versions of these curing agents, such as microencapsulated versions, the storage stability of the prepreg, particularly its tack and drape, is less likely to change even when left at room temperature. These curing agents may be used individually or in combination.

[0028] Commercially available aromatic polyamine curing agents include "Seika Cure®" S (manufactured by Wakayama Seika Kogyo Co., Ltd.), MDA-220 (manufactured by Mitsui Chemicals, Inc.), "jER Cure®" W (manufactured by Mitsubishi Chemical Corporation), and 3,3'-DAS (manufactured by Mitsui Chemicals, Inc.), "Lonzacure®" M-DEA (manufactured by Lonza Inc.), "Lonzacure®" M-DIPA (manufactured by Lonza Inc.), "Lonzacure®" M-MIPA (manufactured by Lonza Inc.), and "Lonzacure®" DETDA 80 (manufactured by Lonza Inc.). (Polymer Particles) In this invention, by arranging polymer particles in the resin layer, the toughness of the matrix resin is improved and the interlaminar toughness is enhanced when it is used as FRP. When polymer particles are used, stress concentration occurs in the resin around the particles when cracks propagate in the resin layer, so the cracks propagating in the resin layer propagate toward the polymer particles, and the energy required to break the resin layer becomes larger, thus providing high interlaminar toughness. The polymer particles used in this invention are preferably polymer resins that can be mixed or dissolved in the matrix resin, and among them, polyamides are most preferred, and among polyamides, nylon 6, nylon 11, nylon 12, and copolymers of nylon 6 and 12 provide particularly good adhesion strength with thermosetting resins. The shape of these polymer particles can be spherical polymer particles with a high ratio of the minor axis to the major axis (hereinafter referred to as sphericity) and amorphous polymer particles with low sphericity, and both are used in combination in this invention.

[0029] The average particle size of spherical polymer particles is preferably in the range of 5 to 50 μm, more preferably in the range of 7 to 40 μm, and even more preferably in the range of 10 to 30 μm. It may also be a combination of either the upper limit or the lower limit mentioned above. By setting the average particle size to 5 μm or more, the polymer particles can remain in the resin layer of the resulting laminate without penetrating the bundle of reinforcing fibers, and by setting the average particle size to 50 μm or less, the thickness of the resin layer on the prepreg surface can be optimized, and the fiber mass content in the resulting laminate can be optimized. The preferred range for the average particle size of amorphous polymer particles is the same as the range for the average particle size of spherical polymer particles, and the same reasons as above are considered to be the case.

[0030] Here, the average particle size of polymer particles is determined by taking photographs of both spherical and irregularly shaped particles at a magnification of 1000 times or more using a microscope such as a scanning electron microscope, randomly selecting particles, defining the particle size as the diameter of the circle circumscribing the particle, and then calculating the average particle size (n=50).

[0031] The use of the aforementioned spherical polymer particles reduces delamination during drilling of FRP. In particular, using spherical polymer particles does not degrade the flow properties of the epoxy resin, resulting in excellent impregnation into reinforcing fibers and potentially reducing interlaminar transitions during drilling of FRP. By using polymer particles with high sphericity, stress concentration in the resin around the polymer particles is reduced when cracks propagate through the resin layer, thereby achieving high interlaminar toughness. The sphericity of the spherical polymer particles is in the range of 90 to 100, preferably 95 or higher, and more preferably 97 or higher. Examples of commercially available spherical polymer particles include "Amiran®" SP-500, SP-10, TR-1, and TR-2 (manufactured by Toray Industries, Inc.). Furthermore, examples of spherical polymer particles made of polyamide include polyamide particles described in International Publication No. 2018 / 207728 (explained in the examples).

[0032] Here, the sphericity of the polymer particles is calculated by observing the individual particle diameters at 1000x magnification using a scanning electron microscope, selecting 30 arbitrary particles from the photographs, measuring their short and long axes, and then calculating the sphericity according to the following formula.

[0033]

number

[0034] The preferred weight ratio of spherical polymer particles added to the total epoxy resin is 3% to 20% by mass. A ratio of 3% or more by mass allows for high interlaminar toughness, while a ratio of 20% or less by mass allows for a lower viscosity resin, resulting in a uniform film.

[0035] Regarding the amorphous polymer particles, while spherical polymer particles have a uniform shape, amorphous polymers have low sphericity and an irregular shape. Therefore, when cracks propagate in the resin layer, the stress concentration in the resin around the particles differs depending on the particle shape, and the fracture of the resin around the particles occurs irregularly, which can induce crack deflection. The sphericity of amorphous polymer particles that can induce crack deflection is preferably in the range of 30 to 80. If the sphericity is too low, the stress concentration in the resin around the particles becomes too high, fracture occurs prematurely, and the resulting interlaminar toughness may be low.

[0036] Examples of commercially available amorphous polymer particles include "Orgasol®" 1002D, 2001UD, 2001EXD, 2002D, 3202D, 3501D, 3502D (all manufactured by Arkema).

[0037] The preferred weight ratio of amorphous polymer particles added to the total epoxy resin is 3% to 20% by mass. A ratio of 3% or more by mass allows for frequent crack bending, while a ratio of 20% or less by mass allows for a lower viscosity resin, resulting in a uniform film.

[0038] Furthermore, by increasing the proportion of amorphous polymer particles in the area occupied by particles on the reinforcing fiber fabric side of the resin layer to more than 50% in a cross-section perpendicular to the fiber direction of the unidirectional reinforcing fibers, it becomes possible to divert cracks propagating within the resin layer towards the reinforcing fiber fabric side. This makes it possible to suppress intralayer transition to the unidirectional reinforcing fibers. The measurement method for the above proportion will be detailed in the examples described later. The reinforcing fiber fabric side of the resin layer refers to the area of ​​the resin layer closer to the reinforcing fiber fabric in the resin layer located between the unidirectional reinforcing fibers and the reinforcing fiber fabric. Specifically, five locations arbitrarily selected from the above cross-section are imaged, and the center line of the resin layer is obtained from the imaged screen using the method described later in the examples. The area on the reinforcing fiber fabric side of the center line is defined as the "area of ​​the resin layer closer to the reinforcing fiber fabric," and the area ratio P of polymer particles and the area ratio I of amorphous polymer particles in relation to the area of ​​this region are measured, and I is obtained by dividing by P. Polymer particles located on the center line are not measured. Similarly, the above prevalence ratio is calculated for the five cross-sectional images, and the average value is taken.

[0039] Here, since the fibers of the reinforcing fiber fabric are constrained by each other, intralayer transition to the reinforcing fiber fabric layer does not usually occur. The proportion of the amorphous polymer particles, which can more reliably divert cracks propagating through the resin layer towards the reinforcing fiber fabric, is preferably in the range of 60% or more. [Examples]

[0040] The laminates of the present invention will be described in more detail below with reference to examples. The resin raw materials, prepregs, and methods for producing and evaluating the FRP laminates used in the examples are shown below. Unless otherwise specified, the production environment and evaluation of the prepregs in the examples were carried out in an atmosphere of 25°C ± 2°C and 50% relative humidity. <Carbon fiber (for unidirectional reinforcement)> "Torayca (registered trademark)" T800S-24K (carbon fiber with 24,000 filaments, tensile strength of 7.0 GPa, tensile modulus of elasticity of 324 GPa, and tensile elongation of 2.0%, manufactured by Toray Industries, Inc.). <Carbon fiber (for reinforced fiber fabrics)> "Trading Card (Registered Trademark)" Cloth "CM6644G" (Manufactured by Toray Industries, Inc.). <Matrix resin> Trifunctional or higher epoxy resins • ELM434 (Tetraglycidyldiaminodiphenylmethane, manufactured by Sumitomo Chemical Co., Ltd.) • Araldite® MY721 (Tetraglycidyldiaminodiphenylmethane, manufactured by Huntsman Advanced Materials) • Araldite® MY0600 (triglycidyl meta-aminophenol, manufactured by Huntsman Advanced Materials) bifunctional epoxy resin • "EPON(registered trademark)" 825 (Bisphenol A, manufactured by Mitsubishi Chemical Corporation) • GY285 (Bisphenol F, manufactured by Huntsman Advanced Materials) <Hardening agent> • "Seika Cure (registered trademark)"-S (4,4'-diaminodiphenylsulfone, manufactured by Wakayama Seika Co., Ltd.) <Thermoplastic resin> • "Sumika Excel (registered trademark)" PES5003P (polyethersulfone, manufactured by Sumitomo Chemical Co., Ltd.). <Polymer particles> • Spherical polymer particles: Six polyamide particles obtained by the following manufacturing method (mode diameter: 15.0 μm, average particle size: 15.0 μm) Based on International Publication No. 2018 / 207728, 200g of ε-caprolactam (manufactured by Toray Industries, Inc.), 800g of polyethylene glycol (Wako Pure Chemical Industries, Ltd., Grade 1 polyethylene glycol 20,000, weight-average molecular weight 18,600) as the second polymer component, and 1,000g of water were added to a 3L autoclave equipped with a helical ribbon-type stirring blade. After forming a homogeneous solution, the autoclave was sealed and purged with nitrogen. Subsequently, the stirring speed was set to 100 rpm and the temperature was raised to 240°C. At this time, the system pressure was 10 kg / cm². 2 After reaching a certain pressure, the pressure becomes 10 kg / cm². 2The pressure of the water vapor was controlled by slightly releasing it to maintain the desired temperature. After the temperature reached 240°C, 0.2 kg / cm³ was released. 2 The pressure was released at a rate of 1 minute. Then, the temperature was maintained for 1 hour while flowing nitrogen to complete polymerization, and the slurry was discharged into a 2,000 g water bath. After dissolving the dissolved material, the slurry was filtered, and 2,000 g of water was added to the filtered product and washed at 80°C. After removing the aggregates that had passed through a 200 μm sieve, the slurry liquid was filtered again to isolate the product, and the filtered product was dried at 80°C for 12 hours to prepare 140 g of polyamide 6 powder. The melting point of the obtained powder was 218°C, the same as polyamide 6, and the crystallization temperature was 170°C. • Shapeless polymer particles "Orgasol®" 1002 D NAT1 (Arkema, Inc., average particle size: 20.0 μm) "Orgasol®" 3502 D NAT1 (Arkema, Inc., average particle size: 20.0 μm) (1) Preparation of epoxy resin composition The epoxy resin and thermoplastic resin described above were kneaded together as shown in Table 1, and the temperature was raised to 150°C or higher. The mixture was then stirred for 1 hour to dissolve the thermoplastic resin and obtain a transparent, viscous liquid. After the liquid was cooled while being kneaded, a curing agent was added and the mixture was kneaded further to obtain the first resin composition.

[0041] Furthermore, the epoxy resin and thermoplastic resin were kneaded as shown in Table 1, the temperature was raised to 150°C or higher, and the mixture was stirred for 1 hour to dissolve the thermoplastic resin and obtain a transparent, viscous liquid. After the liquid was cooled while being kneaded, spherical polymer particles and amorphous polymer particles were added and kneaded as shown in Table 1, and then a curing agent was added and kneaded to obtain a second resin composition. (2) Manufacturing of unidirectional prepregs The first resin composition or the second resin composition prepared in (1) above was uniformly applied to a release paper coated with silicone, and the first resin film (resin basis weight 30 g / m²) was formed. 2 ), second resin film (resin basis weight 20g / m²) 2) was performed. Carbon fibers uniformly aligned in one direction were sandwiched between two first resin films, and the process was heated and pressurized using a press roll to obtain a primary prepreg in which the carbon fibers were impregnated with the first resin composition. Next, both release papers were peeled off from the primary prepreg. Then, the primary prepreg was sandwiched between two second resin films, and the process was heated and pressurized using a press roll to obtain a unidirectional prepreg in which the primary prepreg was impregnated with the second resin composition (carbon fiber mass 190 g / m²). 2 , resin content 35.5% by mass). (3) Manufacturing of textile prepregs The materials were prepared using a two-stage impregnation method. The first or second resin composition prepared in (1) above was uniformly applied to a release paper coated with silicone to form the first resin film and the second resin film, respectively. A carbon fiber fabric was sandwiched between the two first resin films and heated and pressed using a press roll to obtain a primary prepreg in which the carbon fibers were impregnated with the first resin composition. Next, both release papers were peeled off from the primary prepreg. Then, the primary prepreg was sandwiched between two second resin films and heated and pressed using a press roll to obtain a fabric prepreg in which the primary prepreg was impregnated with the second resin composition (carbon fiber mass 195 g / m²). 2 , resin content 40% by mass). (4) Mode I interlaminar toughness (G IC ) Measurement of intralayer transition rates in the test In accordance with ASTM D5528 (2002), the intralayer transition rate was measured by the following procedures (a) to (e). (a) After cutting the unidirectional prepreg and the woven prepreg into 250 mm × 250 mm pieces respectively, the fiber directions of the unidirectional prepregs were aligned in the same direction, and two 13-ply unidirectional prepreg laminates were fabricated. With 1 ply of the woven prepreg at the center, they were laminated so as to be sandwiched between two 13-ply unidirectional prepregs, and a 27-ply prepreg laminate was fabricated by combining the unidirectional prepreg and the woven prepreg. Note that they were laminated such that the warp of the woven prepreg and the fiber direction of the unidirectional prepreg were in the same direction. To this, a rectangular fluororesin film with a thickness of 12.5 μm was inserted 40 mm from the end of the laminate in the 0° direction between one of the unidirectional prepreg and the woven prepreg (between the 13th ply and the 14th ply) to create an initial crack. (b) The laminated prepregs were covered with a nylon film without gaps, and after heating up to 180 °C at a heating rate of 1.5 °C / min in an autoclave, 2 they were heated and pressed at a temperature of 180 °C and a pressure of 7 kg / cm for 2 hours to be cured and FRP was molded. (c) With the 0° of the unidirectional material of the FRP obtained in (b) as the length direction, it was cut into a width of 25 mm and a length of 200 mm. The fiber direction was cut so as to be parallel to the length direction of the sample. (d) According to ASTM D5528 (2002), a pin load block (length 25 mm, made of aluminum) was adhered to the surface of the test piece. (e) To make it easier to observe crack propagation, white paint was applied to both side surfaces of the test piece.

[0042] Using the fabricated FRP, the intralayer transition rate was measured according to the following procedure. The test was performed using the “Instron®” 5565 model in accordance with ASTM D5528 (2002). (4)(a) Crack propagation was carried out at a crosshead speed of 1.0 mm / min from the tip of the fluororesin film inserted into the laminate in the 0° direction until the length of crack propagation reached 50 mm. After the test was completed, the crack was allowed to propagate to the edge of the test specimen, and the rate of intralayer transition within the 50 mm x test specimen width (25 mm) range from the tip of the film was measured using two test specimens according to the following formula. Using a scanning electron microscope (JEOL Ltd. scanning electron microscope JSM-6301NF), the region where the surface of the reinforcing fibers was exposed on the fracture surfaces above and below the crack propagation region was defined as the intralayer transition region. Five test specimens were measured.

[0043]

number

[0044] (5) The proportion of amorphous polymer particles in the area occupied by polymer particles on the reinforcing fiber fabric side of the resin layer The proportion of the above amorphous polymer particles in the resin layer between the unidirectional FRP and the woven FRP is (4) Mode I interlaminar toughness (G IC The portion of the test specimen without the film inserted was cut perpendicular to the fiber direction of the unidirectional reinforcing fibers. After polishing the cross-section, it was magnified 200 times with an optical microscope, and measurements were taken from images taken with the resin layer between the unidirectional reinforcing fibers and the reinforcing fiber fabric within the field of view.

[0045] In the captured image of the resin layer, the midpoint between the center of the unidirectional reinforcing fiber closest to the resin layer and the center of the reinforcing fiber fabric closest to the resin layer was obtained on an arbitrary line parallel to the out-of-plane direction. This operation was performed every 10 μm in the in-plane direction of the unidirectional reinforcing fibers in the image, and the center line of the resin layer was obtained by connecting adjacent points. In the region of the resin layer closer to the reinforcing fiber fabric than the center line of the resin layer, the area ratio P of polymer particles and the area ratio I of amorphous polymer particles were measured relative to the area of ​​that region. Polymer particles located on the center line were not measured. The proportion of amorphous polymer particles in the area occupied by polymer particles was calculated by dividing I by P. Cross-sectional images were measured at five locations, the above proportion was calculated for each, and the average value was taken. (6) Measurement of the sphericity of polymer particles The individual particle size of the polymer particles was measured by observing the particles at 1000x magnification using a scanning electron microscope (JEOL Ltd. JSM-6301NF). Thirty particles were randomly selected from the photographs, their minor and major axes were measured, and their sphericity was calculated according to the formula described above. For amorphous polymer particles, a mixture of the two types of "Orgasol®" described above in a 1:1 (mass ratio) was measured. (Example 1, Comparative Example 1) Unidirectional prepregs and reinforced fiber woven prepregs are prepared as described in (2) or (3) above, with the compositions listed in Table 1, and a prepreg laminate is constructed as described in (4)(a), and the above-mentioned (4) Mode I interlaminar toughness (G IC Test specimens were prepared and the intralayer transition rate was measured. In addition, the proportion of amorphous polymer particles in the area occupied by polymer particles on the reinforcing fiber fabric side (indicated as "Proportion of amorphous polymer particles" in the table) was measured according to (5), and the sphericity of the polymer particles was measured according to (6). The intralayer transition rate, the proportion of amorphous polymer particles, and the sphericity of the polymer particles are shown in Table 1.

[0046] [Table 1]

[0047] A comparison of Example 1 and Comparative Example 1 showed that by using amorphous polymer particles in addition to spherical polymer particles, and further increasing the proportion of amorphous polymer particles in the resin layer between the unidirectional FRP and the woven FRP in the area occupied by particles on the reinforcing fiber woven side, intralayer transition to the unidirectional reinforcing fibers was suppressed. [Industrial applicability]

[0048] According to the present invention, intralayer transition to unidirectional reinforcing fibers can be suppressed, making it suitable for use in structures subjected to drilling. For example, in aerospace applications, it is suitable for primary structural materials of aircraft such as main wings, tail wings, and floor beams; secondary structural materials such as flaps, ailerons, cowlings, fairings, and interior materials; and rocket motor cases and satellite structural materials. In general industrial applications, it is suitable for structural materials of moving objects such as automobiles, ships, and railway vehicles, as well as drive shafts.

Claims

1. A layer of fiber-reinforced composite material (hereinafter referred to as the unidirectional reinforced fiber layer) is formed by curing a prepreg consisting of reinforcing fibers aligned in one direction and a matrix resin, A laminate comprising a layer of fiber-reinforced composite material (hereinafter referred to as the reinforcing fiber fabric layer) containing a reinforcing fiber fabric and a matrix resin, which is laminated adjacent to its surface, A resin layer exists between the unidirectional reinforcing fibers in at least one unidirectional reinforcing fiber layer and the reinforcing fiber fabric in at least one reinforcing fiber fabric layer adjacent to its surface. The resin layer contains spherical polymer particles and amorphous polymer particles, the average particle size of the spherical polymer particles and amorphous polymer particles is in the range of 5 to 50 μm, and the sphericity of the amorphous polymer particles is in the range of 30 to 80. A laminate in which, in a cross-section perpendicular to the fiber direction of the unidirectional reinforcing fibers, the proportion of amorphous polymer particles in the area occupied by polymer particles on the reinforcing fiber fabric side of the resin layer is greater than 50%.

2. The laminate according to claim 1, wherein the spherical polymer particles and the amorphous polymer particles are made of polyamide.

3. The laminate according to claim 1 or 2, wherein the sphericity of the spherical polymer particles is in the range of 90 to 100.

4. The laminate according to any one of claims 1 to 3, wherein the proportion of amorphous polymer particles is in the range of 60% or more.

5. The laminate according to any one of claims 1 to 4, wherein the matrix resin contains a trifunctional or more glycidylamine-type epoxy resin.

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