Laminate and method for producing the same, fiber-reinforced composite material, aircraft member, and aircraft

Abstract

To achieve both high toughness and high elastic modulus of an interlayer resin in order to balance high impact resistance and high compressive strength in a fiber-reinforced composite material.SOLUTION: A laminate comprises: a first layer in which inorganic porous particles are dispersed in a resin composition containing a thermosetting resin (hereinafter referred to as a thermosetting resin composition); and a second layer containing reinforcing fibers and the thermosetting resin composition, wherein the mass ratio of the inorganic porous particles to the composition filling the inside of the layer (hereinafter referred to as the mass ratio of the inorganic porous particles) is smaller than that of the first layer. The laminate has a laminated structure with the first layer sandwiched between two second layers.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fiber-reinforced composite material having excellent impact resistance and compressive strength, and a laminate that is its precursor. [Background technology]

[0002] In recent years, fiber-reinforced composites (FRPs), which use reinforcing fibers such as carbon fiber and aramid fiber, have been used in a variety of applications, including structural materials for aircraft and automobiles, sports equipment such as tennis rackets, golf shafts, and fishing rods, and general industrial applications, due to their high specific strength and specific modulus. In particular, structural materials for aircraft require high impact resistance in addition to high specific strength and specific modulus. FRPs are often produced using a precursor, a laminate of a sheet substrate containing fiber and resin called a prepreg, which is then heated and cured while being molded if the resin is a thermosetting resin. When FRPs with such a laminated structure are subjected to an out-of-plane impact load, delamination can occur, reducing the compressive resistance of the structure.

[0003] As a method for improving impact resistance, Patent Document 1 cites a method of placing a resin containing thermoplastic particles between layers. By placing a resin containing thermoplastic particles between layers, the toughness between the layers is increased, and delamination between layers during impact loads is suppressed. Furthermore, Patent Document 2 describes laminating prepregs in which inorganic particles are added to resin, and curing the laminate to obtain FRP, which achieves high compressive strength. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-169541 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-149237 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the technique described in Patent Document 1 has the problem that, depending on the type of particles, the elastic modulus may be lower than that of the cured product of the thermosetting resin, resulting in a low interlayer elastic modulus. If the interlayer elastic modulus is low, the reinforcing fibers may be prone to buckling when a compressive load acts in the fiber direction of the FRP, which may reduce the compressive strength of the FRP.

[0006] Furthermore, in the method described in Patent Document 2, the inorganic particles are considered to be non-porous, not porous. In this case, when an impact load is applied to the FRP, peeling can occur between the inorganic particles and the resin, which can make it difficult to increase the toughness of the resin present between one fiber layer and an adjacent fiber layer, posing a problem that the impact resistance of the FRP cannot be increased as intended.

[0007] When FRP is molded from a laminate, in order to achieve high impact resistance, it is necessary to suppress delamination of the FRP, so it is necessary to improve the toughness of the resin between the layers. Also, in order to achieve high compressive strength of FRP, it is necessary to suppress buckling of the reinforcing fibers when a compressive load is applied in the fiber direction, so it is necessary to improve the elastic modulus of the resin between the layers.

[0008] Therefore, an object of the present invention is to achieve both high toughness and high elastic modulus for the resin between layers in order to achieve both high impact resistance and high compressive strength for FRP. [Means for solving the problem]

[0009] 1. A first layer in which inorganic porous particles are dispersed in a resin composition containing a thermosetting resin (hereinafter referred to as a thermosetting resin composition); a second layer containing reinforcing fibers and a thermosetting resin composition, the second layer having a mass ratio of inorganic porous particles to the composition filling the layer (hereinafter referred to as the mass ratio of inorganic porous particles) smaller than that of the first layer; A laminate comprising a stacked configuration in which a first layer is sandwiched between two second layers. 2. The laminate according to 1 above, wherein the thermosetting resin contained in the thermosetting resin composition is an epoxy resin. 3. The laminate according to 1 or 2 above, wherein the thermosetting resin composition contains a thermoplastic resin. 4. The laminate according to any one of the above 1 to 3, wherein the inorganic porous particles are silica particles. 5. The laminate according to any one of the above 1 to 4, wherein the inorganic porous particles have an average particle size of 1 μm or more and 100 μm or less. 6. The laminate according to any one of 1 to 5 above, wherein the pores of the inorganic porous particles are impregnated with a thermosetting resin. 7. The laminate according to any one of the above 1 to 6, wherein the reinforcing fibers are carbon fibers. 8. The laminate according to any one of 1 to 7 above, wherein the mass ratio of the inorganic porous particles in the first layer is 10 times or more the mass ratio of the inorganic porous particles in the second layer. 9. A first prepreg is prepared by impregnating a reinforcing fiber with a thermosetting resin composition, and at least one side of the first prepreg is coated with A resin film containing a thermosetting resin composition and inorganic porous particles is attached to prepare a second prepreg; A method for manufacturing laminates in which the surface of a secondary prepreg with a resin film attached is stacked in contact with one side of another primary or secondary prepreg. 10. Prepreg is prepared by impregnating the reinforcing fiber with the thermosetting resin composition; A method for producing a laminate, comprising inserting a resin film containing a thermosetting resin composition and inorganic porous particles between at least one pair of prepregs in the process of forming the laminate by stacking prepregs. 11. Prepreg is prepared by impregnating reinforcing fibers with a thermosetting resin composition; A method for manufacturing a laminate, comprising scattering inorganic porous particles between at least one pair of prepregs in the process of forming the laminate by stacking prepregs. 12. A fiber-reinforced composite material obtained by curing the laminate according to any one of 1 to 9 above. 13. An aircraft component comprising the fiber-reinforced composite material described in 12 above. 14. An aircraft comprising the component described in 13 above. [Effects of the Invention]

[0010] The laminate of the present invention can achieve both high toughness and high elastic modulus of the resin between the layers in the FRP obtained upon curing, and can therefore exhibit both high impact resistance and high compressive strength. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic cross-sectional view showing the structure of a laminate of the present invention. [Figure 2] FIG. 10 is a schematic cross-sectional view showing a method for determining the boundary between the first layer and the second layer when there is a disturbance in the fiber orientation. [Figure 3] FIG. 2 is a schematic cross-sectional view showing a laminate having a third layer in addition to a first layer and a second layer. DETAILED DESCRIPTION OF THE INVENTION

[0012] The laminate and its manufacturing method of the present invention will be described below with reference to the drawings as appropriate, but the present invention is not limited to the specific embodiments shown in the drawings, and the description of the specific embodiments shown in the drawings can also be understood as a description of the present invention as a general concept. In addition, in the present invention, a resin composition containing a thermosetting resin is called a thermosetting resin composition, and a mixture of a thermosetting resin composition and inorganic particles or organic particles including inorganic porous particles is called a thermosetting resin mixture. (Laminate) The laminate of the present invention has a first layer in which inorganic porous particles are dispersed in a thermosetting resin composition, and a second layer containing reinforcing fibers and a thermosetting resin composition, the mass ratio of inorganic porous particles to the composition filling the layer being lower than that of the first layer, and includes a laminate structure in which the first layer is sandwiched between two second layers. The above-mentioned laminate structure can also be described as a structure in which second layers are disposed on both sides of the first layer. The laminate may also consist solely of a laminate structure in which the first layer is sandwiched between two second layers.

[0013] The laminate of the present invention will be described in more detail using Figure 1. The laminate of the present invention has a first layer D in which inorganic porous particles C are dispersed in a thermosetting resin composition B. Dispersion of inorganic porous particles C in the thermosetting resin composition B improves the toughness and elastic modulus of the FRP obtained by curing compared to the thermosetting resin composition B alone. Typically, reinforcing fibers are not contained in the first layer D, but the first layer D may contain reinforcing fibers. However, it is desirable that the fiber volume content of the second layer E is higher than that of the first layer D.

[0014] The laminate of the present invention also has a second layer E containing a thermosetting resin composition B and reinforcing fibers A. By filling the spaces between the reinforcing fibers A with the thermosetting resin composition B, buckling of the reinforcing fibers A is suppressed when an in-plane compressive load is applied. Furthermore, even if a portion of the reinforcing fibers A breaks when an in-plane tensile load is applied, the surrounding fibers share the load via the thermosetting resin composition B. Therefore, when molded into an FRP, high strength is exhibited in both tension and compression.

[0015] The laminate of the present invention has a laminated structure in which two second layers E sandwich a first layer D. The presence of the first layer D, whose toughness has been improved by the inorganic porous particles C, between the two second layers E reduces interlayer delamination upon impact compared to when the interlayer is made of the thermosetting resin composition B alone. Furthermore, the improved interlayer elastic modulus makes the reinforcing fiber A contained in the second layer E less likely to buckle toward the interlayer (first layer D). Therefore, the FRP obtained by molding the laminate of the present invention can have high impact resistance and compressive strength.

[0016] The second layer E may also contain inorganic porous particles C, but the mass ratio of inorganic porous particles C to the amount of the composition filling the layer (hereinafter referred to as the mass ratio of inorganic porous particles C) is smaller than that of the first layer D. Here, the composition filling the layer refers to a mixture of a thermosetting resin composition and inorganic porous particles, i.e., a thermosetting resin mixture.

[0017] In the second layer E, since the mass ratio of the inorganic porous particles C is relatively small, the inorganic porous particles C can suppress bending of the reinforcing fibers A, and the FRP is likely to exhibit high mechanical properties. When the second layer E contains inorganic porous particles C, the mass ratio of the inorganic porous particles C in the first layer D to the second layer E is preferably 3 times or more, more preferably 5 times or more, and particularly preferably 10 times or more. The second layer E does not necessarily need to contain inorganic porous particles C.

[0018] Here, the mass ratio of inorganic porous particles C will be explained. The method for producing the laminate of the present invention will be described later. Since it is better for inorganic porous particles C to be unevenly distributed in the first layer D, it is preferable to use a resin mixture containing inorganic porous particles C for the first layer D, and to use a resin that does not contain inorganic porous particles C, or contains only a trace amount of inorganic porous particles C, for the second layer E. The mass ratio of inorganic porous particles C is <Mass ratio (%)> = <Mass of inorganic porous particles C> / (<Mass of thermosetting resin composition B> + <Mass of inorganic porous particles C>) × 100 If the material is already a laminate or FRP and the mass ratio of inorganic porous particles C in each layer is unknown, it can be estimated from the cross section as follows.

[0019] First, in the case of an uncured laminate, the thermosetting resin composition is heated and cured using an oven or autoclave until the laminate is hard enough to be cut. To achieve a cuttable hardness, the thermosetting resin composition is preferably heated and cured until its glass transition temperature reaches room temperature or higher, preferably at room temperature +50°C or higher. To prevent leakage of the thermosetting resin mixture from the laminate, it is preferable to reduce the pressure or surround the sides of the laminate. After cutting the cured laminate or FRP, the cross section is observed under an optical microscope at 200x magnification to determine the boundary F between the first layer D and the second layer E. The boundary F is determined by drawing a smooth curve along the outer edge of the layer formed by the reinforcing fiber A. Note that if there is a disorder in the orientation of the reinforcing fibers (G) that significantly protrudes from the group of other reinforcing fibers (A), as shown in Figure 2, the boundary F is determined excluding that fiber. Alternatively, an image may be taken of a location where the reinforcing fiber orientation is not disturbed. From an image captured with the in-plane direction of each layer of the laminate as the width direction, the area ratio of the inorganic porous particles C to the composition filling the layer in each of the first layer D and the second layer E is defined as <area ratio (%)>. <Area ratio (%)> = <Area of ​​inorganic porous particle C> / (<Area of ​​entire layer> - <Area of ​​reinforcing fiber A> - <Area of ​​reinforcing fiber G>) x 100 The area of ​​the inorganic porous particles C can be calculated as follows. When the particle shape in the captured image is circular and close to a perfect circle, the area can be calculated as the area of ​​a perfect circle circumscribing the cross section of each inorganic porous particle. If the aspect ratio of the particle shape in the captured image is large, or if there is any doubt about the area of ​​a perfect circle circumscribing the cross section, a shape similar to the particle shape, such as an ellipse, can be used, or the particle boundary can be determined and the internal area calculated. The width of the image should be sufficiently large, at least 5 mm, to minimize the impact of any uneven dispersion of the inorganic porous particles C in the thermosetting resin composition B. In the captured image, the <area ratio (%)> is calculated for an arbitrarily selected region with a width of at least 5 mm for the layer sandwiched between the upper and lower layers. The <area ratio (%)> may also be calculated for a region spanning the entire width of the captured image. If there is uneven dispersion of the inorganic porous particles C, a region where the particles are present is selected. Next, the <area ratio (%)> is calculated for regions of the same widthwise position and length in the upper and lower layers. Methods for determining the boundaries of the reinforcing fibers A and inorganic porous particles C in the first layer D and the second layer E include, but are not limited to, a method of binarizing using image software.

[0020] Assuming that the inorganic porous particles C are sufficiently dispersed in the thermosetting resin composition B, the volume ratio is substituted with the area ratio, and the area ratio (%) of each layer calculated by the above procedure from the densities of the thermosetting resin composition B and the inorganic porous particles C is used to calculate the following: <Mass ratio (%)> = (<Density of inorganic porous particles C> × <Area ratio (%)>) / (<Density of thermosetting resin composition B> × (100 - <Area ratio (%)>)) + <Density of inorganic porous particles C> × <Area ratio (%)>) × 100 The mass ratio of the inorganic porous particles C is estimated by the above formula and used as the mass ratio of the inorganic porous particles C. When the mass ratio of the inorganic porous particles C is calculated and confirmed to satisfy the requirements of the first layer D, i.e., to be greater than the mass ratio of the inorganic porous particles C in the two second layers E adjacent to each other above and below, the layer is determined to be the first layer D.

[0021] As shown in Figure 3, the laminate of the present invention may include a third layer H in addition to a first layer D and a second layer E. An example of the third layer H is a layer containing only the thermosetting resin composition B, which does not contain the reinforcing fibers A or the inorganic porous particles C. Furthermore, for the first layer D and the second layer E, the inorganic porous particles C may be uniformly distributed throughout the entire layer, but this is not necessarily required, and there may be a bias in the mass ratio of the inorganic porous particles C. From the viewpoint of suppressing delamination, it is preferable that the inorganic porous particles C are uniformly distributed throughout at least one first layer D.

[0022] The average thickness of the first layer of the laminate of the present invention is preferably in the range of 10 μm or more and 50 μm or less. If the average thickness of the first layer is greater than 50 μm, the layer thickness of the second layer E must necessarily be reduced for a given thickness of the laminate, which may reduce the volume fraction of the reinforcing fibers and reduce the compressive strength of the cured FRP. Furthermore, if the average thickness of the first layer is less than 10 μm, the first layer may not adequately absorb the impact energy when an impact is applied to the FRP, which may reduce the impact resistance of the FRP.

[0023] The laminate of the present invention can be cured to obtain FRP. The obtained FRP has high compressive strength and high impact resistance, making it suitable for use as an aircraft component. The aircraft includes not only aircraft that fly in the atmosphere, but also spacecraft such as space shuttles and rockets. (reinforced fiber) Examples of reinforcing fibers used in the laminate of the present invention include glass fibers, carbon fibers, aramid fibers, boron fibers, alumina fibers, and silicon carbide fibers. The diameter of a single reinforcing fiber is preferably 3 μm or more and 10 μm or less. If the diameter of a single reinforcing fiber is smaller than 3 μm, a large amount of inorganic porous particles contained in the first layer may flow into the second layer when the laminate is cured in an autoclave, causing the inorganic porous particles to bend the reinforcing fibers, resulting in a decrease in compressive strength. Furthermore, if the diameter of a single reinforcing fiber is larger than 10 μm, the fiber content in the FRP may be reduced, resulting in a decrease in the tensile strength of the FRP in the fiber direction.

[0024] Among these fibers, carbon fiber is preferred because it provides an FRP with excellent strength and elastic modulus under tension or compression. The form of the reinforcing fiber is not particularly limited, and examples that can be used include unidirectionally aligned long fibers, tow, woven fabric, mat, knit, braided cord, etc. (thermosetting resin) Examples of the thermosetting resin contained in the thermosetting resin composition include epoxy resins, vinyl ester resins, unsaturated polyester resins, phenolic resins, benzoxazine resins, urethane resins, urea resins, melamine resins, maleimide resins, cyanate resins, and diallyl phthalate resins. A combination of these resins may also be used. The composition may also contain a curing agent, a curing accelerator, a filler, and the like.

[0025] Among these thermosetting resins, epoxy resins are preferred because the cured product has excellent mechanical properties and heat resistance, as well as excellent toughness and elongation.

[0026] Examples of curing agents used with epoxy resins include aromatic amines such as diaminodiphenylmethane and diaminodiphenylsulfone, aliphatic amines, imidazole derivatives, dicyandiamide, tetramethylguanidine, thiourea-added amines, carboxylic acid anhydrides such as methylhexahydrophthalic anhydride, carboxylic acid hydrazides, carboxylic acid amides, polyphenol compounds, novolac resins, polymercaptans, and Lewis acid complexes such as boron trifluoride ethylamine complexes. (Inorganic porous particles) The first layer of the laminate of the present invention contains inorganic porous particles to improve the elastic modulus and toughness of the resin. The technique of adding inorganic particles to a thermosetting resin to improve the elastic modulus of the cured thermosetting resin is widely known. However, in cured thermosetting resin mixtures containing commonly used inorganic non-porous particles, peeling occurs at the interface between the inorganic non-porous particles and the cured thermosetting resin when cracks propagate through the mixture, resulting in low toughness. In contrast, cured thermosetting resin mixtures containing inorganic porous particles can have relatively high elastic modulus and toughness. When a thermosetting resin is kneaded with inorganic porous particles, the thermosetting resin can partially or entirely impregnate the pores of the particles. If the thermosetting resin impregnates the pores of the particles and then hardens, the anchor effect reduces the likelihood of peeling at the interface between the particles and the cured thermosetting resin. Furthermore, the interior of the inorganic porous particles is reinforced by the cured thermosetting resin, improving the toughness of the particles, and as a result, the toughness of the cured thermosetting resin mixture is also improved. Therefore, it is preferable that the pores of the inorganic porous particles in the first layer are impregnated with the thermosetting resin, and such impregnation into the pores can be confirmed by observing the cross section of the inorganic porous particles after curing and determining whether or not the cured thermosetting resin composition is present in the pores.

[0027] Examples of inorganic porous particle materials include silica, alumina, zirconia, titanium oxide, glass, and silicate minerals, and those having an elastic modulus at least three times higher than that of the cured product of the thermosetting resin composition are preferably used. Among these, silica is preferred because it is easy to process even when the particles are fine particles and is a readily available material.

[0028] The mass ratio of the inorganic porous particles in the first layer is preferably 3% or more, more preferably 10% or more. If the mass ratio of the inorganic porous particles in the first layer is less than 3%, the reinforcing effect of the inorganic porous particles is small. Furthermore, if the objective is to sufficiently impregnate the pores of each inorganic porous particle with the thermosetting resin composition, the mass ratio of the inorganic porous particles is preferably 40% or less. However, since it is not always easy to accurately determine the mass ratio, an area ratio of 5% or more may be considered to be a mass ratio of 3% or more, an area ratio of 15% or more may be considered to be a mass ratio of 10% or more, and an area ratio of 52% or less may be considered to be a mass ratio of 40% or less. This conversion is particularly suitable when the thermosetting resin is an epoxy resin and the inorganic porous particles are silica porous particles. That is, the area ratio of the inorganic porous particles in the cross section of the first layer is preferably 5% or more, more preferably 15% or more, and preferably 52% or less.

[0029] The average particle size of the inorganic porous particles is preferably in the range of 1 μm or more and 100 μm or less, and more preferably in the range of 5 μm or more and 40 μm or less. If the average particle size of the inorganic porous particles is larger than the above range, the large particles may disrupt the arrangement of the reinforcing fibers, which may reduce the compressive strength of the FRP. If the average particle size of the inorganic porous particles is smaller than the above range, the inorganic porous particles may pass between the fibers and flow into the second layer during curing of the laminate, which may reduce the impact resistance of the FRP. Here, the average particle size of the inorganic porous particles is determined by observing the inorganic porous particles at 2000x magnification with a laser microscope, and the diameter of the circle circumscribing the periphery of the particle in the observed image is taken as the individual particle size, and the average value of the individual particle sizes of 50 arbitrarily selected particles is used.

[0030] The inorganic porous particles are preferably uncoated. If the inorganic porous particles are coated, the thermosetting resin composition will not penetrate well into the inorganic porous particles when kneaded with the thermosetting resin composition and cured, which may reduce the toughness of the inorganic porous particles and decrease the impact resistance of the FRP.

[0031] Commercially available inorganic porous particles include "SiO2MS-2.2 2-19 μm" (COSPHERIC), "DiagNanotm C18 Porous Silica Particles, 30 μm" (CD Biopaticles), "DiagNanotm Plain Porous Silica Particles", PSP-06 (CD Biopaticles), and "Silica mesoporous SBA-15" (Merck). (thermoplastic resin) The thermosetting resin composition of the present invention may contain a thermoplastic resin. The thermoplastic resin to be kneaded is soluble in the thermosetting resin. Furthermore, using a thermoplastic resin having a polyaryl ether skeleton is preferable from the viewpoint of improving the elastic modulus without reducing the toughness of the resin. Examples of thermoplastic resins having a polyaryl ether skeleton include polysulfone, polyphenyl sulfone, polyether sulfone, polyether imide, polyphenylene ether, polyether ether ketone, and polyether ether sulfone. These thermoplastic resins having a polyaryl ether skeleton may be used alone or in combination. The amount of the thermoplastic resin in the thermosetting resin composition is preferably 1% or more and less than 50% by mass. In the present invention, the thermoplastic resin may be contained in any of the first, second, and third layers, and is preferably contained in all layers.

[0032] In particular, to obtain high toughness, the glass transition temperature (Tg) of the thermoplastic resin is preferably 150°C or higher, more preferably 170°C or higher. If the glass transition temperature of the thermoplastic resin to be blended is less than 150°C, high toughness may not be obtained. Furthermore, the terminal functional group of the thermoplastic resin is preferably a hydroxyl group, a carboxyl group, or a thiol group, and it is also preferable to use an acid anhydride. The terminal functional group of such a thermoplastic resin reacts with the epoxy resin, thereby improving the toughness of the cured product of the thermosetting resin composition. Specifically, commercially available polyethersulfone products include "Sumikaexcel (registered trademark)" PES3600P, "Sumikaexcel (registered trademark)" PES5003P, "Sumikaexcel (registered trademark)" PES5200P, and "Sumikaexcel (registered trademark)" PES7200P (all manufactured by Sumitomo Chemical Co., Ltd.), "Virantage (registered trademark)" VW-10200RFP, and "Virantage (registered trademark)" VW-10700RFP (all manufactured by Solvay Chemical Industries, Ltd.). Other examples include copolymer oligomers of polyethersulfone and polyetherethersulfone as described in JP-A-2004-506789, and commercially available polyetherimide products such as "Ultem (registered trademark)" 1000, "Ultem (registered trademark)" 1010, and "Ultem (registered trademark)" 1040 (all manufactured by SABIC Corporation). An oligomer refers to a polymer with a relatively low molecular weight in which a finite number of monomers, approximately 10 to 100, are bonded. (Manufacturing method) The laminate of the present invention can be produced by several methods, specifically the following methods.

[0033] A first manufacturing method involves impregnating reinforcing fibers with a thermosetting resin composition to form a primary prepreg, attaching a resin film containing the thermosetting resin composition and inorganic porous particles to at least one side of the primary prepreg to form a secondary prepreg, and stacking the secondary prepreg so that the side of the secondary prepreg to which the resin film is attached is in contact with another primary or secondary prepreg. In this case, the primary prepreg typically does not contain inorganic porous particles. The resin film-attached portion forms a first layer, and by stacking the secondary prepreg so that it is in contact with another primary or secondary prepreg, a layer containing reinforcing fibers, i.e., a laminate structure sandwiched between the second layers, is formed. In this method, the thermosetting resin composition contained in the primary prepreg and the thermosetting resin composition contained in the resin film preferably have the same composition from the standpoint of productivity, but they may have different compositions. In order to individually adjust the degree of impregnation of the thermosetting resin composition between the reinforcing fibers or the degree of impregnation of the thermosetting resin composition into the inorganic porous particles, the thermosetting resin composition contained in the primary prepreg and the thermosetting resin composition contained in the resin film may each have a different viscosity. Furthermore, when there is a need to adjust the performance of the prepreg or FRP, such as when it is necessary to adjust the surface tackiness to a specific level, the thermosetting resin compositions may have different compositions. Furthermore, the thermosetting resin composition contained in either or both of the primary prepreg and the resin film may contain a thermoplastic resin.

[0034] A second manufacturing method involves impregnating reinforcing fibers with a thermosetting resin composition to prepare prepregs, and then stacking the prepregs to form a laminate. A resin film containing a thermosetting resin composition and inorganic porous particles is inserted between at least one pair of prepregs to form a first layer. In this case, as with the first manufacturing method, the thermosetting resin composition contained in the prepreg and the thermosetting resin composition contained in the resin film may have the same or different compositions. Furthermore, the thermosetting resin composition contained in either or both of the prepreg and the resin film may contain a thermoplastic resin. This method allows for selective placement of layers containing inorganic porous particles only between necessary layers during lamination, enabling flexible design and reducing costs and weight. Furthermore, by additionally laminating only the resin film, the laminate of the present invention can be produced using existing prepregs that do not contain inorganic porous particles, effectively broadening the scope of application.

[0035] A third manufacturing method involves impregnating reinforcing fibers with a thermosetting resin composition to prepare prepregs, and then layering the prepregs to form a laminate. During this process, inorganic porous particles are dispersed between at least one pair of prepregs. The thermosetting resin composition of the prepreg may contain a thermoplastic resin. Furthermore, a thermosetting resin composition may be simultaneously dispersed to disperse the inorganic porous particles. The dispersed particles and the thermosetting resin composition form a first layer. When only particles are dispersed, the first layer is difficult to form immediately after dispersion. However, by fluidizing the resin by heating or other means for curing, a first layer in which the particles are dispersed in the thermosetting resin composition can be formed. In this case, the inorganic porous particles can be selectively disposed between the required layers. Furthermore, the inorganic porous particles can be dispersed within a limited range between layers, and the mass ratio of the inorganic porous particles can be easily varied within the layers. This allows the inorganic porous particles to be disposed only where impact resistance is required, further reducing cost and weight. Furthermore, since there is no need to prepare a resin film, productivity is excellent. [Example]

[0036] The laminate of the present invention will be described in more detail below with reference to the following examples. The raw materials, production methods, and evaluation methods used in the examples are shown below, but the raw materials and production methods are not limited to those described. The production environment and evaluation of the thermosetting resin compositions in the examples were carried out in an atmosphere of a temperature of 25°C ± 2°C and a relative humidity of 50%, unless otherwise specified. <Thermosetting resin> "EPON (registered trademark)" 825 (bisphenol A type epoxy resin [BisA], manufactured by Mitsubishi Chemical Corporation). ELM434 (tetraglycidyldiaminodiphenylmethane [TGDDM], manufactured by Sumitomo Chemical Co., Ltd.). <Inorganic porous particles> SIO2MS-2.2 2-19μm (porous silica particles, COSPHERIC). <Inorganic non-porous particles> P2011SL-2.5 3-6μm (non-porous silica particles, COSPHERIC). <Organic porous particles> Orgasol 2002D NAT (porous nylon particles, manufactured by Arkema). <Organic non-porous particles> Nylon 12 particles SP-10 (non-porous nylon particles [PA12], manufactured by Toray Industries, Inc.). <Thermoplastic resin> "Sumikaexcel (registered trademark)" PES5003P (polyethersulfone, manufactured by Sumitomo Chemical Co., Ltd.). <Curing agent> "Seikacure (registered trademark)"-S (4,4'-diaminodiphenyl sulfone [4,4'-DDS], manufactured by Wakayama Seika Co., Ltd.). (1) Preparation of thermosetting resin compositions and mixtures The thermosetting resin and thermoplastic resin were kneaded in the ratios shown in Table 1, heated to 150°C or higher, and stirred for 1 hour to dissolve the thermoplastic resin, yielding a transparent viscous liquid.

[0037] After the temperature of this liquid was lowered while kneading, a curing agent was added in the amount of parts by mass shown in Table 1 so that the epoxy equivalent was 1.0, and the mixture was kneaded to obtain thermosetting resin compositions 1 and 2. Then, while heating thermosetting resin composition 1 or 2 to 80°C, the above-mentioned particles were added as shown in Table 2, and the mixture was kneaded to obtain thermosetting resin mixtures of the examples and comparative examples. Note that the mass ratio of thermosetting resin to curing agent was the same in thermosetting resin compositions 1 and 2.

[0038] Hereinafter, the thermosetting resin composition and the thermosetting resin mixture may be simply referred to as the composition and the mixture, respectively. (2) Evaluation method for toughness K of cured thermosetting resin composition or mixture The composition or mixture prepared in (1) was degassed in a vacuum and then poured into a mold with a thickness of 6 mm, using a 6 mm Teflon® spacer. It was then cured in an autoclave at 180°C and 0.6 MPa for 2 hours to obtain a 6 mm thick cured plate. The resulting cured plate was machined into the shape of a test piece specified in ASTM D5045-99(2007) and then subjected to the SENB test according to ASTM D5045-99(2007) to obtain a value. Ten test pieces were prepared, and the average of the measured values ​​was taken as the toughness (K). (3) Method for evaluating the flexural modulus E of a cured thermosetting resin composition or mixture The composition or mixture prepared in (1) was degassed in a vacuum and then poured into a mold with a thickness of 2 mm, using a 2 mm Teflon® spacer. The mixture was then cured in an autoclave at 180°C and 0.6 MPa for 2 hours to obtain a 2 mm thick cured plate. Rectangular test pieces measuring 10 mm wide and 60 mm long were cut from the cured plate and subjected to three-point bending in accordance with JIS K7171 (1994) using an Instron universal testing machine (manufactured by Instron Corporation) at a span of 32 mm and a test speed of 10 mm / min to measure the flexural modulus (E). Six test pieces were prepared, and the average of the measured values ​​was taken as the flexural modulus (E). (4) Evaluation of impregnation in the pores of inorganic porous particles The cured plate obtained by method (2) was cut in the thickness direction at a random position, and the cut surface was polished until the pores of the porous particles could be clearly observed. Platinum was vapor-deposited on the polished cut surface, and then SEM observation was performed at 30,000 times magnification. Ten inorganic porous particles observed on the cut surface were randomly selected and observed. If the cured product of the thermosetting resin composition was confirmed in the pores of one or more inorganic porous particles, it was judged as impregnation (○), and if not, it was judged as not impregnation (×). Examples 1 to 2, Comparative Examples 1 to 4 Compositions and mixtures were prepared as described in (1) above using the compositions shown in Tables 1 and 2, respectively, and the toughness, flexural modulus, and impregnation of the inorganic porous particles into the pores of the cured products were evaluated using the methods shown in (2), (3), or (4) above, respectively. The results are shown in Table 2.

[0039] A comparison between Example 1 and Comparative Example 1 showed that by using inorganic porous particles instead of organic porous particles, the cured product achieved similar high toughness while also improving its flexural modulus.

[0040] A comparison between Example 1 and Comparative Example 2 showed that by using inorganic porous particles instead of organic non-porous particles, the cured product achieved equivalent high toughness while also improving its flexural modulus.

[0041] A comparison between Example 1 and Comparative Example 3 showed that by using inorganic porous particles instead of inorganic non-porous particles, the cured product achieved an equally high flexural modulus while also improving toughness.

[0042] Comparison of Example 1 and Comparative Example 4 shows that the addition of inorganic porous particles improves the toughness of the cured product, and further improves the flexural modulus.

[0043] Comparing Example 1 and Example 2, it was found that by adding inorganic porous particles and a thermoplastic resin to a thermosetting resin, the flexural modulus was further improved while maintaining high toughness.

[0044] [Table 1]

[0045] [Table 2] [Explanation of symbols]

[0046] A: Reinforced fiber B: Thermosetting resin composition C: Inorganic porous particles D: First layer E: Second layer F: Boundary between the first and second layers G: Reinforcing fibers that protrude from the second layer E into the first layer D due to disorder in orientation H: Third layer

Claims

1. a first layer in which inorganic porous particles are dispersed in a resin composition containing a thermosetting resin (hereinafter referred to as a thermosetting resin composition); a second layer containing reinforcing fibers and a thermosetting resin composition, the second layer having a mass ratio of inorganic porous particles to the composition filling the layer (hereinafter referred to as the mass ratio of inorganic porous particles) smaller than that of the first layer; A laminate comprising a stacked configuration in which a first layer is sandwiched between two second layers.

2. 2. The laminate according to claim 1, wherein the thermosetting resin contained in the thermosetting resin composition is an epoxy resin.

3. The laminate of claim 1 , wherein the thermosetting resin composition comprises a thermoplastic resin.

4. 2. The laminate according to claim 1, wherein the inorganic porous particles are silica particles.

5. The laminate according to claim 1 , wherein the inorganic porous particles have an average particle size of 1 μm or more and 100 μm or less.

6. The laminate according to claim 1 , wherein the pores of the inorganic porous particles are impregnated with a thermosetting resin.

7. 2. The laminate of claim 1, wherein the reinforcing fibers are carbon fibers.

8. The laminate according to claim 1 , wherein the mass ratio of the inorganic porous particles in the first layer is 10 times or more the mass ratio of the inorganic porous particles in the second layer.

9. A first prepreg is prepared by impregnating a reinforcing fiber with a thermosetting resin composition, and a first prepreg is formed on at least one side of the first prepreg. A resin film containing a thermosetting resin composition and inorganic porous particles is attached to prepare a second prepreg; A method for manufacturing a laminate in which the surface of the secondary prepreg to which the resin film is attached is stacked so as to be in contact with one surface of another primary or secondary prepreg.

10. A prepreg is prepared by impregnating reinforcing fibers with a thermosetting resin composition, A method for producing a laminate, comprising inserting a resin film containing a thermosetting resin composition and inorganic porous particles between at least one pair of prepregs in a process of forming the laminate by stacking prepregs.

11. A prepreg is prepared by impregnating reinforcing fibers with a thermosetting resin composition, A method for producing a laminate, comprising scattering inorganic porous particles between at least one pair of prepregs in a process of forming the laminate by stacking prepregs.

12. A fiber-reinforced composite material obtained by curing the laminate according to any one of claims 1 to 9.

13. 13. An aircraft component comprising the fiber-reinforced composite material of claim 12.

14. An aircraft comprising a member according to claim 13.

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