Reinforcing fiber substrate and method for producing the same

Abstract

To provide a reinforcing fiber substrate having excellent formability and form stability and capable of stably producing a high-quality, high-precision preform with no slits on a finished product surface even in a complicated shape and to provide a method for producing the same.SOLUTION: There is provided a reinforcing fiber substrate obtained by laminating one or a plurality of reinforcing fiber sheets with a nonwoven fabric sheet on which a nonwoven fabric sheet is disposed on one surface or both surfaces of a reinforcing fiber sheet formed by aligning a reinforcing fiber thread in parallel, followed by fixing with a stitching thread, wherein (a) a resin material for a preform is adhered to at least one of the surface of the stitching thread, the entire surface of the fibers constituting the nonwoven fabric sheet or the surface of the fiber-reinforcing yarn strips and (b) the resin material for a preform is not adhered between two or more adjacent fiber bundles of the reinforcing fiber yarns and between the stitching yarns and fiber bundles of the reinforcing fiber yarns and the reinforcing fiber substrate has an initial shear stiffness in a specific range and a peak load in a specific range of a flexural test.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a reinforced fiber base material suitably used in an injection molding method and a method for producing the same. More specifically, the present invention relates to a reinforced fiber base material capable of stably producing a high-quality and high-precision preform with excellent formability and form stability, having no cuts on the surface of the final product even with a complex shape, and a method for producing the same.

Background Art

[0002] Fiber Reinforced Plastics (FRP) in which reinforcing fibers are impregnated with a matrix resin are widely used in aviation, space, automotive applications, etc. because of their characteristics of being lightweight and having high strength. As a molding method that achieves both productivity and high strength of FRP, for example, injection molding methods such as Resin Transfer Molding (RTM) and Vacuum assisted Resin Transfer Molding (VaRTM) can be mentioned. The injection molding method is a molding method in which a fiber-reinforced laminate made of a dry reinforced fiber base material not preliminarily impregnated with a matrix resin is placed in a mold, and a liquid and low-viscosity matrix resin is injected, and then the matrix resin is impregnated and solidified to produce FRP.

[0003] As a reinforced fiber base material used in the injection molding method, a laminate obtained by laminating unidirectional layers (reinforced fiber sheets) of reinforcing fibers having a predetermined basis weight in a plurality of directions such as biaxial or triaxial is proposed as a reinforced fiber base material that is penetrated and stitched integrally in the thickness direction of the laminate by a stitch yarn. Since this reinforced fiber base material has a plurality of reinforcement directions in one sheet, there is an advantage that the lamination work is simplified and FRP can be obtained at low cost.

[0004] The injection molding method is excellent in the productivity of FRP, but since it is necessary to make the matrix resin have a low viscosity, compared with FRP formed from the high-viscosity matrix resin used for prepregs, the mechanical properties may not be fully exhibited in some cases. Therefore, as a solution to the above, a reinforcing fiber base material in which a plurality of reinforcing fiber sheets having a specified basis weight and thermoplastic fiber webs (nonwoven sheets) having a specified thickness are laminated has been proposed. By arranging the nonwoven sheet between layers, the mechanical properties in the compression after impact (CAI) test generally used to characterize the impact resistance of the structure can be improved.

[0005] In the injection molding method of a product having a three-dimensional shape, in some cases, a preform in which a laminate of a reinforcing fiber base material is previously shaped into the product shape and fixed and integrated is used. The manufacturing process of the preform can be divided into a laminating process of laminating the reinforcing fiber base materials cut to desired dimensions to form a laminate, a preform process of shaping the laminate into the product shape and then integrating it by heating and cooling to form a preform, and a conveying process of conveying the preform to a storage location.

[0006] For the production of the preform, a reinforcing fiber base material with a preform resin material previously fixed on its surface is generally used. Patent Document 1 exemplifies a multilayer base material in which a plurality of biaxial reinforcing fiber base materials are laminated and integrated with an engaging material such as particles or a nonwoven sheet. Techniques for improving the formability and handleability have been proposed by defining the orientation direction of the reinforcing fiber yarns and the relationship between the melting point of the engaging material and the melting point of the stitch yarn.

[0007] Next, Patent Document 2 exemplifies a method of improving the formability of a reinforcing fiber base material by making a cut in the reinforcing fiber base material to partially cut the reinforcing fibers.

[0008] In addition, Patent Document 3 exemplifies a reinforced fiber base material with a resin material for a preform fixed to its surface. After fixing the resin material for a preform to the surface of the reinforced fiber base material, by varying the relative positions of a plurality of reinforced fiber yarns constituting the reinforced fiber base material, a reinforced fiber base material is proposed in which the resin material for a preform fixed across two or more reinforced fiber yarns is peeled off from a part of the two or more reinforced fiber yarns.

[0009] Furthermore, Patent Document 4 proposes a composite nonwoven fabric sheet in which composite particles composed of a mixture of a polymer and a conductive material are dispersed in a nonwoven fabric sheet as a technique for improving the conductivity of FRP.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0011] However, a reinforced fiber base material with a resin material for a preform fixed to its surface or between layers as described in Patent Document 1 has a large deformation resistance and may develop wrinkles during preform formation, resulting in problems such as molding defects due to wrinkles and a decrease in appearance quality. On the other hand, when the resin material for a preform is not used, although the formability of the reinforced fiber base material is relatively excellent, its shape stability is inferior. When the reinforcing fibers are disturbed during resin injection, when the reinforcing fibers are disturbed during lamination of the reinforced fiber base material or conveyance of the preform, or when the three-dimensional shape of the preform cannot be maintained and a molded product of the desired shape cannot be obtained.

[0012] Next, in the conventional reinforcing fiber base material with cuts made in the reinforcing fiber base material as described in Patent Document 2, although a product with a smooth surface can be obtained, there are cases where the reinforcing fibers become discontinuous and the mechanical properties deteriorate, or where the cuts can be visually recognized from the product surface, thus impairing the appearance quality.

[0013] Also, in the technique of peeling the resin material for the fixed preform as described in Patent Document 3, although a reinforcing fiber base material fixed with stitch yarns is exemplified as a reinforcing fiber base material applicable to the same document, there is no description regarding a specific application method, and only a reinforcing fiber base material without stitches is disclosed in the examples. In fact, when applying the technique of the same document to a reinforcing fiber base material fixed with stitch yarns, there are cases where the desired formability cannot be exhibited, or where the stitches are broken and the form of the reinforcing fiber base material cannot be maintained.

[0014] Furthermore, simply arranging the composite nonwoven fabric sheet as described in Patent Document 4, as is clear from the fact that a resin material for a preform different from the composite nonwoven fabric sheet is additionally used in the preform process in the same document, cannot be used for stabilizing the form of the reinforcing fiber base material or the preform.

[0015] Furthermore, since conventional reinforcing fiber base materials with relatively excellent formability are soft and lack stiffness, the surplus of the reinforcing fiber base material generated in the process of shaping it into the product shape buckles on the spot, resulting in a large number of small wrinkles or causing disorder of the reinforcing fibers. This problem is particularly prominent in reinforcing fiber base materials that do not use a resin material for the preform. On the other hand, although conventional reinforcing fiber base materials with poor formability are excellent in form stability, as described above, they have a large deformation resistance and may generate large wrinkles during preform formation.

[0016] Thus, in the prior art as described above, it has been extremely difficult to obtain a reinforcing fiber base material that is excellent in formability and form stability, can stably manufacture a high-quality and high-precision preform without cuts on the final product surface even with a complex shape.

[0017] Therefore, paying attention to the above problems, an object of the present invention is to provide a reinforced fiber base material capable of stably manufacturing a high-quality and high-precision preform that is excellent in formability and form stability, has no cuts on the surface of the final product even with a complex shape, and a manufacturing method thereof. In particular, the present invention provides a reinforced fiber base material in which wrinkles due to excess of the reinforced fiber base material are less likely to occur and a manufacturing method thereof.

Means for Solving the Problems

[0018] As a result of investigations to solve the above problems, the present inventors have found that the fixing form of the resin material for the preform spanning between the stitch yarn and the fiber bundle of the reinforcing fiber yarn affects the formability. Furthermore, it has been found that form stability is required for the lamination process and the conveying process, and formability is required for the preform process. Therefore, when examining the influence of the fixing form of the resin material for the preform on the process passability of each process and the influence on the formability of the reinforced fiber base material, it has been found that by using the reinforced fiber base material of the present invention shown below for the first time, the form is stable in the lamination process and the conveying process, and excellent formability is exhibited in the preform process. 〔1〕A reinforced fiber base material in which one or more non-woven fabric-attached reinforced fiber sheets, in which a non-woven fabric sheet is disposed on one or both surfaces of a reinforced fiber sheet formed by aligning reinforcing fiber yarns in parallel, are laminated and fixed with stitch yarns, (a) The resin material for the preform is fixed to at least one of the surface of the stitch yarn, the entire surface of the fibers constituting the non-woven fabric sheet, or the surface of the fiber-reinforced yarn, (b) The resin material for the preform does not span and is not fixed between the fiber bundles of two or more adjacent reinforcing fiber yarns and between the stitch yarn and the fiber bundle of the reinforcing fiber yarn, (c) The initial shear rigidity is 1.5×10 -5 N / mm / gsm or more and 1.5×10 -4 N / mm / gsm or less, (d) The range of the peak load in the bending test is 2.7×10 -9 N / gsm 3 or more and 1.4×10 -8 N / gsm 3 or less, A reinforced fiber base material, characterized in that it is as described. 〔2〕The basis weight of the nonwoven fabric sheet is 1 gsm or more and 50 gsm or less, The reinforced fiber base material according to 〔1〕, characterized in that. 〔3〕The average fiber diameter of the nonwoven fabric sheet is 1 μm or more and 100 μm or less, The reinforced fiber base material according to 〔1〕, characterized in that. 〔4〕The surface of the resin material for preform fixed to the nonwoven fabric sheet is a smooth surface, The reinforced fiber base material according to 〔1〕, characterized in that. 〔5〕50% or more and 100% or less of the surface of the nonwoven fabric sheet is coated with the resin material for preform, The reinforced fiber base material according to 〔1〕, characterized in that. 〔6〕50% or more and 100% or less of the surface of the reinforced fiber sheet is coated with the resin material for preform, The reinforced fiber base material according to 〔1〕, characterized in that. 〔7〕The basis weight of the resin material for preform is 3 gsm or more and 50 gsm or less, The reinforced fiber base material according to 〔1〕, characterized in that. 〔8〕The resin material for preform is granular, The reinforced fiber base material according to 〔1〕, characterized in that. 〔9〕The average particle diameter of the resin material for preform is 50 μm or more and 1000 μm or less, The reinforced fiber base material according to 〔8〕, characterized in that. 〔10〕The breaking elongation of the stitch yarn is 15% or more, The reinforced fiber base material according to 〔1〕, characterized in that. 〔11〕The melting point Tmb (°C) of the resin material for preform is lower than the melting point Tmv (°C) of the nonwoven fabric sheet and the melting point Tms (°C) of the stitch yarn, The reinforced fiber base material according to 〔1〕, characterized in that. 〔12〕The fixing method of the stitch yarn is tricot knitting, The reinforced fiber base material according to 〔1〕, characterized in that. 〔13〕Among the reinforced fiber sheets with nonwoven fabric laminated in multiple layers, a first-direction reinforced fiber sheet in which the alignment direction of the reinforced fiber yarns is the first direction and a second-direction reinforced fiber sheet in which the alignment direction of the reinforced fiber yarns is the second direction are included, and the first direction and the second direction are orthogonal to each other, The reinforced fiber base material according to 〔1〕, characterized in that. A method for manufacturing a reinforced fiber base material, comprising laminating one or more non-woven fabric-attached reinforced fiber sheets, in which a non-woven fabric sheet is disposed on one or both surfaces of a reinforced fiber sheet formed by aligning reinforcing fiber filaments in parallel, and fixing the sheets with a stitching thread, (a) fixing a resin material for preform to at least one outermost surface of the reinforced fiber base material, (b) applying a tensile strain of 10% or more in a direction (direction A) for applying shear deformation in the in-plane direction of the reinforced fiber base material, and then (c) applying a tensile strain of 10% or more in a direction (direction B) different from the direction (direction A) for applying shear deformation, characterized in that. A method for manufacturing a reinforced fiber base material. 〔15〕The method for manufacturing a reinforced fiber base material according to 〔14〕, characterized in that the direction (direction A) for applying shear deformation is a stitching direction. 〔16〕The method for manufacturing a reinforced fiber base material according to 〔14〕, characterized in that the direction (direction A) for applying shear deformation is a direction orthogonal to the stitching direction.

Advantages of the Invention

[0019] According to the present invention, a reinforced fiber base material and a method for manufacturing the same, which are excellent in formability and form stability, can stably manufacture a high-quality and high-precision preform without cuts on the surface of the final product even with a complex shape. In particular, a reinforced fiber base material in which wrinkles due to excess of the reinforced fiber base material are unlikely to occur and a method for manufacturing the same can be obtained.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0021] The reinforced fiber base material of the present invention is a reinforced fiber base material in which one or more non-woven fabric-attached reinforced fiber sheets, in which non-woven fabric sheets are arranged on one or both surfaces of a reinforced fiber sheet formed by aligning reinforced fiber yarns in parallel, are laminated and fixed with stitch yarns, and (a) a resin material for preform is fixed to at least one of the surface of the stitch yarn, the entire surface of the fibers constituting the non-woven fabric sheet, or the surface of the fiber-reinforced yarns, (b) the resin material for preform does not adhere across between fiber bundles of two or more adjacent reinforced fiber yarns and between the stitch yarn and the fiber bundles of the reinforced fiber yarns, (c) the initial shear rigidity is 1.5×10 -5 N / mm / gsm or more and 1.5×10 -4 N / mm / gsm or less, and (d) the range of the peak load in the bending test is 2.7×10 -9 N / gsm 3 or more and 1.4×10 -8 N / gsm 3 or less, and is characterized by that.

[0022] Hereinafter, the present invention will be described in detail with reference to the drawings together with embodiments.

[0023] [Overview of Reinforced Fiber Substrate] FIG. 1 shows an embodiment of the reinforced fiber substrate of the present invention. The reinforced fiber substrate 8 of the present invention includes a reinforced fiber sheet (1, 2, 3, 4) formed by aligning reinforced fiber yarns Y in parallel, a non-woven fabric sheet (5A, 5B) disposed on one or both surfaces of the reinforced fiber sheet, a stitch yarn 6, and a resin material for preform as components. The reinforced fiber sheet (1, 2, 3, 4) and the non-woven fabric sheet (5A, 5B) are stitched and integrated with the stitch yarn 6 in the stitching direction (woven direction) indicated by the arrow by a vertically moving needle 7 to form the reinforced fiber substrate 8.

[0024] Since the reinforced fiber yarns constituting the reinforced fiber substrate are hardly bent, the mechanical properties of the molded product after matrix resin injection are excellent, and since a plurality of layers can be arranged simultaneously, the arrangement efficiency is good, which is preferable. Therefore, it can be suitably used particularly for large structural (especially primary structure) members of transportation equipment (especially aircraft).

[0025] [Reinforced Fiber Sheet] The reinforced fiber sheet used for the reinforced fiber substrate of the present invention is composed of reinforced fiber yarns aligned in parallel.

[0026] The reinforced fiber sheet according to the present invention is preferably in a form composed of continuous fiber reinforced fiber yarns because excellent mechanical properties can be obtained.

[0027] Examples of the reinforced fiber yarns include carbon fiber, glass fiber, aramid fiber, alumina fiber, silicon carbide fiber, boron fiber, and silicon carbide fiber. Among them, from the viewpoints of mechanical strength and light weight, it is preferable to use carbon fiber having a high specific elastic modulus.

[0028] The reinforcing fiber yarn is formed by bundling 1,000 to 60,000 individual reinforcing fibers (also called single filaments). Preferably, 3,000 to 50,000 single filaments are used for one reinforcing fiber yarn, and more preferably 6,000 to 24,000 single filaments are used.

[0029] When selecting carbon fiber as the reinforcing fiber yarn, any type of carbon fiber can be used according to the application. However, from the perspective of compatibility with impact resistance, tensile strength, and compressive strength, the tensile modulus of elasticity of the carbon fiber is preferably at least 200 GPa or more, more preferably in the range of 200 to 600 GPa, and even more preferably in the range of 250 to 450 GPa. Also, from the perspective of the strength of the carbon fiber, since a composite material having mechanical properties such as high rigidity, high tensile strength, and high compressive strength can be obtained, carbon fibers with a tensile strength of 4.0 GPa or more are preferably used, more preferably in the range of 4.0 to 7.5 GPa, and even more preferably in the range of 5.0 to 7.0 GPa. In addition, the tensile elongation is also an important factor, and it is preferable that the carbon fiber has a high tensile elongation of 1.5% or more. Therefore, carbon fibers having the characteristics of a tensile modulus of elasticity of at least 200 GPa or more, a tensile strength of at least 4.0 GPa or more, and a tensile elongation of at least 1.5% or more are most suitable.

[0030] Examples of commercially available carbon fibers include "Torayca (registered trademark)" T1100GC-12K, "Torayca (registered trademark)" T800SC-12K, "Torayca (registered trademark)" T700SC-12K (all manufactured by Toray Industries, Inc.).

[0031] Examples of the form of forming a reinforcing fiber sheet using the reinforcing fiber yarn include a unidirectional form in which the reinforcing fiber yarns are aligned in one direction, and a non-crimp form in which the fibers aligned in one direction are laminated on one axis or multiple axes.

[0032] [Fiber bundle of reinforcing fiber yarn] In the present invention, the fiber bundle of the reinforcing fiber yarn refers to a bundle of reinforcing fiber yarns oriented in one direction, which is divided by stitch yarns for fixing the reinforcing fiber base material.

[0033] In the present invention, it is important that the resin material for the preform does not adhere across between fiber bundles of two or more adjacent reinforcing fiber yarns and between the stitch yarn and the fiber bundle of the reinforcing fiber yarn.

[0034] Here, Yg between fiber bundles of two or more adjacent reinforcing fiber yarns is a section defined by the relationship between the stitch length and the orientation direction of the reinforcing fiber yarns, as shown in FIG. 2. It is a section extending in the orientation direction of the reinforcing fiber yarns over one stitch length starting from the portion 61 where the stitch yarn penetrates the reinforcing fiber base material. Since this section is a section that shifts with the shear deformation of the reinforcing fiber base material, by not adhering the preform resin material across this section, the resistance to shear deformation of the reinforcing fiber base material can be reduced, and the initial shear rigidity described later can be decreased. Note that the stitch length is the repeating unit of sewing integration in the stitching direction, and the gauge length is the distance between adjacent stitch yarns in the direction orthogonal to the stitching direction (that is, the distance between adjacent needles).

[0035] [Nonwoven fabric sheet] In the present invention, the nonwoven fabric sheet refers to a sheet in which fibers are oriented in one direction or randomly and the fibers are bonded together by alternating current, and / or heat fusion, and / or adhesion.

[0036] FIG. 3 shows an embodiment of the nonwoven fabric sheet of the present invention. In FIG. 3, the nonwoven fabric sheet (5A) is disposed on one side of the reinforcing fiber sheet. Also, in the present invention, although not shown, it is also preferable to dispose the nonwoven fabric sheet on both sides of the reinforcing fiber sheet.

[0037] Also, it is important that this nonwoven fabric sheet is disposed on at least one outermost surface of the reinforcing fiber base material.

[0038] Note that hereinafter, the "surface of the nonwoven fabric sheet" means the surface of the entire fibers constituting the nonwoven fabric sheet, as described above.

[0039] Inside the reinforcing fiber base material, that is, in the nonwoven fabric sheet 5B disposed between layers of one reinforcing fiber sheet and another reinforcing fiber sheet, it is not necessary to fix the resin material 9 for preform, but in terms of improving the form stability when forming a preform, it is preferable to fix the resin material 9 for preform.

[0040] As the fiber constituting the nonwoven fabric sheet of the reinforcing fiber base material of the present invention, for example, synthetic fibers can be used, but as long as the resin material for preform can be fixed on the surface and the mechanical properties in the compression after impact (CAI) test can be improved, the material is not particularly limited.

[0041] The material of the synthetic fiber used for the nonwoven fabric sheet can be at least one selected from the group consisting of polyamide, polypropylene, polysulfone, polyetherimide, polyethersulfone, polyetherketone, polyetheretherketone, aromatic polyamide, aromatic polyester, polyarylene sulfide, aromatic polycarbonate, polyarylene oxide, thermoplastic polyimide, polyamideimide, polybutylene terephthalate, polyethylene terephthalate, and polyethylene. Also, depending on the application, it can be used by mixing with a partially thermosetting resin. Among them, polyamide, aromatic polyamide, polyarylene sulfide, and polyetherimide are particularly preferably used from the viewpoints of high heat resistance, high strength, and sheet processability.

[0042] Further, from the point that a highly tough layer can be formed between the layers of the FRP and the mechanical properties (especially CAI) can be enhanced, the synthetic fiber used as the stitch yarn is preferably a copolyamide containing at least two polyamide components selected from polyamide 6, polyamide 6-6, polyamide 6-10, polyamide 12, and polyamide 6-I.

[0043] From the viewpoint of suppressing the decrease in mechanical properties of FRP under hygrothermal conditions, it is preferable to contain polyamide 12 with a low water absorption rate. Therefore, the proportion of polyamide 12 in the synthetic fiber is 5 mol% or more, preferably 50 mol% or more, and more preferably 80 mol% or more. Examples of resin materials that can be copolymerized with polyamide 12 include polyamide 6, polyamide 6-6, polyamide 4-6, polyamide 6-10, polyamide 6-12, polyamide 6-T, polyamide 6-I, polyamide 6-6 / 6-T, polyamide 6-6 / 6-I, polyamide 6-6 / 6-T / 6-I, and the like. Particularly preferred examples include polyamide 6, polyamide 6-6, polyamide 6-10, polyamide 12, and polyamide 6-I. It is also preferable to use these synthetic fibers as a mixture according to the required properties such as processability, heat resistance, and toughness.

[0044] The nonwoven fabric sheet according to the reinforcing fiber base material of the present invention preferably has a basis weight of 1 gsm or more and 50 gsm or less. Note that gsm is equal to g / m 2 and is equal to.

[0045] By making the basis weight larger than the lower limit, the amount of the resin material for preform fixed to the nonwoven fabric sheet increases, and the amount of the resin material for preform fixed to the nonwoven fabric sheet can be increased. On the other hand, by making it below the upper limit, the burial and impregnation of the resin material for preform into the nonwoven fabric sheet can be suppressed, so that the peeling of the reinforcing fiber base material from the preform can be prevented.

[0046] More preferably, the nonwoven fabric sheet according to the reinforcing fiber base material of the present invention has a basis weight of 5 gsm or more and 20 gsm or less. By setting the basis weight to 5 gsm or more and 20 gsm or less, the interlayer toughness, strength, and elastic modulus can be improved in a well-balanced manner. Also, by setting it to 5 gsm or more, the local variation in the basis weight of the nonwoven fabric sheet can be reduced, so that it is easy to uniformly reinforce the entire interlayer of the FRP. Further, by setting it to 20 gsm or less, the thickness of the nonwoven fabric sheet becomes thinner, so that the proportion of the reinforcing fibers contained in the FRP increases, and an FRP having excellent mechanical properties can be obtained.

[0047] The nonwoven sheet according to the reinforcing fiber base material of the present invention preferably has an average fiber diameter of 1 μm or more and 100 μm or less.

[0048] By setting the average fiber diameter to be equal to or greater than the lower limit, it becomes easier to fix the resin material for the preform on the surface of the nonwoven fabric. On the other hand, by setting it to be equal to or less than the upper limit, since the fiber diameter becomes thinner, even when the basis weight of the nonwoven sheet is small, the surface area increases, and the amount of resin fixed can be increased. The nonwoven sheet according to the reinforcing fiber base material of the present invention more preferably has an average fiber diameter of 5 μm or more and less than 80 μm, and even more preferably 10 μm or more and less than 60 μm. When the average fiber diameter is within the above preferable range, the flow resistance is small, and it is possible to suppress the inhibition of resin impregnation and the generation of voids during resin injection. On the other hand, since the thickness between layers when made into FRP becomes small, the proportion of reinforcing fibers contained in the FRP increases, and an FRP with excellent mechanical properties can be obtained.

[0049] [Reinforcing fiber sheet with nonwoven fabric] The reinforcing fiber sheet with nonwoven fabric according to the reinforcing fiber base material of the present invention is formed by arranging a nonwoven sheet on one side or both sides of the reinforcing fiber sheet.

[0050] At this time, when a plurality of reinforcing fiber sheets with nonwoven fabric in which the nonwoven sheet is arranged on one side of the reinforcing fiber sheet are laminated, one nonwoven sheet is arranged between adjacent layers of the reinforcing fiber sheets. On the contrary, when a plurality of reinforcing fiber sheets with nonwoven fabric in which the nonwoven sheet is arranged on both sides of the reinforcing fiber sheet are laminated, two nonwoven sheets are arranged between adjacent layers of the reinforcing fiber sheets.

[0051] Since the process of arranging the nonwoven sheet can be halved and the manufacturing apparatus and process can be simplified, it is preferable that the nonwoven sheet is arranged on one side of the reinforcing fiber sheet.

[0052] The reinforcing fiber sheet used for the reinforcing fiber base material of the present invention includes a first-direction reinforcing fiber sheet in which the alignment direction of the reinforcing fiber yarns is the first direction and a second-direction reinforcing fiber sheet in which the alignment direction of the reinforcing fiber yarns is the second direction among the reinforcing fiber sheets with nonwoven fabric laminated in multiple layers, and it is preferable that the first direction and the second direction are orthogonal to each other.

[0053] By making the first direction and the second direction orthogonal to each other, the reinforcing fiber base material can be sheared and deformed to the same extent in a plurality of shear-deformable in-plane directions. Therefore, even when shaping a laminate reinforced in a plurality of directions by the reinforcing fiber yarns into a product having a complex shape, since there is room for shear deformation in the reinforcing fiber base material, it is difficult to cause tension by the reinforcing fiber yarns and it is easy to shape.

[0054] From the viewpoint of simplifying the lamination work, among the reinforcing fiber sheets with nonwoven fabric laminated in multiple layers, it is preferable that the alignment direction of the reinforcing fiber yarns is three or more directions. In particular, for example, as [(0° / 90°) / (+45° / -45°)], while making the alignment direction of the reinforcing fiber yarns in an orthogonal relationship, increasing the orientation direction of the reinforcing fiber yarns can result in a configuration that is reinforced in a plurality of directions and has excellent formability. Since such a reinforcing fiber base material has a plurality of reinforcing directions in one sheet, there is an advantage that the lamination work is simplified and FRP can be obtained at low cost.

[0055] From the viewpoint of further improving the formability, it is more preferable that the alignment direction of the reinforcing fiber yarns of the plurality of layers of reinforcing fiber sheets constituting the reinforcing fiber sheet with nonwoven fabric is only the first / second direction. Such a reinforcing fiber base material in which the orientation direction of the reinforcing fiber yarns is biaxial is easier to shear-deform and has excellent formability compared to a triaxial or quadraxial base material, and it is easy to reduce the initial shear rigidity.

[0056] [Stitch yarn] As the stitch yarn for the reinforcing fiber base material of the present invention, for example, synthetic fibers can be used, but it only needs to be usable for fixing the reinforcing fiber sheet and the nonwoven fabric sheet, and the material is not particularly limited.

[0057] When using synthetic fibers as the stitch yarn, the material can be the same as the synthetic fibers used for the non-woven fabric sheet.

[0058] Also, from the perspective of improving the morphological stability of the reinforcing fiber substrate, when using synthetic fibers as the stitch yarn, it is preferably a copolyamide containing at least two polyamide components selected from polyamide 6, polyamide 6-6, polyamide 6-10, polyamide 12, and polyamide 6-I. When the reinforcing fiber substrate undergoes shear deformation, a tensile load may be applied to the stitch yarn. However, with the above configuration, even when a certain tensile load is applied, the stitch yarn is less likely to undergo plastic deformation and break, and the form as a reinforcing fiber substrate can be maintained even when the reinforcing fiber substrate is formed into a complex shape.

[0059] Also, similar to the non-woven fabric sheet, from the perspective of suppressing the reduction in mechanical properties under the wet heat conditions of FRP, it is preferably contained polyamide 12 with a low water absorption rate. Therefore, the proportion of polyamide 12 in the synthetic fiber is 5 mol% or more, preferably 50 mol% or more, and more preferably 80 mol% or more. Examples of the resin material that can be copolymerized with polyamide 12 include polyamide 6, polyamide 6-6, polyamide 4-6, polyamide 6-10, polyamide 6-12, polyamide 6-T, polyamide 6-I, polyamide 6-6 / 6-T, polyamide 6-6 / 6-I, polyamide 6-6 / 6-T / 6-I, and the like. Particularly preferred examples include polyamide 6, polyamide 6-6, polyamide 6-10, polyamide 12, and polyamide 6-I. It is also preferable to use these synthetic fibers as a mixture according to the required properties such as processability, heat resistance, and toughness.

[0060] The fiber diameter of the stitch yarn according to the present invention is preferably 1 μm or more and less than 500 μm, more preferably 5 μm or more and less than 80 μm, and even more preferably 10 μm or more and less than 60 μm. By setting the fiber diameter within the above preferred range, while reducing the cross-sectional area of the stitch yarn, the deformation resistance in the longitudinal direction is appropriately maintained. Thereby, while firmly maintaining the fixation between the reinforcing fiber sheet and the nonwoven fabric, the initial shear rigidity of the reinforcing fiber base material can be reduced. Furthermore, since the meandering of the reinforcing fiber yarns when the reinforcing fiber base materials are laminated can be suppressed, the mechanical properties are also improved.

[0061] For the same reason as the fiber diameter, the fineness of the stitch yarn related to the reinforcing fiber base material of the present invention is preferably 10 dtex or more and 500 dtex or less, and more preferably 20 dtex or more and 300 dtex or less.

[0062] Here, the fineness of the stitch yarn in the present invention is a value obtained by measuring in accordance with JIS L1013 (2010) as follows. First, cut such a stitch yarn to a length of 90 cm. Next, using an electronic balance capable of measuring the number of grams up to five decimal places, measure the mass of five samples, and average the values converted to the mass per 10,000 m as the fineness (unit: dtex).

[0063] Here, the breaking elongation of the stitch yarn is a value obtained by measuring in accordance with "Single Yarn Tensile Strength and Elongation Ratio" of JIS L1095 (2010) as follows, and the elongation ratio when the single yarn breaks is defined as the breaking elongation.

[0064] In the present invention, the breaking elongation of the stitch yarn is preferably 15% or more, and more preferably 30% or more. By setting the breaking elongation of the stitch yarn to 15% or more, even when the reinforcing fiber base material is greatly deformed, the stitch does not break, so that the reinforcing fibers can be preferably arranged along the shape. Also, by setting the breaking elongation of the stitch yarn to 30% or more, even when the reinforcing fiber base material is locally greatly deformed, the stitch does not break, so that the form of the sheet can be maintained.

[0065] [Resin Material for Preform] In the reinforcing fiber base material of the present invention, as the resin material for the preform, a thermoplastic resin, a thermosetting resin, or a mixture thereof can be appropriately selected and used. Such a resin material for the preform needs to be in a crystalline state or a glass state at room temperature and have the property of melting or softening by heat.

[0066] As the thermoplastic resin used as the resin material for the preform, for example, at least one selected from the group consisting of polyamide, polypropylene, polysulfone, polyetherimide, polyethersulfone, polyetherketone, polyetheretherketone, aromatic polyamide, aromatic polyester, polyarylene sulfide, aromatic polycarbonate, polyarylene oxide, thermoplastic polyimide, polyamideimide, polybutylene terephthalate, polyethylene terephthalate, and polyethylene can be used. When the resin material is mainly composed of a thermoplastic resin, the handleability is improved when spraying and fixing it on the surface of the reinforcing fiber fabric, and further when laminating the reinforcing fiber fabric and deforming it into a three-dimensional shape and then bonding the layers, and the productivity is improved. Here, the main component refers to the component with the largest proportion among the components constituting the resin material.

[0067] As the form of the resin material for the preform, a resin material for the preform in the form of fibers, powder, etc. can be used. The fixing location can be selected from at least one of the surface of the stitch yarn, the entire surface of the fibers constituting the non-woven fabric sheet, and the surface of the reinforcing fiber yarn. As the fixing method, after spraying the resin material for the preform on at least one of the surface of the stitch yarn, the entire surface of the fibers constituting the non-woven fabric sheet, and the surface of the reinforcing fiber yarn, heating and softening it, the resin materials for the preform fixed on the surface of the stitch yarn, the entire surface of the fibers constituting the non-woven fabric sheet, and the surface of the reinforcing fiber yarn are bonded together, and then cooled and solidified. Also, a method of spraying a liquid resin material for the preform on at least one surface of the surface of the stitch yarn, the entire surface of the fibers constituting the non-woven fabric sheet, and the surface of the reinforcing fiber yarn and then solidifying it can be exemplified.

[0068] In the reinforced fiber base material of the present invention, it is important that the resin material for preform adheres to at least one of the surface of the stitch yarn exposed on the outermost surface of the reinforced fiber base material where the nonwoven fabric sheet is disposed, the entire surface of the fibers constituting the nonwoven fabric sheet disposed on the outermost surface of the reinforced fiber base material, or the surface of the fiber reinforced yarn facing the nonwoven fabric sheet disposed on the outermost surface of the reinforced fiber base material.

[0069] Further, when the reinforced fiber base material is laminated, pressed, and heated so that the resin material for preform fixed to at least one of the surface of the stitch yarn, the entire surface of the fibers constituting the nonwoven fabric sheet disposed on the outermost surface of the reinforced fiber base material, or the surface of the fiber reinforced yarn facing the nonwoven fabric sheet disposed on the outermost surface of the reinforced fiber base material faces the adjacent reinforced fiber base material, the resin material for preform adheres to the adjacent reinforced fiber base material, and the effect of maintaining the shape of the deformed reinforced fiber base material can be exhibited.

[0070] [Preferred embodiment regarding the form of the resin material for preform fixed] In the reinforced fiber base material of the present invention, it is preferable that the surface of the fixed resin material for preform is a smooth surface.

[0071] FIG. 6 shows an enlarged plan view of the reinforced fiber base material 8 in which the surface of the fixed resin material 9 for preform is a smooth surface.

[0072] The smooth surface refers to a state in which there are no sharp portions or fine irregularities on the surface and it is composed of a rounded and smooth curved surface.

[0073] With such a configuration, even when the reinforced fiber base materials laminated during shaping rub against each other, peeling of the resin material for preform from the reinforced fiber base material, and displacement or cutting of the nonwoven fabric sheet, the reinforced fiber yarn, and the stitch yarn can be suppressed. This is because it is difficult for the nonwoven fabric sheet and the reinforced fiber yarn to catch on the surface of the resin material for preform. Further, since the friction coefficient of the surface of the reinforced fiber base material is reduced, there is an effect that wrinkles are less likely to occur even when shaping a thick laminate having a thickness exceeding 2 mm.

[0074] As a method for making the surface of the resin material for the preform smooth, an example is a method in which a liquid resin material for the preform is sprayed onto the surface of a nonwoven fabric sheet, a stitch thread, or a reinforcing fiber yarn and then solidified. Further, when using a granular resin material for the preform, an example is a method in which the resin material for the preform is heated to a temperature equal to or higher than the melting point Tmb (°C) while being scattered on the surface of a nonwoven fabric, a stitch thread, or a reinforcing fiber yarn, melted, and then cooled and solidified. Furthermore, an example is a method in which a resin material for the preform (for example, FIG. 3) whose surface is not a smooth surface is heated to a temperature equal to or higher than the melting point Tmb (°C), melted, and then cooled and solidified.

[0075] It is preferable that 50% or more and 100% or less of the surface of the nonwoven fabric sheet according to the reinforcing fiber base material of the present invention is covered with the resin material for the preform.

[0076] With such a configuration, even when the nonwoven fabric sheet is deformed or partially turned inside out when the reinforcing fiber base material is shaped into a product shape, the resin material for the preform will be present on the surface of the reinforcing fiber base material. Therefore, since the resin material for the preform is present if the nonwoven fabric sheet is present on the surface of the reinforcing fiber base material, the reinforcing fiber base materials can be firmly fixed to each other when laminated and integrated, and a preform with excellent morphological stability can be obtained.

[0077] For the same reason, it is preferable that the nonwoven fabric sheet according to the reinforcing fiber base material of the present invention is disposed over the entire surface of at least one side of the reinforcing fiber sheet. Here, the surface of the reinforcing fiber sheet means one surface of the sheet-like material.

[0078] The coverage rate of the resin material for the preform on the surface of the nonwoven fabric sheet can be measured by the following method. First, cut out a 100 mm × 100 mm reinforced fiber substrate from the central portion in the width direction of the reinforced fiber substrate. Next, using a microscope, photograph the surface of the nonwoven fabric sheet to which the resin material for the preform of the reinforced fiber substrate is fixed at a magnification of 300 times to prepare an evaluation image. Subsequently, measure the length Lv of the fibers constituting the nonwoven fabric sheet included in the evaluation image. Further, measure the length Lb of the portion of the fibers constituting the nonwoven fabric sheet to which the resin material for the preform is fixed, and divide it by the length Lv of the fibers constituting the nonwoven fabric sheet, whereby the coverage rate of the resin material for the preform is obtained. In the fibers constituting the nonwoven fabric sheet in the evaluation image, if there is a section where the resin material for the preform is fixed to any part in the circumferential direction, that section is regarded as the portion to which the resin material for the preform is fixed.

[0079] The above measurement can be carried out, for example, using a Keyence digital microscope VHX-8000.

[0080] Preferably, 50% or more and 100% or less of the surface of the reinforced fiber sheet is covered with the resin material for the preform. The coverage rate of the resin material for the preform on the surface of the reinforced fiber sheet can be measured by the following method. First, cut out a 100 mm × 100 mm reinforced fiber substrate from the central portion in the width direction of the reinforced fiber substrate. Next, using a microscope, photograph the surface of the reinforced fiber substrate to which the resin material for the preform is fixed at a magnification of 100 times to prepare an evaluation image. Subsequently, measure the area Sc of the reinforced fiber yarns, the area Sb of the resin material for the preform on the reinforced fiber yarns, the area Ss of the stitch yarns on the reinforced fiber yarns, and the area Sv of the nonwoven fabric sheet on the reinforced fiber yarns included in the evaluation image. Subsequently, the coverage rate Rcb of the resin material for the preform is obtained by the following formula 1. Rcb = (Sc - Sb - Ss) ÷ Sc × 100 ··· (Formula 1)

[0081] The above measurement can be carried out, for example, using a Keyence digital microscope VHX-8000.

[0082] The resin material for preform according to the reinforcing fiber base material of the present invention preferably has a basis weight of 3 gsm or more and 50 gsm or less.

[0083] By setting the basis weight to be equal to or higher than the lower limit of the preferable range, the resin material for preform can be sufficiently disposed on the surface of the reinforcing fiber base material, and the laminated reinforcing fiber base materials can be integrated. On the other hand, by setting it to be equal to or lower than the upper limit, it is possible to suppress the inhibition of resin impregnation and the generation of voids during resin injection, and prevent the deterioration of the mechanical properties between layers.

[0084] The resin material for preform according to the reinforcing fiber base material of the present invention is preferably granular. By making it granular, even when the basis weight of the resin material for preform is equal, the bulk height (apparent thickness) of the resin material for preform increases, so that the resin material for preform easily adheres so as to straddle a reinforcing fiber base material adjacent to a certain reinforcing fiber base material in the preform, and a preform excellent in form stability can be obtained.

[0085] When the resin material for preform according to the reinforcing fiber base material of the present invention is granular, the average particle diameter is preferably 50 μm or more and 1000 μm or less.

[0086] By setting the average particle diameter to be equal to or higher than the lower limit of the preferable range, the resin material for preform easily adheres so as to straddle a reinforcing fiber base material adjacent to a certain reinforcing fiber base material, and a preform excellent in form stability can be obtained. On the other hand, by setting it to be equal to or lower than the upper limit, the disturbance of the reinforcing fibers and the voids can be suppressed, and an FRP excellent in mechanical properties can be obtained.

[0087] [Preferred embodiment regarding the melting point of the constituent material of the reinforcing fiber base material] In the reinforcing fiber base material of the present invention, it is preferable that the melting point Tmb (°C) of the resin material for preform is lower than the melting point Tmv (°C) of the nonwoven fabric sheet and the melting point Tms (°C) of the stitch yarn.

[0088] By configuring the melting point Tmb (°C) of the resin material for the preform to be lower than the melting point Tmv (°C) of the nonwoven fabric sheet, in the process of manufacturing a nonwoven fabric sheet with the resin material for the preform fixed to the surface, the resin material for the preform can be firmly fixed to the nonwoven fabric sheet while maintaining the original form of the nonwoven fabric sheet. That is, in the process of heating and melting the resin material for the preform and attaching it to the nonwoven fabric sheet, and then cooling to fix the resin material for the preform to the surface of the nonwoven fabric sheet, by setting the heating temperature to be equal to or higher than Tmb (°C) and equal to or lower than Tmv (°C), the resin material for the preform can be fixed to the nonwoven fabric sheet while maintaining the form of the nonwoven fabric sheet.

[0089] Furthermore, by configuring the melting point Tmb (°C) of the resin material for the preform to be lower than the melting point Tms (°C) of the stitch yarn, in the preform process, the resin material for the preform can be fixed to the adjacent reinforcing fiber base material while maintaining the original form of the reinforcing fiber base material. A preform that is strong and has excellent form stability can be obtained. That is, in the preform process of heating and integrating the laminated reinforcing fiber base materials, by setting the heating temperature to be equal to or higher than Tmb (°C) and equal to or lower than Tms (°C), the stitch yarn does not melt, so the resin material for the preform can be fixed to the adjacent reinforcing fiber base material while maintaining the form of the reinforcing fiber base material.

[0090] [Preferred embodiment related to the method of fixing the stitch yarn] The method for fixing the stitch yarn according to the reinforcing fiber base material of the present invention is preferably a tricot stitch. The tricot stitch weaves the stitch yarn in a zigzag shape to fix the reinforcing fiber yarn. Compared with the chain stitch that weaves the stitch yarn in a straight line, the stitches on the surface of the reinforcing fiber base material face in multiple directions, and the length of the stitch yarn arranged on the surface of the reinforcing fiber base material becomes longer. Therefore, the non-woven fabric sheet can be firmly fixed to the reinforcing fiber base material. As a result, the form stability of the reinforcing fiber base material is improved. Furthermore, in the present invention, since a plurality of reinforcing fiber base materials are laminated and integrated using the resin material for the preform fixed to the non-woven fabric surface, the non-woven fabric is firmly integrated with the reinforcing fiber base material, and thus the form stability of the finally obtained preform is also improved.

[0091] Also, by using the tricot stitch, it is easy to reduce the initial shear rigidity of the reinforcing fiber base material. This is because the orientation direction of the stitches on the surface of the reinforcing fiber base material is less likely to face the shear direction of the reinforcing fiber base material, so the influence of the deformation resistance of the stitch yarn on the increase in the shear deformation resistance of the reinforcing fiber base material can be suppressed.

[0092] The method for fixing the stitch yarn according to the reinforcing fiber base material of the present invention preferably has a gauge length larger than the stitch length. With such a configuration, even when the reinforcing fiber base material is greatly shear-deformed, the orientation direction of the stitches on the surface of the reinforcing fiber base material is less likely to face the shear direction of the reinforcing fiber base material, so it is easy to shape it into a complex shape with a small load.

[0093] The stitch length is preferably in the range of 2 to 10 mm. By setting the stitch length to be equal to or greater than the lower limit, the restraint of the reinforcing fiber yarn by the stitch yarn does not become too strong, so the formability of the reinforcing fiber base material is less likely to be impaired. On the other hand, by setting it to be equal to or less than the upper limit, the restraint of the reinforcing fiber yarn by the stitch yarn does not become too weak, and the form stability of the reinforcing fiber base material is improved.

[0094] [Initial shear rigidity] In the present invention, the initial shear rigidity K (N / mm / gsm) means the resistance when a tensile strain of 2% is applied in the bias extension test, and is represented by Equation 2. K = Fb ÷ h ÷ M ··· (Equation 2)

[0095] However, Fb (N) is the load when a tensile strain of 2% is applied in the bias extension test, h (mm) is the width of the test piece used in the bias extension test, and M (gsm) is the basis weight of the reinforcing fibers of the reinforcing fiber substrate used in the bias extension test.

[0096] Here, the bias extension test measures the displacement and load when a tensile load is applied in the in-plane direction in which the reinforcing fiber substrate can undergo shear deformation. The in-plane direction in which the reinforcing fiber substrate can undergo shear deformation is, when the reinforcing fiber sheet in the reinforcing fiber substrate is oriented in only one axis, the direction at an angle of 45° with the orientation direction of the reinforcing fiber yarn. Also, when the reinforcing fiber sheet in the reinforcing fiber substrate is oriented in two or more axes, it is the direction in which the angle formed with the orientation direction of the reinforcing fibers included in each reinforcing fiber sheet is maximized. For example, in the case of a reinforcing fiber substrate composed of a reinforcing fiber sheet in which the reinforcing fiber yarns are oriented in two directions of 0° (180°) and 90° (270°) respectively, the in-plane directions in which the reinforcing fiber substrate can undergo shear deformation are two directions of 45° and 135°.

[0097] The specific method of the bias extension test is as follows.

[0098] First, a rectangular test piece (length 230 mm × width 90 mm) is prepared so that the in-plane direction in which the reinforcing fiber substrate can undergo shear deformation becomes the longitudinal direction (Figure 4). Clamp both ends of this test piece, 25 mm each, and pull the test piece in the long axis direction with a distance between chucks of 180 mm and a test speed of 20 mm / min, and measure the displacement and load. The test temperature is room temperature (23°C).

[0099] In the bias extension test, as shown in Fig. 5, since the test piece shows non-uniform deformation, it is necessary to note that the measurement results change when the ratio of the width of the test piece, the distance between chucks, and the test speed changes. Therefore, in the present invention, a bias extension test is performed using a test piece of the above dimensions and a test speed.

[0100] In addition, when there are a plurality of in-plane directions in which the reinforcing fiber base material can be shear-deformed, the initial shear rigidity is calculated in each direction, and the largest value is taken as the initial shear rigidity of the reinforcing fiber base material. For example, taking a reinforcing fiber base material in which the reinforcing fiber yarns are oriented in two axial directions of +45° and -45° and the stitching direction (the weaving direction of the reinforcing fiber base material) is the 0° direction as an example, the initial shear rigidity K0 when the reinforcing fiber base material is shear-deformed in the 0° direction and the initial shear rigidity K90 when the reinforcing fiber base material is shear-deformed in the 90° direction can be obtained respectively. At this time, due to the addition of the deformation resistance of the stitch yarn, K0 > K90, so K0 is adopted as the initial shear rigidity.

[0101] The initial shear rigidity can be controlled by the orientation direction of the reinforcing fiber yarns in the reinforcing fiber sheet when the reinforcing fiber base material is used, the stitching pattern of the stitch yarn, and the tension at the time of fixing. In addition, the initial shear rigidity can be controlled by adjusting the type and basis weight of the reinforcing fiber yarns, non-woven fabric sheet, preform resin material, and stitch yarn that make up the reinforcing fiber base material. However, since these are caused by deformation resistance and friction, it is difficult to be less than 1.5×10 -5 N / mm / gsm.

[0102] The smaller the value of the initial shear rigidity, the easier it is for the reinforcing fiber base material to be shear-deformed, which is preferable in terms of formability. On the other hand, conventional reinforcing fiber base materials with a small value of initial shear rigidity often have poor morphological stability. Therefore, as described later, it is important to combine with the preform resin material in an appropriate configuration in order to achieve both formability and morphological stability.

[0103] The initial shear rigidity is 1.5×10 -4It is important that it be below N / mm / gsm. When there is an excess of the reinforcing fiber base material in the process of shaping the product shape, the excess can be diffused around by causing shear deformation without buckling the reinforcing fiber base material in place, and the generation of wrinkles can be suppressed. When the peak load in the bending test described later is appropriately set, the initial shear rigidity is 1.5×10 -4 By setting it to below N / mm / gsm, the shear deformation of the reinforcing fiber base material becomes easy, and the excess of the reinforcing fiber base material can be easily diffused around before the excess buckles, and the generation of wrinkles can be suppressed.

[0104] [Range of peak load in bending test] In the present invention, the peak load P (N / gsm 3 ) in the bending test is a value obtained by normalizing the maximum load generated in the three-point bending test by the basis weight of the reinforcing fiber base material, and is represented by Equation 3. P = Ff÷M 3 ···(Equation 3)

[0105] However, Ff (N) is the maximum load generated in the three-point bending test, and M (gsm) is the basis weight of the reinforcing fiber base material used in the three-point bending test.

[0106] In the present invention, it is important that the range of the peak load in the bending test of the reinforcing fiber base material is 2.7×10 -9 N / gsm 3 or more and 1.4×10 -8 N / gsm 3 or less. When there is an excess of the reinforcing fiber base material in the process of shaping the product shape, the excess can be diffused around by causing shear deformation without buckling the reinforcing fiber base material in place, and the generation of wrinkles can be suppressed. By setting the peak load to 2.7×10 -9 N / gsm 3 or more, stiffness is generated in the reinforcing fiber base material, so the excess of the reinforcing fiber base material is less likely to buckle in place, and the generation of wrinkles can be suppressed. On the other hand, by setting the peak load to 1.4×10 -8 N / gsm 3 or less, the reinforcing fiber base material can be bent and made to conform to the product shape.

[0107] For the loading jig used in the three-point bending test, the loading jig described in JIS K 7074 (1988) is used. That is, the radius of the tip shape of the upper support jig is 5 mm, and the radius of the lower support jig is 2 mm. The distance between the lower jig supports is set to 32 mm for use. The test temperature is room temperature (23 °C).

[0108] The procedure for the three-point bending test is as follows. First, a rectangular test piece (length 100 mm × width 50 mm) is cut out from the reinforced fiber base material to prepare the test piece. At this time, with the stitching direction (the weaving direction of the reinforced fiber base material) as 0°, each test piece is prepared so that the 0°, 45°, 90°, and 135° directions are the longitudinal directions of the test piece. For each of the prepared test pieces, a three-point bending test is performed under the condition of bending so that one surface contacts the upper jig support and under the condition of bending so that the other surface contacts the upper jig support. One test piece is placed at the position where the upper jig support contacts the center of the longitudinal direction of the test piece, the test piece is loaded at a test speed of 2 mm / min, and the maximum load Ff (N) generated in the three-point bending test is measured. This measurement is performed for a total of 8 cases where the front and back surfaces in the 0°, 45°, 90°, and 135° directions contact the upper jig support. The range of the peak load of the bending test is the range from the minimum value to the maximum value of the peak load P of the bending test obtained from the test results of these 8 cases.

[0109] Note that in the three-point bending test, it is necessary to pay attention that the measurement results change when the dimensions of the test piece, the distance between the lower jig supports, or the test speed changes. Therefore, in the present invention, the three-point bending test is performed using the test piece with the above dimensions and the test speed.

[0110] [Preferred embodiment related to the manufacturing method of the reinforced fiber base material] The manufacturing method of the reinforcing fiber base material of the present invention is a method for manufacturing a reinforcing fiber base material in which one or more non-woven fabric-attached reinforcing fiber sheets, in which a non-woven fabric sheet is disposed on one or both surfaces of a reinforcing fiber sheet formed by aligning reinforcing fiber yarns in parallel, are laminated and fixed with a stitch yarn, and (a) a resin material for preform is fixed to at least one outermost surface of the reinforcing fiber base material, (b) after applying a tensile strain of 10% or more in a direction in which shear deformation is applied in the in-plane direction of the reinforcing fiber base material, (c) a tensile strain of 10% or more is applied in a direction different from the direction in which the shear deformation is applied. For convenience, the step of (b) is called the first shear deformation step, and the step of (c) is called the second shear deformation step.

[0111] In the present invention, it is important that a resin material for preform is fixed to at least one outermost surface of the reinforcing fiber base material. As described above, the reinforcing fiber base material is manufactured such that a resin material for preform exists on at least one outermost surface of the reinforcing fiber base material using at least one yarn (fiber) of a stitch yarn, a non-woven fabric sheet, and a reinforcing fiber yarn to which the resin material for preform is fixed in advance. Alternatively, after manufacturing the reinforcing fiber base material, there is a method of spraying a resin material for preform on one of its outermost surfaces.

[0112] [Method for Measuring Tensile Strain] The direction in which shear deformation is applied means the in-plane direction in which the reinforcing fiber base material can be sheared. The tensile strain ε (%) can be expressed as follows in Equation 4 using the length Lfb (m) of the reinforcing fiber base material before deformation and the length Lfa (m) of the reinforcing fiber base material after deformation along the direction in which shear deformation is applied. ε = (Lfa - Lfb) ÷ Lfb × 100 ··· (Equation 4)

[0113] The lengths of the reinforcing fiber base material before and after deformation can be measured with a ruler or the like. Also, as will be described later in the examples, when continuously applying tensile strain using, for example, the speed difference of rolls, the tensile strain (%) can be measured by replacing the downstream nip roll speed (va) and the upstream nip roll speed (vb) with Lfa and Lfb in Equation 4, respectively.

[0114] In the present invention, in the first shear deformation step, it is important to apply a tensile strain of 10% or more in the in-plane direction of the reinforcing fiber base material. By shifting the relative positions of the reinforcing fiber yarns and the stitch yarns, the resin material for preform fixed at positions that become resistant when the reinforcing fiber base material is shear-deformed, that is, between fiber bundles of two or more adjacent reinforcing fiber yarns and between the stitch yarn and the fiber bundle of the reinforcing fiber yarn, can be peeled off.

[0115] Due to local deformation of the resin material for preform, the reinforcing fiber yarns, or the stitch yarns, the resin material for preform fixed at positions that become resistant when the reinforcing fiber base material is shear-deformed may remain, and the formability of the reinforcing fiber base material may not be sufficiently improved, or the deformation of the reinforcing fiber base material may become non-uniform when shaping it into the product shape. By setting the applied tensile strain to 10% or more, such problems can be solved, and a reinforcing fiber base material with excellent formability can be obtained.

[0116] Also, the applied tensile strain is preferably 30% or less. Although it depends on the material of the stitch yarn or non-woven fabric sheet, the fixing method of the stitch yarn, and the orientation direction of the reinforcing fiber yarns, setting the applied tensile strain to 30% or less can suppress breakage of the fibers constituting the stitch yarn or non-woven fabric sheet and maintain the form stability of the reinforcing fiber base material. Furthermore, the applied tensile strain is preferably 20% or less. When the applied tensile strain is 20% or less, it is easy to suppress the disorder and floating of the reinforcing fiber yarns in the subsequent step (the step of applying a tensile strain of 10% or more in a different direction).

[0117] In the present invention, after applying a tensile strain in a predetermined direction (direction A) in the first shear deformation step, it is important to apply a tensile strain in a different direction (direction B) in the second shear deformation step.

[0118] When peeling off the resin material for the preform fixed in the first shear deformation process, since the fixed resin material for the preform is randomly peeled off from the weakly fixed parts, the disorder and lifting of the reinforcing fiber yarns occur unevenly. Therefore, in order to reduce the disorder and lifting of the reinforcing fiber yarns, it is important to apply a shear deformation of 10% or more in a direction different from the first time in the subsequent second shear deformation process.

[0119] From the viewpoint of suppressing the disorder and lifting of the reinforcing fiber yarns, it is preferable to set the magnitude of the tensile strain in the second shear deformation process so that any one of the length, width, and orientation direction of the reinforcing fiber base material returns to the state before the first shear deformation process is performed.

[0120] As a method of applying tensile strain in the longitudinal direction and the width direction, there is a sequential biaxial stretching method in which the reinforcing fiber base material is stretched in the longitudinal direction or the width direction and then stretched in a direction orthogonal to the stretching direction of the previous stage, and any conventionally known tenter stretching method can be adopted.

[0121] As a method of uniaxial stretching in the longitudinal direction, a conventionally known method can be adopted. Examples of the uniaxial stretching method include an in-roll stretching method and a clip tenter method. From the viewpoint of improving operability and reducing equipment costs, the in-roll stretching method is more preferable. The in-roll stretching method is a method in which a plurality of rolls rotated at different rotational speeds are arranged at arbitrary intervals in the longitudinal direction with the upstream-side installed roll at a low speed and the downstream-side installed roll at a high speed, and the reinforcing fiber base material is run through the gap between the rolls to stretch the reinforcing fiber base material according to the roll speed difference. If the stretching distance, which is the arrangement distance of the rolls, is shorter than twice the width of the reinforcing fiber base material, there is a possibility that the application of tensile strain in the longitudinal direction becomes insufficient. The stretching distance can be appropriately set according to the running property of the multilayer film. In order to enhance the holding force of the film on the roll, improve the grip, and further prevent the influence of the stress in the heat stretching process from spreading to the previous and subsequent processes, it is preferable that the roll is provided with a nip mechanism.

[0122] As a method for extending horizontally in the width direction, any conventionally known tenter extension method can be adopted. Examples of the horizontal one-axis extension method include a method in which both end portions in the width direction of an unoriented film are gripped by tenter clips, the distance between the tenter clips in the width direction is gradually increased, and the film is widened and extended in the width direction.

[0123] [Preferred embodiments of the direction for applying shear deformation] In the present invention, it is preferable that the direction (A direction) for applying shear deformation is the stitching direction.

[0124] With such a configuration, the reinforcing fiber base material can be deformed while keeping the distance between adjacent stitch yarns in a direction orthogonal to the stitching direction constant, and when the reinforcing fiber base material is deformed in a direction different from the direction for applying this shear deformation in a subsequent process, the disorder and floating of the reinforcing fiber yarns can be reduced.

[0125] When the direction (A direction) for applying shear deformation is the stitching direction, it is preferable to use a stitch yarn having a large elongation at break. When the elongation at break is large, the stitch yarn is less likely to break when shear deformation is applied, the form of the reinforcing fiber base material is maintained, and the quality of the reinforcing fiber base material can be kept good.

[0126] Also, in the present invention, it is also preferable that the direction (A direction) for applying shear deformation is a direction orthogonal to the stitching direction. This configuration is such that even with a tensile strain of about 10%, the disorder and floating of the reinforcing fiber yarns are likely to occur, but since the tensile strain applied to the stitch yarn is small, the form of the reinforcing fiber base material is maintained, and the quality of the reinforcing fiber base material can be kept good. Further, with such a configuration, a stitch yarn having a small elongation at break can be used, so the degree of freedom in substrate design is increased.

Examples

[0127] The present invention will be further described below with reference to examples. The raw materials and molding methods used in the examples and comparative examples are as follows. Note that the present invention is not limited to these examples and comparative examples.

[0128] <Reinforcing fiber yarn> PAN-based carbon fiber with 24,000 filaments, tensile strength: 6.0 GPa, and tensile modulus: 294 GPa was used.

[0129] <Stitch yarn> An 18-filament, 33 dtex polyester yarn was used as stitch yarn A. The melting point was 260 °C and the elongation at break was 12%.

[0130] Two 4-filament, 23 dtex copolymer polyamide yarns were plied together and used as stitch yarn B. The melting point Tms was 140 °C and the elongation at break was 51%.

[0131] <Resin material for preform> A granular resin material for preform, EP05311 manufactured by Hexion, was used as resin material A for preform. The melting point Tmb was 70 °C and the average particle size was 70 μm.

[0132] <Nonwoven fabric sheet> A resin prepared by adjusting and polymerizing polyamide 6 to 20 mol% and polyamide 12 to 80 mol% was made into a nonwoven fabric by a meltblowing device to obtain a nonwoven fabric sheet A with a width of 1 m. The melting point Tmv was 150 °C, the basis weight was 10 gsm, and the fiber diameter was 40 μm.

[0133] (Example 1) A 1 m-wide reinforcing fiber substrate [1] was produced by the following procedure.

[0134] (1) Nonwoven fabric placement process The nonwoven fabric sheet A was continuously placed on the belt conveyor such that the longitudinal direction of the nonwoven fabric sheet A was parallel to that of the belt conveyor. Such a belt conveyor continued to move at a constant speed (1 m / min in this embodiment) in its longitudinal direction (0° direction) even during the subsequent lamination of the reinforcing fiber sheet and the nonwoven fabric sheet, and continuously conveyed it to the integration process described later.

[0135] (2) Arrangement process of reinforcing fiber yarns (first direction) On the nonwoven fabric sheet A, reinforcing fiber yarns that were horizontally opened and loosened without mixing in untwisting were arranged in parallel at -45° with respect to the longitudinal direction (the direction in which the belt conveyor conveys, 0° direction) and at 240 gsm to form a -45° reinforcing fiber sheet. The arrangement of the reinforcing fiber yarns of the -45° reinforcing fiber sheet was performed by a carriage device. The carriage device in this process reciprocates in the -45° direction, and it is a device that arranges the reinforcing fiber yarns on the belt conveyor when moving forward (or backward) within it. It was controlled so that the reinforcing fiber yarns did not overlap and were arranged adjacent to each other in order in synchronization with the speed at which the belt conveyor was conveying in the longitudinal direction.

[0136] (3) Arrangement process of reinforcing fiber yarns (second direction) A second nonwoven fabric sheet A was placed on the -45° sheet, and on it, reinforcing fiber yarns were arranged in parallel at +45° with respect to the longitudinal direction and at 240 gsm in the same manner as the formation of the -45° sheet to form a +45° reinforcing fiber sheet. As a result, a laminate of (nonwoven fabric sheet A / -45° reinforcing fiber sheet / nonwoven fabric sheet A / +45° reinforcing fiber sheet) was produced.

[0137] (4) Integration process Subsequently, the laminate on the belt conveyor formed as described above was stitched and integrated with stitch thread A. In such stitching, the stitch thread A was unwound by an unwinding device and knitted while passing a needle through the laminate. The fixing method of the stitch thread was chain stitch, with a stitch length of 3 mm and a gauge length of 5 mm. The nonwoven fabric sheet A was excellent in needle penetrability, and the fibers of the nonwoven fabric did not get entangled with the needle.

[0138] (5) Preform resin material spraying process Next, on the surface where the nonwoven fabric sheet of the reinforcing fiber base material was not disposed, the preform resin material A was dropped while being measured to have a mass per unit area of 20 gsm using an embossing roll and a doctor blade, and uniformly dispersed. Subsequently, the preform resin material A was fixed to the surface of the reinforcing fiber base material by passing it under a far-infrared heater set so that the surface temperature of the reinforcing fiber base material became 100°C at a speed of 0.3 m / min, and wound around a roll.

[0139] (6) Preform resin material peeling process The reinforcing fiber base material was unwound from the roll, and a tensile strain of 10% was applied in the longitudinal direction (stitching direction) of the reinforcing fiber base material with the rotation speed ratio (va) / (vb) of the downstream nip roll speed (va) and the upstream nip roll speed (vb) being 1.1, and wound around a roll. At this time, the width of the reinforcing fiber base material had shrunk to 0.9 m. Subsequently, the reinforcing fiber base material was unwound from this roll, and the width of the reinforcing fiber base material was returned to 1 m by uniformly applying a tensile strain of 11% in the width direction (direction orthogonal to the stitching direction) by hand, obtaining the reinforcing fiber base material [1]. When the surface of the reinforcing fiber base material [1] was observed, the surface of the preform resin material was smooth and rounded, being a smooth surface. Also, although the stitch thread was partially broken, the form of the reinforcing fiber base material was maintained.

[0140] (Example 2) Up to the step of spraying the resin material for the preform, the procedure was the same as in Example 1. Subsequently, the reinforcing fiber base material was unwound from the roll and cut into pieces with a width of 1 m and a length of 1 m. Subsequently, a gripping jig with a length of 50 mm was used to grip the end portion in the width direction of the reinforcing fiber base material, and the reinforcing fiber base material was pulled and deformed in the width direction (a direction perpendicular to the stitching direction), increasing the width to 1.1 m. By performing this operation while shifting the gripping portion by 25 mm in the longitudinal direction of the reinforcing fiber base material, a tensile strain of 10% was imparted to the entire reinforcing fiber base material in the width direction (a direction perpendicular to the stitching direction).

[0141] At this time, the reinforcing fiber base material contracted in the stitching direction, and the length decreased to 0.9 m. Also, since the tension of the stitching thread was relaxed, the fiber bundles of the reinforcing fiber yarns lifted up and the fiber orientation was disrupted, but the form of the reinforcing fiber base material was maintained.

[0142] Subsequently, a similar gripping jig was used to grip the end portion in the longitudinal direction (stitching direction) of the reinforcing fiber base material in the longitudinal direction of the reinforcing fiber base material, and the reinforcing fiber base material was pulled and deformed in the longitudinal direction (stitching direction) to restore the length to 1 m. By performing this operation while shifting the gripping portion by 25 mm in the width direction of the reinforcing fiber base material, a tensile strain of 11% was imparted to the entire reinforcing fiber base material in the longitudinal direction (stitching direction).

[0143] At this time, the tension of the stitching thread increased, and the lifting of the fiber bundles of the reinforcing fiber yarns decreased, but the disruption of the fiber orientation remained partially. This reinforcing fiber base material was designated as reinforcing fiber base material [2].

[0144] When the surface of the reinforcing fiber base material [2] was observed, the surface of the resin material for the preform was smooth and rounded, being a smooth surface. Also, no breakage of the stitching thread was confirmed.

[0145] (Example 3) The steps up to the step of spraying the resin material for the preform were carried out in the same manner as in Example 1, except that the first direction was set to 0° and the second direction was set to 90°. Subsequently, this reinforcing fiber base material was unwound from a roll and wound onto another roll. The reinforcing fiber fabric moved intermittently from the unwinding side to the winding side, and the swinging roll was swung during the stop of the intermittent operation to give the reinforcing fiber base material a deformation history with a maximum shear deformation angle in its in-plane direction of 30°. Then, the reinforcing fiber base material was wound onto a roll in a state where the shear deformation angle had returned substantially to 0°, obtaining the reinforcing fiber base material [3].

[0146] When observing the surface of the reinforcing fiber base material [3], the stitch yarn was partially broken, but the form of the reinforcing fiber base material was maintained.

[0147] (Example 4) A 1-m-wide reinforcing fiber base material [4] was produced in the same procedure as in Example 1, except that stitch yarn B was used instead of stitch yarn A.

[0148] When observing the surface of the reinforcing fiber base material [4], the surface of the resin material for the preform was smooth and rounded, being a smooth surface. Also, no breakage of the stitch yarn was confirmed.

[0149] (Example 5) A 1-m-wide reinforcing fiber base material [5] was produced in the same procedure as in Example 2, except that stitch yarn B was used instead of stitch yarn A.

[0150] When observing the surface of the reinforcing fiber base material [5], the surface of the resin material for the preform was smooth and rounded, being a smooth surface. Also, although some disturbance in fiber orientation was confirmed, no breakage of the stitch yarn was confirmed.

[0151] (Example 6) A 1-m-wide reinforcing fiber base material [6] was produced in the same procedure as in Example 3, except that stitch yarn B was used instead of stitch yarn A.

[0152] When observing the surface of the reinforcing fiber base material [6], the surface of the resin material for preform was smooth and rounded, presenting a smooth surface. Also, no breakage of the stitch yarn was confirmed.

[0153] (Reference Example 1) A 1m-wide reference reinforcing fiber base material [1´] was prepared in the same procedure as in Example 1, except that the dispersion amount of the resin material for preform was set to 20 gsm per unit area in the resin material for preform spraying process.

[0154] (Comparative Example 1) A 1m-wide comparative reinforcing fiber base material [1c] was produced by the following procedure.

[0155] (1) Nonwoven fabric placement process The nonwoven fabric sheet A was continuously placed on the belt conveyor such that the longitudinal direction of the nonwoven fabric sheet A was parallel to that of the belt conveyor. Such a belt conveyor continued to move at a constant speed (1 m / min in this example) in its longitudinal direction (0° direction) during the subsequent lamination of the reinforcing fiber sheet and the nonwoven fabric sheet, and continuously conveyed to the integration process described later.

[0156] (2) Reinforcing fiber yarn placement process (first direction) On the nonwoven fabric sheet A, the reinforcing fiber yarns that were cross-opened without adding untwisting were arranged in parallel at -45° with respect to the longitudinal direction (the direction in which the belt conveyor conveys, 0° direction) and at a density of 240 gsm to form a -45° reinforcing fiber sheet. The arrangement of the reinforcing fiber yarns of the -45° reinforcing fiber sheet was performed by a carriage device. The carriage device in this process reciprocates in the -45° direction, and when moving forward (or backward) within it, it is a device for placing the reinforcing fiber yarns on the belt conveyor, and it was controlled so that the reinforcing fiber yarns did not overlap and were arranged adjacent to each other in order in synchronization with the speed at which the belt conveyor was conveying in the longitudinal direction.

[0157] (3) Reinforcing fiber yarn placement process (second direction) Place the second non-woven fabric sheet A on the -45° sheet, and on top of it, the -45° sheet In the same manner as the formation, the reinforcing fiber yarns were arranged in parallel at +45° with respect to the longitudinal direction and at 240 gsm to form a +45° reinforcing fiber sheet. As a result, a laminate of (non-woven fabric sheet A / -45° reinforcing fiber sheet / non-woven fabric sheet A / +45° reinforcing fiber sheet) was produced.

[0158] (4) Integration process Subsequently, the laminate on the belt conveyor formed as described above was stitched with stitch yarn A to be integrated, resulting in a comparative reinforcing fiber base material [1c]. In such stitching, the stitch yarn A was unwound by an unwinding device and knitted while passing the needle through the laminate. The fixing method of the stitch yarn was chain stitch, with a stitch length of 3 mm and a gauge length of 5 mm. The non-woven fabric sheet A was excellent in needle penetrability, and the fibers of the non-woven fabric did not get entangled with the needle.

[0159] (Comparative Example 2) With the first direction being 0° and the second direction being 90°, a 1 m-wide reinforcing fiber base material [2c] was produced in the same procedure as Comparative Example 1, except that the fixing method of the stitch yarn was tricot knitting.

[0160] (Comparative Example 3) On the surface of the comparative reinforcing fiber base material [1c] where the non-woven fabric was not arranged, the resin material A for preform was dropped while being metered to a mass of 20 gsm per unit area using an embossing roll and a doctor blade, and uniformly dispersed. Subsequently, the resin material A for preform was fixed onto the comparative reinforcing fiber base material [1c] by passing it under a far-infrared heater set so that the surface temperature of the reinforcing fiber base material was 100°C at a speed of 0.3 m / min, producing a comparative reinforcing fiber base material [3c] with the resin material A for preform fixed to the reinforcing fibers.

[0161] (Comparative Example 4) A comparative reinforcing fiber base material [4c] was produced in the same procedure as Comparative Example 3, except that the comparative reinforcing fiber base material [1c] was used as the comparative reinforcing fiber base material [2c].

[0162] ≪Evaluation Method≫ As described above, morphological stability is required for the lamination process and the conveyance process, and formability is required for the preform process. The process passability in each process can be clarified by evaluating (i) lamination workability, (ii) formability of complex shapes (wrinkles), (iii) formability of complex shapes (bulges), (iv) formability of complex shapes (stitch breakage), and (v) preform conveyance property. Therefore, using the reinforced fiber base materials created in the examples and comparative examples, these were evaluated and compared. The results of the examples were summarized in Table 1, and the results of the comparative examples were summarized in Table 2.

[0163] The characteristic evaluation method of the reinforced fiber base material and the evaluation methods of the above (i) to (v) are shown below.

[0164] (Initial shear rigidity of the reinforced fiber base material) Three test pieces were cut out for all in-plane directions in which the reinforced fiber base material can be shear-deformed so that the end of the nonwoven fabric sheet is not included in each reinforced fiber base material, and a bias extension test was performed to obtain the average value of the initial shear rigidity K.

[0165] (Bending characteristics) Six test pieces were cut out from each reinforced fiber base material so that the end of the nonwoven fabric sheet was not included, with 0°, 45°, 90°, and 135° in the longitudinal direction, and a three-point bending test was performed three times under the condition of bending so that one surface and the other surface each contacted the upper jig fulcrum, and the average value of the peak load P of each of the eight bending tests was obtained, and the minimum value and the maximum value among these were obtained.

[0166] (Lamination workability) One test piece with a length of 1000 mm and a width of 300 mm was cut out from each reinforced fiber base material so that the end of the nonwoven fabric sheet was not included, with 0° and 45° in the longitudinal direction. Subsequently, two test pieces were laminated so that the entire pieces overlapped to form a laminate. At this time, when the longitudinal direction of the laminate was 0°, the reinforcing fiber yarn orientation directions of each reinforced fiber sheet were laminated so as to be -45°, 45°, 0°, and 90° from the lower surface. That is, the lamination structure of the laminate is [-45° / 45° / 0° / 90°].

[0167] In this series of operations, the lamination workability was evaluated in the following five steps shown as A to E, and a grade of C or above was considered passing. A: There is no change in the projected area of the reinforcing fiber base material before and after lamination, and there is no change in the stitch length and gauge length in all the reinforcing fiber base materials. B: There is no change in the projected area of the reinforcing fiber base material before and after lamination, but there is a change in either the stitch length or the gauge length in one reinforcing fiber sheet. C: There is no change in the projected area of the reinforcing fiber base material before and after lamination, but there is a change in either the stitch length or the gauge length in two reinforcing fiber sheets. D: There is a change in the projected area of the reinforcing fiber base material before and after lamination, and there is a change in either the stitch length or the gauge length in one reinforcing fiber sheet. E: There is a change in the projected area of the reinforcing fiber base material before and after lamination, and there is a change in either the stitch length or the gauge length in two reinforcing fiber sheets.

[0168] Note that the projected area is the value obtained by multiplying the length and width of the reinforcing fiber base material, and the length and width of the reinforcing fiber base material are measured to the nearest 0.1 mm using a ruler. No change in the projected area means no change of 0.5% or more. Also, for the stitch length and gauge length, for the stitch thread passing through the center of the reinforcing fiber base material on one side of the reinforcing fiber base material, the length of 50 repeating units (round down if less than 50 repeating units) from one end to the other end of the reinforcing fiber base material is measured to the nearest 0.1 mm using a ruler, and it means that there is no change of 0.5% or more in all the measured values.

[0169] (Complex shape formability) Using the aluminum shaping jig shown in Fig. 7 with a length of 1100 mm, a width of 90 mm, and a height (depth direction of the paper surface in Fig. 7) of 70 mm, the formability of the reinforcing fiber base material into a complex shape was evaluated. The shaping jig is installed on a metal table (length 2000 mm, width 1000 mm) not shown in the figure, and the metal table has an exhaust port that can be opened and closed at a position where it does not interfere with the shaping jig or the laminate. Subsequently, the laminate whose lamination workability was evaluated was arranged in the shape of the shaping jig in the positional relationship shown in Fig. 8. At this time, a part of the laminate extended from the upper surface of the shaping jig to the surroundings and sagged downward due to its own weight. Further, as shown in Fig. 9, the shaping jig 12 and the laminate 80 were covered with a thermoplastic film 90 (elongation at break 500%, thickness 37.5 μm), and the outer periphery of the thermoplastic film 90 was fixed to the metal table using Solvay's tacky tape SM5126. Subsequently, the air inside was exhausted from the exhaust port of the metal table using a vacuum pump, and the laminate 80 was made to follow the shaping jig 12 by utilizing the force of the thermoplastic film 90 along the shaping jig 12. When the exhaust was completed, the vacuum pressure was -0.1 MPa in gauge pressure.

[0170] Regarding the wrinkles in this series of shaping, the number of wrinkles generated and the length and height of the maximum wrinkle were recorded. Note that the dimensions of the wrinkles were measured using a non-contact three-dimensional measuring machine ATOS manufactured by Zeiss while the vacuum pressure was applied, and values less than 1 mm were rounded up. Further, regarding the ease of following the base material, when the base material followed the concave part which is the boundary between the shaping jig and the metallic table, it was designated as A, when a slight bulge occurred, it was designated as B, and when a bulge of medium degree or more that affected injection molding occurred, it was designated as C, and A or above was considered to be qualified. Also, the number of broken stitch threads on both the thermoplastic film side and the shaping jig side of the preform was recorded.

[0171] (Preform transportability) Regarding the formed laminate, while continuing evacuation, it was put into an oven heated to 110 °C together with the metal table, taken out of the oven 10 minutes after the surface temperature of the aluminum forming jig reached 100 °C, and cooled at room temperature. By this operation, the laminate was fixed and integrated with the preform resin material to obtain a preform. Then, the thermoplastic film was peeled off, the preform was removed from the forming jig, and it was carried to an injection molding apparatus 10 m away while holding both ends in the longitudinal direction by hand. In this series of conveying operations, the lamination workability was evaluated in five stages shown in A to E below, and a grade of C or higher was considered a pass. A: After conveyance, all the interlayers of the reinforcing fiber sheets constituting the laminate are firmly adhered over the entire surface, and no partial peeling is observed. B: After conveyance, all the interlayers of the reinforcing fiber sheets constituting the laminate are firmly adhered over the entire surface, but partial peeling is observed in one interlayer. C: After conveyance, all the interlayers of the reinforcing fiber sheets constituting the laminate are firmly adhered over the entire surface, but partial peeling is observed in two or more interlayers. D: After conveyance, large peeling occurred in any of the interlayers of the reinforcing fiber sheets constituting the laminate. E: The reinforcing fiber base material became scattered and could not be handled as a preform.

[0172] As a result of the above evaluation, the reinforcing fiber base materials [1] to [6] shown in the examples exhibited excellent formability and morphological stability, so they had excellent lamination workability, did not cause wrinkles or bulges even when forming into complex shapes, and also had excellent transportability of the preform. The manufactured preforms with complex shapes were of high quality and high precision without cuts on the final product surface. Furthermore, among them, the reinforcing fiber base materials [4] and [6] shown in Examples 5 and 6 were reinforcing fiber base materials that could obtain preforms with particularly excellent quality without any disturbance of the reinforcing fiber yarns and without stitch breakage when forming into complex shapes.

[0173] In addition, the reinforced fiber base material shown in the reference example [1'] was excellent in lamination workability, and did not cause wrinkles or bulges even when forming into a complex shape, and exhibited excellent formability. However, the ratio of the surface of the nonwoven fabric sheet coated with the resin material for preform was smaller than that of other examples, and the reinforced fiber base material was partially peeled off during preform conveyance, causing disorder in the reinforced fiber yarns.

[0174] On the other hand, the comparative reinforced fiber base materials [1c] and [2c] shown in Comparative Examples 1 and 2 did not cause wrinkles or bulges when forming into a complex shape because they did not have a resin material for preform, but were inferior in lamination workability and caused disorder in the reinforced fiber yarns. Furthermore, they could not maintain the three-dimensional shape of the preform. In addition, the comparative reinforced fiber base materials [3c] and [4c] shown in Comparative Examples 3 and 4 had their base material forms maintained by the resin material for preform and were excellent in lamination workability. However, they had large wrinkles when forming into a complex shape and also had bulges, resulting in inferior formability.

[0175]

Table 1

[0176]

Table 2

Industrial Applicability

[0177] The reinforced fiber base material of the present invention can be suitably used for large members for aircraft, automobiles, ships, etc., and members for general industrial applications such as wind turbine blades.

Explanation of Reference Signs

[0178] Y Reinforced fiber yarn Yg Between fiber bundles of two or more adjacent reinforced fiber yarns 1 Reinforced fiber sheet (0 degrees) 2 Reinforced fiber sheet (+45 degrees) 3 Reinforced fiber sheet (90 degrees) 4 Reinforced fiber sheet (-45 degrees) A nonwoven sheet disposed on the surface of a 5A reinforcing fiber substrate A nonwoven sheet disposed between layers of a 5B reinforcing fiber substrate 51 Fibers constituting the nonwoven sheet 6 Stitch thread 61 Portion where the stitch thread penetrates the reinforcing fiber substrate 7 Needle 8 Reinforcing fiber substrate 9 Resin material for preform 10 Specimen for bias extension test 11 Chuck 12 Shaping jig 80 Laminate 90 Thermoplastic film

Claims

1. A reinforced fiber base material obtained by laminating one or more sheets of a reinforced fiber sheet with a nonwoven fabric sheet having a nonwoven fabric sheet disposed on one or both surfaces of a reinforced fiber sheet formed by aligning reinforcing fiber yarns in parallel and fixing them with stitch yarns, wherein (a) a resin material for preform is fixed to at least one of the surface of the stitch yarn, the entire surface of the fibers constituting the nonwoven fabric sheet, or the surface of the fiber-reinforced yarn, and (b) the resin material for preform is not fixed across between fiber bundles of two or more adjacent reinforcing fiber yarns and between the stitch yarn and the fiber bundle of the reinforcing fiber yarn. (c) The initial shear rigidity is 1.5×10 －５ N / mm / gsm or more and 1.5×10 －４ N / mm / gsm or less, and (d) The range of the peak load in the bending test is 2.7×10 －９ N / gsm ３ or more and 1.4×10 －８ N / gsm ３ or less. A reinforced fiber base material, characterized in that it is as described above.

2. The reinforced fiber base material according to claim 1, characterized in that the basis weight of the nonwoven fabric sheet is 1 gsm or more and 50 gsm or less.

3. The reinforced fiber base material according to claim 1, characterized in that the average fiber diameter of the nonwoven fabric sheet is 1 μm or more and 100 μm or less.

4. The reinforced fiber base material according to claim 1, characterized in that the surface of the resin material for preform fixed to the nonwoven fabric sheet is a smooth surface.

5. The reinforced fiber base material according to claim 1, characterized in that 50% or more and 100% or less of the surface of the nonwoven fabric sheet is covered with a resin material for preform.

6. The reinforced fiber base material according to claim 1, characterized in that 50% or more and 100% or less of the surface of the reinforced fiber sheet is covered with a resin material for preform.

7. The reinforced fiber base material according to claim 1, characterized in that the basis weight of the resin material for preform is 3 gsm or more and 50 gsm or less.

8. The reinforced fiber base material according to claim 1, characterized in that the resin material for preform is in granular form.

9. The reinforced fiber base material according to claim 8, characterized in that the average particle diameter of the resin material for preform is 50 μm or more and 1000 μm or less.

10. The reinforced fiber base material according to claim 1, characterized in that the breaking elongation of the stitch yarn is 15% or more.

11. The reinforced fiber base material according to claim 1, characterized in that the melting point Tmb (°C) of the resin material for preform is lower than the melting point Tmv (°C) of the nonwoven fabric sheet and the melting point Tms (°C) of the stitch yarn.

12. The reinforced fiber base material according to claim 1, characterized in that the fixing method of the stitch yarn is tricot knitting.

13. Among the plurality of laminated reinforced fiber sheets with nonwoven fabric, a first-direction reinforced fiber sheet in which the alignment direction of the reinforced fiber yarns is the first direction and a second-direction reinforced fiber sheet in which the alignment direction of the reinforced fiber yarns is the second direction are included, and the first direction and the second direction are orthogonal to each other. The reinforced fiber base material according to claim 1, characterized in that.

14. A method for manufacturing a reinforced fiber base material, in which one or more reinforced fiber sheets with nonwoven fabric, in which a nonwoven fabric sheet is disposed on one or both surfaces of a reinforced fiber sheet formed by aligning reinforced fiber yarns in parallel, are laminated and fixed with a stitching thread, (a) Fixing a resin material for preform to at least one outermost surface of the reinforced fiber base material, (b) After applying a tensile strain of 10% or more in the direction (A direction) of applying shear deformation in the in-plane direction of the reinforced fiber base material, (c) A tensile strain of 10% or more is applied in a direction (B direction) different from the direction (A direction) of applying the shear deformation. A method for manufacturing a reinforced fiber base material.

15. The method for manufacturing a reinforced fiber base material according to claim 14, characterized in that the direction (A direction) of applying the shear deformation is the stitching direction.

16. The method for manufacturing a reinforced fiber base material according to claim 14, characterized in that the direction (A direction) of applying the shear deformation is a direction orthogonal to the stitching direction.

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