Reinforcing fiber substrate

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 final product surface even in a complicated shape.SOLUTION: There is provided a reinforcing fiber substrate obtained by fixing a nonwoven fabric sheet with a stitching thread on one surface or both surfaces of a reinforcing fiber sheet formed by aligning a reinforcing fiber thread in parallel, wherein (a) the nonwoven fabric sheet is disposed on the outermost surface of at least one of the reinforced fiber substrate, (b) a resin material for a preform is adhered to at least one of the surface of the stitching yarns exposed to the outermost surface of the reinforcing fiber substrate on which the nonwoven sheet is disposed, the entire surface of fibers constituting the nonwoven sheet disposed on the outermost surface of the reinforcing fiber substrate or the surface of the fiber reinforcing yarn strips facing the nonwoven sheet disposed on the outermost surface of the reinforcing fiber substrate, and the reinforcing fiber substrate has (c) an initial shear stiffness in a specific range and (d) 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. More specifically, the present invention relates to a reinforced fiber base material that is excellent in formability and form stability, and can stably produce a high-quality and high-precision preform without cuts on the final product surface even with a complex shape.

Background Art

[0002] Fiber Reinforced Plastics (FRP) in which reinforcing fibers are impregnated with a matrix resin are widely used in aerospace, automotive applications, etc. because of their lightweight and high-strength characteristics. As a molding method that combines the 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 to impregnate and solidify the matrix resin later 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 and triaxial is proposed. A reinforced fiber base material that is penetrated and stitched integrally in the thickness direction of the laminate with a stitch thread. 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. However, since it is necessary to reduce the viscosity of the matrix resin, the mechanical properties may not be fully exhibited as compared with FRP formed from the high-viscosity matrix resin used for prepregs. 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 disposing the nonwoven sheet between layers, it is possible to improve the mechanical properties in the compression after impact (CAI) test generally used to characterize the impact resistance of the structure.

[0005] In the injection molding method for products having a three-dimensional shape, a preform obtained by previously shaping and fixing an integrated laminate of a reinforcing fiber base material into the product shape may be used. The manufacturing process of the preform is divided into a lamination process of laminating reinforcing fiber base materials cut into 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 preforms, a reinforcing fiber base material with a preform resin material pre-fixed on the surface is generally used. Patent Document 1 exemplifies a multi-layer 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 formability and handleability have been proposed by specifying 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 the 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 the preform that adheres 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 cause 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 the preform is not used, although the formability of the reinforced fiber base material is relatively excellent, its morphological 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 reinforced fiber base material with cuts made in the reinforced fiber base material as described in Patent Document 2, although a product with a smooth surface can be obtained, there are cases where the mechanical properties deteriorate due to the discontinuity of the reinforcing fibers, or cases where the appearance quality is impaired because the cuts can be visually recognized from the product surface.

[0013] In addition, for the reinforced fiber base material obtained by peeling off the resin material for the fixed preform as described in Patent Document 3, not only is an apparatus and a process for peeling off the resin material for the preform required, resulting in high costs, but there are also cases where the reinforcing fibers are disturbed or the stitch yarns are cut when peeling off the resin material for the preform.

[0014] Furthermore, simply arranging the composite nonwoven fabric sheet as described in Patent Document 4 between the layers of the reinforced fiber base material cannot be used for stabilizing the form of the reinforced fiber base material or the preform, 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.

[0015] Furthermore, since the conventional reinforced fiber base material with relatively excellent formability is soft and lacks firmness, the surplus of the reinforced fiber base material generated in the process of shaping the product shape buckles on the spot, resulting in a large number of small wrinkles, or there are cases where the reinforcing fibers are disturbed. This problem is particularly prominent in the reinforced fiber base material that does not use the resin material for the preform. On the other hand, although the conventional reinforced fiber base material with poor formability is excellent in form stability, as described above, it has a large deformation resistance and may generate large wrinkles during preform formation. This problem is particularly prominent in a process where the load that can be applied to the reinforced fiber base material during the shaping process is small, or when the load is partially small.

[0016] Thus, in the prior art as described above, it has been extremely difficult to obtain a reinforced 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 that can stably manufacture a high-quality and high-precision preform with excellent formability and form stability, having no cuts on the final product surface even for complex shapes.

Means for Solving the Problems

[0018] As a result of investigations to solve the above problems, the present inventors have found that by limiting the fixing position of the resin material for the preform and giving an original balance to the initial in-plane shear load of the base material and the peak load in the bending test, it is possible to prevent the occurrence of wrinkles even in a process where the load that can be applied to the reinforced fiber base material is small. 〔1〕A reinforced fiber base material in which a non-woven fabric sheet is fixed with a stitch thread on one or both surfaces of a reinforced fiber sheet formed by aligning reinforced fiber yarns in parallel, (a) The non-woven fabric sheet is disposed on at least one outermost surface of the reinforced fiber base material, (b) the surface of the stitch thread exposed on the outermost surface of the reinforced fiber base material where the non-woven fabric sheet is disposed, the entire surface of the fibers constituting the non-woven fabric sheet disposed on the outermost surface of the reinforced fiber base material, or the surface of the fiber-reinforced yarn facing the non-woven fabric sheet disposed on the outermost surface of the reinforced fiber base material, and at least one of them is fixed with a resin material for the preform, (c) The initial shear rigidity is 1.5×10 -5 N / mm / gsm or more and 2.1×10 -4 N / mm / gsm or less, (d) The peak load in the bending test is 2.7×10 -9 N / gsm or more and 8.1×10 -9 N / gsm 3 or less. The reinforced fiber base material is characterized by the above. 〔2〕The reinforced fiber base material according to 〔1〕, characterized in that the basis weight of the non-woven fabric sheet is 10 gsm or more and 50 gsm or less. 〔3〕The reinforced fiber base material according to 〔1〕, characterized in that the average fiber diameter of the non-woven fabric sheet is 1 μm or more and 100 μm or less. 〔4〕The reinforcing fiber base material according to 〔1〕, wherein the surface of the resin material for the preform fixed to the non-woven fabric sheet is a smooth surface. 〔5〕The reinforcing fiber base material according to 〔1〕, wherein 50% or more and 100% or less of the surface of the non-woven fabric sheet is coated with the resin material for the preform. 〔6〕The reinforcing fiber base material according to 〔1〕, wherein the basis weight of the resin material for the preform is 3 gsm or more and 50 gsm or less. 〔7〕The reinforcing fiber base material according to 〔1〕, wherein the resin material for the preform is in granular form. 〔8〕The reinforcing fiber base material according to 〔7〕, wherein the average particle diameter of the resin material for the preform is 50 μm or more and 1000 μm or less. 〔9〕The reinforcing fiber base material according to 〔1〕, wherein the melting point Tmb (°C) of the resin material for the preform is lower than the melting point Tmv (°C) of the non-woven fabric sheet and the melting point Tms (°C) of the stitch yarn. 〔10〕The reinforcing fiber base material according to 〔1〕, wherein the fixing method of the stitch yarn is tricot knitting. 〔11〕Among a plurality of laminated reinforced fiber sheets obtained by fixing the non-woven fabric sheet, a first-direction reinforced fiber sheet in which the alignment direction of the reinforcing fiber yarns is the first direction and a second-direction reinforced fiber sheet in which the alignment direction of the reinforcing fiber yarns is the second direction are included, and the first direction and the second direction are orthogonal to each other. The reinforcing fiber base material according to 〔1〕.

Advantages of the Invention

[0019] According to the present invention, a reinforcing 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 is particularly less likely to generate wrinkles even in a process where the load that can be applied to the reinforcing fiber base material is small 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

Mode for Carrying Out the Invention

[0021] The reinforced fiber base material of the present invention is a reinforced fiber base material in which a non-woven fabric sheet is fixed with a stitch thread on one or both surfaces of a reinforced fiber sheet formed by aligning reinforced fiber yarns in parallel, (a) the non-woven fabric sheet is disposed on at least one outermost surface of the reinforced fiber base material, (b) the surface of the stitch thread exposed on the outermost surface of the reinforced fiber base material on which the non-woven fabric sheet is disposed, the entire surface of the fibers constituting the non-woven fabric sheet disposed on the outermost surface of the reinforced fiber base material, or the surface of the fiber-reinforced yarn facing the non-woven fabric sheet disposed on the outermost surface of the reinforced fiber base material, at least one of which has a resin material for preform fixed thereto, (c) the initial shear rigidity is 1.5×10 -5 N / mm / gsm or more and 2.1×10 -4 N / mm / gsm or less, and (d) the peak load in the bending test is 2.7×10 -9 N / gsm 3 or more and 8.1×10 -9 N / gsm 3It is characterized by the following.

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

[0023] [Outline 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 (weaving 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. In the present invention, the fiber bundle of the reinforced fiber yarn refers to a bundle of reinforced fiber yarns oriented in one direction, which is divided by the stitch yarn for fixing the reinforced fiber substrate.

[0026] Since the reinforced fiber sheet according to the present invention can obtain excellent mechanical properties, it is preferably in a form composed of continuous fiber reinforced fiber yarns.

[0027] Examples of the reinforced fiber yarn include carbon fiber, glass fiber, aramid fiber, alumina fiber, silicon carbide fiber, boron fiber, silicon carbide fiber, etc. 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 obtained 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 achieving both 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, a composite material having mechanical properties such as high rigidity, high tensile strength, and high compressive strength can be obtained. Therefore, 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. Further, 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] [Non-woven 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 joined together by alternating current, and / or heat fusion, and / or adhesion.

[0033] In FIG. 2, the present 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. Also, it is important that the nonwoven fabric sheet is disposed on at least one outermost surface of the reinforcing fiber base material.

[0034] Note that, as described above, the "surface of the nonwoven fabric sheet" means the surface of all the fibers constituting the nonwoven fabric sheet.

[0035] In 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 the preform, but in terms of improving the form stability when formed into a preform, it is preferable to fix the resin material 9 for the preform.

[0036] As the fibers constituting the nonwoven fabric sheet related to the reinforcing fiber base material of the present invention, for example, synthetic fibers can be used, but any material may be used as long as the resin material for the preform can be fixed to the surface and the mechanical properties in the compression after impact (CAI) test can be improved.

[0037] 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 after being mixed 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.

[0038] Also, from the viewpoint of forming a highly tough layer between the layers of the FRP and enhancing the mechanical properties (especially CAI), the synthetic fiber used as the stitch yarn is preferably a copolymer polyamide containing at least two polyamide components selected from polyamide 6, polyamide 6-6, polyamide 6-10, polyamide 12, and polyamide 6-I.

[0039] Also, from the viewpoint of suppressing the decrease in mechanical properties of the FRP under wet heat 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 the resin material that can copolymerize 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, and polyamide 6-6 / 6-T / 6-I. Particularly preferred examples include polyamide 6, polyamide 6-6, polyamide 6-10, polyamide 12, and polyamide 6-I. Furthermore, it is also suitable to use these synthetic fibers as a mixture according to the required properties such as processability, heat resistance, and toughness.

[0040] The nonwoven sheet according to the reinforcing fiber base material of the present invention preferably has a basis weight of 10 gsm or more and 50 gsm or less. Note that gsm is equal to g / m 2 2.

[0041] By increasing the basis weight to 10 gsm or more, the amount of the resin material for preform fixed to the nonwoven sheet increases, and the nonwoven sheet and the reinforcing fiber yarns are easily fixed with the resin material for preform. When the nonwoven sheet and the reinforcing fiber yarns are fixed with the resin material for preform, even when the reinforcing fiber base material is formed into a complex shape, the nonwoven fabric can be deformed while being evenly arranged on the reinforcing fiber yarns, so that a decrease in the mechanical properties between layers can be prevented. On the other hand, by setting it to 50 gsm or less, the burial and impregnation of the resin material for preform into the nonwoven sheet can be suppressed, so that the peeling of the reinforcing fiber base material from the preform can be prevented.

[0042] More preferably, the nonwoven sheet according to the reinforcing fiber base material of the present invention has a basis weight of 10 gsm or more and 20 gsm or less. By setting the basis weight to 10 gsm or more and 20 gsm or less, the interlayer toughness, strength, and elastic modulus can be improved in a well-balanced manner. In addition, by setting it to 10 gsm or more, the local variation in the basis weight of the nonwoven 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 sheet becomes thin, so that the proportion of the reinforcing fibers contained in the FRP increases, and an FRP having excellent mechanical properties can be obtained.

[0043] Preferably, the nonwoven sheet according to the reinforcing fiber base material of the present invention has an average fiber diameter of the fibers constituting the nonwoven sheet of 1 μm or more and 100 μm or less.

[0044] By setting the average fiber diameter to 1 μm or more, it becomes easy to fix the resin material for preform to the nonwoven surface. On the other hand, by setting it to 100 μm or less, the fiber diameter becomes thin, so that even when the basis weight of the nonwoven sheet is small, the surface area increases, and the amount of the resin material for preform fixed can be increased.

[0045] The nonwoven fabric sheet according to the reinforcing fiber base material of the present invention preferably has an average fiber diameter of 5 μm or more and less than 80 μm, more preferably 10 μm or more and less than 60 μm. When the average fiber diameter is within the above preferred range, the flow resistance is small, resin impregnation inhibition and void generation during resin injection can be suppressed, and on the other hand, the thickness between layers when made into FRP becomes small, so the proportion of reinforcing fibers contained in the FRP increases, and an FRP with excellent mechanical properties can be obtained.

[0046] [Reinforcing fiber sheet with nonwoven fabric sheet fixed] The reinforcing fiber sheet with the nonwoven fabric sheet according to the reinforcing fiber base material of the present invention fixed thereto is one in which the nonwoven fabric sheet is disposed on one or both sides of the reinforcing fiber sheet.

[0047] At this time, when a plurality of reinforcing fiber sheets in which the nonwoven fabric sheet is disposed on one side of the reinforcing fiber sheet are laminated, one nonwoven fabric sheet is disposed between adjacent layers of the reinforcing fiber sheets. On the other hand, when a plurality of reinforcing fiber sheets in which the nonwoven fabric sheet is disposed on both sides of the reinforcing fiber sheet are laminated, two nonwoven fabric sheets are disposed between adjacent layers of the reinforcing fiber sheets.

[0048] Since the nonwoven fabric sheet can halve the arrangement process and simplify the manufacturing apparatus and process, it is preferable that the nonwoven fabric sheet is disposed on one side of the reinforcing fiber sheet.

[0049] 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 a plurality of laminated reinforcing fiber sheets with the nonwoven fabric sheet fixed thereto, and it is preferable that the first direction and the second direction are orthogonal to each other.

[0050] By making the first direction and the second direction orthogonal, the reinforcing fiber base material can be sheared and deformed to the same extent in a plurality of in-plane directions that can be sheared. Therefore, even when shaping a laminate reinforced in a plurality of directions by 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 shaping is easy.

[0051] From the viewpoint of simplifying the laminating operation, among a plurality of laminated reinforcing fiber sheets with nonwoven fabric sheets fixed, it is preferable that the alignment direction of the reinforcing fiber yarns is three or more directions. Among them, for example, as [(0° / 90°) / (+45° / -45°)], while making the alignment direction of the reinforcing fiber yarns orthogonal, increasing the orientation direction of the reinforcing fiber yarns enables a configuration that reinforces in a plurality of directions and is also rich in formability. Since such a reinforcing fiber base material has a plurality of reinforcing directions in one sheet, there is an advantage that the laminating operation is simplified and FRP can be obtained at low cost.

[0052] 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 the nonwoven fabric sheet fixed is only the first / second direction. Such a reinforcing fiber base material with the alignment direction of the reinforcing fiber yarns being biaxial is easier to shear and deform and has excellent formability compared to triaxial or quadraxial base materials, and it is easy to reduce the initial shear rigidity.

[0053] [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 is only necessary to be able to be used for fixing the reinforcing fiber sheet and the nonwoven fabric sheet, and the material is not particularly limited.

[0054] When synthetic fibers are used as the stitch yarn, the material can be the same as the synthetic fibers used for the nonwoven fabric sheet.

[0055] In addition, from the viewpoint of improving the morphological stability of the reinforcing fiber base material, when using synthetic fibers as the stitch yarn, it is preferably a copolymerized polyamide 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 base material undergoes shear deformation, a tensile load may be applied to the stitch yarn. However, with the above-described configuration, even when a certain tensile load is applied, the stitch yarn is less likely to plastically deform and break, and the form as the reinforcing fiber base material can be maintained even when the reinforcing fiber base material is formed into a complex shape.

[0056] Also, similar to the nonwoven fabric sheet, from the viewpoint of suppressing the deterioration of the mechanical properties of FRP under wet heat 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, and it is also preferable to use these synthetic fibers as a mixture according to the required properties such as processability, heat resistance, and toughness.

[0057] 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 preferable range, while reducing the cross-sectional area of the stitch yarn, the deformation resistance in the longitudinal direction is appropriately maintained. As a result, the initial shear rigidity of the reinforcing fiber base material can be reduced while firmly maintaining the fixation between the reinforcing fiber sheet and the nonwoven fabric, and furthermore, the meandering of the reinforcing fiber yarn when the reinforcing fiber base materials are laminated can be suppressed, thereby improving the mechanical properties.

[0058] For the same reason as the fiber diameter, the fineness of the stitch yarn for the reinforced 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.

[0059] 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).

[0060] Here, the breaking elongation of the stitch yarn is a value obtained by measuring in accordance with "Single Yarn Tensile Strength and Elongation Rate" of JIS L1095 (2010) as follows, and the elongation rate at the time of single yarn breakage is defined as the breaking elongation.

[0061] 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 reinforced fiber base material is greatly deformed, the stitch does not break, so that the reinforcing fibers can be preferably arranged along the shape. Further, by setting the breaking elongation of the stitch yarn to 30% or more, even when the reinforced fiber base material is locally greatly deformed, the stitch does not break, so that the form of the sheet can be maintained.

[0062] [Resin Material for Preform] In the reinforced 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 but have the property of melting or softening by heat.

[0063] 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 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.

[0064] 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. As the fixing location, 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 can be selected. 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.

[0065] In the reinforcing fiber base material of the present invention, it is important that the resin material for the preform is fixed to at least one of the surface of the stitch yarn exposed on the outermost surface of the reinforcing fiber base material where the non-woven fabric sheet is disposed, the entire surface of the fibers constituting the non-woven fabric sheet disposed on the outermost surface of the reinforcing fiber base material, or the surface of the fiber-reinforced yarn facing the non-woven fabric sheet disposed on the outermost surface of the reinforcing fiber base material.

[0066] As described above, the resin material for preform according to the reinforcing fiber base material of the present invention adheres to at least one of the surface of the stitch yarn exposed on the outermost surface of the reinforcing 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 reinforcing fiber base material, or the surface of the fiber reinforcing yarn facing the nonwoven fabric sheet disposed on the outermost surface of the reinforcing fiber base material. Further, when the reinforcing fiber base material is laminated and pressed and heated so as to face the adjacent reinforcing fiber base material with the resin material for preform fixed to at least one of the surface of the stitch yarn exposed on the outermost surface of the reinforcing 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 reinforcing fiber base material, or the surface of the fiber reinforcing yarn facing the nonwoven fabric sheet disposed on the outermost surface of the reinforcing fiber base material, the resin material for preform adheres to the adjacent reinforcing fiber base material and can exhibit the effect of maintaining the shape of the deformed reinforcing fiber base material.

[0067] [Preferred embodiment regarding the form of the resin material for preform fixed] In the reinforcing fiber base material of the present invention, it is preferable that the surface of the resin material for preform fixed is a smooth surface.

[0068] FIG. 5 shows an enlarged plan view of the reinforcing fiber base material 8 in which the surface of the resin material 9 for preform fixed is a smooth surface.

[0069] The smooth surface refers to a state in which the surface has no sharp portions or fine irregularities and is composed of a rounded and smooth curved surface.

[0070] With such a configuration, even when the reinforcing fiber base materials laminated during shaping rub against each other, peeling of the resin material for preform from the reinforcing fiber base material, and displacement or cutting of the nonwoven fabric sheet, reinforcing fiber yarns, and stitch yarns can be suppressed. This is because it is difficult for the nonwoven fabric sheet and the reinforcing fiber yarns to catch on the surface of the resin material for preform. Further, since the friction coefficient of the surface of the reinforcing 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.

[0071] As a method for making the surface of the resin material for the preform smooth, for example, a method can be exemplified 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 strand and then solidified. Further, when using a granular resin material for the preform, a method can be exemplified 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 strand, melted, and then cooled and solidified. Furthermore, a method can be exemplified in which a resin material for the preform whose surface is not a smooth surface (for example, FIG. 2) is heated to a temperature equal to or higher than the melting point Tmb (°C), melted, and then cooled and solidified.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] The coverage rate of the resin material for 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 base material from the central portion in the width direction of the reinforced fiber base material. Next, using a microscope, photograph the surface on which the nonwoven fabric sheet with the resin material for preform fixed to the reinforced fiber base material is placed 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 where the resin material for preform is fixed among the fibers constituting the nonwoven fabric sheet, and divide it by the length Lv of the fibers constituting the nonwoven fabric sheet to obtain the coverage rate of the resin material for preform. In the fibers constituting the nonwoven fabric sheet in the evaluation image, if there is a section where the resin material for preform is fixed to any part in the circumferential direction, that section is regarded as the portion where the resin material for preform is fixed.

[0076] The above measurement can be carried out, for example, using a Keyence digital microscope VHX-8000.

[0077] The resin material for preform according to the reinforced fiber base material of the present invention preferably has a basis weight of 3 gsm or more and 50 gsm or less.

[0078] 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 arranged on the surface of the reinforced fiber base material, and the laminated reinforced 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.

[0079] The resin material for preform according to the reinforced fiber base material of the present invention is preferably in a granular form. By making it in a granular form, even when the basis weight of the resin material for preform is the same, the bulk height (apparent thickness) of the resin material for preform increases, so that the resin material for preform is likely to adhere so as to straddle between a certain reinforced fiber base material and an adjacent reinforced fiber base material in the preform, and a preform with excellent morphological stability can be obtained.

[0080] When the resin material for the preform according to the reinforcing fiber base material of the present invention is granular, the average particle size is preferably 50 μm or more and 1000 μm or less.

[0081] By setting the average particle size to be equal to or greater than the lower limit of the preferred range, the resin material for the preform can easily adhere so as to span between a certain reinforcing fiber base material and an adjacent reinforcing fiber base material, and a preform with excellent morphological stability can be obtained. On the other hand, by setting it to be equal to or less than the upper limit, the disturbance and voids of the reinforcing fibers can be suppressed, and an FRP with excellent mechanical properties can be obtained.

[0082] [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 the preform is lower than the melting point Tmv (°C) of the nonwoven fabric sheet and the melting point Tms (°C) of the stitch yarn.

[0083] 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 on the surface, the resin material for the preform can be firmly fixed to the nonwoven fabric sheet while maintaining the form of the original 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 on the surface of the nonwoven fabric sheet, by setting the heating temperature to be Tmb (°C) or more and Tmv (°C) or less, the resin material for the preform can be fixed to the nonwoven fabric sheet while maintaining the form of the nonwoven fabric sheet.

[0084] 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 form of the original reinforcing fiber base material. A preform with high strength and 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.

[0085] [Preferred embodiment of the method for 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 pattern to fix the reinforcing fiber yarn. Compared with the chain stitch that weaves the stitch yarn in a straight line, on the surface of the reinforcing fiber base material, the stitches face in multiple directions, and the length of the stitch yarn arranged on the surface of the reinforcing fiber base material becomes longer, so the non-woven fabric sheet can be firmly fixed to the reinforcing fiber base material. Therefore, 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.

[0086] Also, by using a 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.

[0087] In the method for fixing the stitch yarn according to the reinforcing fiber base material of the present invention, it is preferable that the gauge length is larger than the stitch length. With such a configuration, even when the reinforcing fiber base material is greatly sheared, the orientation direction of the stitches on the surface of the reinforcing fiber base material is less likely to be in the shearing direction of the reinforcing fiber base material, so it is easy to shape into a complex shape with a small load.

[0088] 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.

[0089] [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 Formula 1. K = Fb÷h÷M ···(Formula 1)

[0090] 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 areal density of the reinforcing fibers of the reinforcing fiber base material used in the bias extension test.

[0091] Here, the bias extension test measures the displacement and load when a tensile load is applied to the in-plane direction in which the reinforced fiber base material is shear-deformable. Note that the in-plane direction in which the reinforced fiber base material is shear-deformable is, when the reinforced fiber sheet in the reinforced fiber base material is oriented in only one axis, the direction at an angle of 45° with the orientation direction of the reinforced fiber yarn. Also, when the reinforced fiber sheet in the reinforced fiber base material 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 reinforced fiber sheet becomes maximum. For example, in the case of a reinforced fiber base material composed of a reinforced fiber sheet in which the reinforced fiber yarns are oriented in two directions of 0° (180°) and 90° (270°) respectively, the in-plane directions in which the reinforced fiber base material is shear-deformable are two directions of 45° and 135°.

[0092] The specific method of the bias extension test is as follows.

[0093] First, a rectangular test piece (length 230 mm × width 90 mm) is prepared so that the in-plane direction in which the reinforced fiber base material is shear-deformable becomes the longitudinal direction (Figure 3). Clamp both ends of this test piece, 25 mm each, and pull the test piece in the long axis direction with a distance between clamps of 180 mm and a test speed of 20 mm / min to measure the displacement and load. Note that the test temperature is room temperature (23°C).

[0094] In the bias extension test, as shown in Figure 4, 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 clamps, and the test speed changes. Therefore, in the present invention, the bias extension test is performed with the test piece and test speed of the above dimensions.

[0095] In the case where there are a plurality of in-plane directions in which the reinforced fiber base material is shear-deformable, the initial shear rigidity is calculated in each direction, and the largest value is taken as the initial shear rigidity of the reinforced fiber base material. For example, taking a reinforced fiber base material in which the reinforced fiber yarns are oriented in a biaxial direction of +45° and -45°, and the stitching direction (the weaving direction of the reinforced fiber base material) is the 0° direction as an example, the initial shear rigidity K 0 when the reinforced fiber base material is shear-deformed in the 0° direction, and the initial shear rigidity K 90 when the reinforced fiber base material is shear-deformed in the 90° direction are respectively obtained. At this time, due to the deformation resistance of the stitch yarn being added, K 0 >K 90 becomes true, so K 0 is adopted as the initial shear rigidity.

[0096] The initial shear rigidity can be controlled by the orientation direction of the reinforced fiber yarns in the reinforced fiber sheet when the reinforced fiber base material is used, the stitching pattern of the stitch yarns, and the tension during fixing. Also, the initial shear rigidity can be controlled by adjusting the type and basis weight of the reinforced fiber yarns, non-woven fabric sheet, preform resin material, and stitch yarns that make up the reinforced fiber base material. However, since it is caused by these deformation resistances and frictions, it is difficult to be lower than 1.5×10 -5 N / mm / gsm.

[0097] Also, it is important that the initial shear rigidity is 2.1×10 -4 N / mm / gsm or less. When an excess of the reinforced fiber base material occurs in the process of shaping the product shape, after the excess is diffused to some extent around by the shear deformation of the reinforced fiber base material, the remaining excess can be suppressed from generating large wrinkles by pressing it out of the plane. When the peak load of the bending test described later is appropriately set, by setting the initial shear rigidity to 2.1×10 -4 N / mm / gsm or less, the shear deformation of the reinforced fiber base material becomes easy, the excess of the reinforced fiber base material is easily diffused around, and the generation of large wrinkles can be suppressed.

[0098] The lower the initial shear rigidity value, the easier it is for the reinforcing fiber base material to undergo shear deformation, which is preferable in terms of formability. On the other hand, conventional reinforcing fiber base materials with a low initial shear rigidity value often have poor morphological stability. Therefore, as described later, it is important to combine with the resin material for the preform in an appropriate configuration in order to achieve both formability and morphological stability.

[0099] [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 2. P = Ff ÷ M 3 ···(Equation 2)

[0100] 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.

[0101] 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 8.1×10 -9 N / gsm 3 or less. When an excess of the reinforcing fiber base material occurs in the process of shaping it into the product shape, the excess can be diffused to the surroundings by shear-deforming the reinforcing fiber base material without buckling it in place, thereby suppressing the generation of wrinkles. By setting the peak load to 2.7×10 -9 N / gsm 3 or more, the reinforcing fiber base material becomes stiff, 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 8.1×10 -9 N / gsm 3 or less, even in a process where the load that can be applied to the reinforcing fiber base material is small or when the load is partially small, the remaining excess can be easily crushed out of the plane, and the generation of large wrinkles can be suppressed.

[0102] The loading jig used in the three-point bending test shall be the one described in JIS K 7074 (1988). 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).

[0103] The procedure for the three-point bending test is as follows. First, cut out rectangular test pieces (length 100 mm × width 50 mm) from the reinforced fiber base material to prepare the test pieces. At this time, with the stitching direction (the weaving direction of the reinforced fiber base material) as 0°, prepare each test piece so that the 0°, 45°, 90°, and 135° directions are the longitudinal directions of the test pieces. For each of the prepared test pieces, conduct a three-point bending test under the conditions of bending so that one surface contacts the upper jig support and the conditions of bending so that the other surface contacts the upper jig support. Place one test piece at the position where the upper jig support contacts the center of the longitudinal direction of the test piece, load the test piece at a test speed of 2 mm / min, and measure the maximum load Ff (N) generated in the three-point bending test. Conduct this measurement 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 minimum value or more and the maximum value or less of the peak load P of the bending test obtained from the test results of these 8 cases are the range of the peak load of the bending test.

[0104] Note that in the three-point bending test, it is necessary to pay attention that the measurement results will change when the dimensions of the test piece, the distance between the lower jig supports, or the test speed change. Therefore, in the present invention, the three-point bending test shall be conducted with the test piece of the above dimensions and the test speed.

Example

[0105] Hereinafter, the present invention will be further described using 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.

[0106] <Reinforced fiber yarn> PAN-based carbon fiber with 24,000 filaments, tensile strength: 6.0 GPa, and tensile modulus: 294 GPa was used.

[0107] <Stitch thread> An 18-filament, 33 dtex polyester thread was used as stitch thread A. The melting point was 260 °C and the breaking strain was 12%.

[0108] Two 4-filament, 23 dtex copolymer polyamide threads were plied together and used as stitch thread B. The melting point Tms was 140 °C and the breaking strain was 51%.

[0109] <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.

[0110] <Nonwoven fabric sheet> A resin prepared and polymerized so that polyamide 6 was 20 mol% and polyamide 12 was 80 mol% was made into a nonwoven fabric by a melt blowing apparatus 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. A resin prepared and polymerized so that polyamide 6 was 20 mol% and polyamide 12 was 80 mol% was made into a nonwoven fabric by a melt blowing apparatus to obtain a nonwoven fabric sheet B with a width of 1 m. The melting point Tmv was 150 °C, the basis weight was 30 gsm, and the fiber diameter was 40 μm.

[0111] (Example 1) A 1 m-wide reinforced fiber substrate [1] was produced by the following procedure.

[0112] (1) Nonwoven fabric placement step 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 the longitudinal direction 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) also during the subsequent lamination of the reinforced fiber sheet and the nonwoven fabric sheet, and continuously conveyed to the integration step described later.

[0113] (2) Arrangement Process of Reinforcing Fiber Yarns (First Direction) On the non-woven fabric sheet A, 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 in the -45° reinforcing fiber sheet was performed by a carriage device. The carriage device in this process reciprocates in the -45° direction, and when it moves forward (or backward) during that movement, it is a device that arranges the reinforcing fiber yarns on the belt conveyor. It was controlled so that the reinforcing fiber yarns did not overlap with each other 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.

[0114] (3) Arrangement Process of Reinforcing Fiber Yarns (Second Direction) A second non-woven fabric sheet A was placed on the -45° sheet, and on it, in the same manner as the -45° sheet formation, the reinforcing fiber yarns were arranged in parallel at +45° with respect to the longitudinal direction and at a density of 240 gsm to form a +45° reinforcing fiber sheet. Thereby, a laminate of (non-woven fabric sheet A / -45° reinforcing fiber sheet / non-woven fabric sheet A / +45° reinforcing fiber sheet) was produced.

[0115] (4) Integration Process Subsequently, the laminate on the belt conveyor formed as described above was stitched together with stitch yarn A to be integrated. 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 tricot knitting, with a stitch length of 3 mm and a gauge length of 5 mm. The non-woven fabric sheet A had excellent needle penetration, and the fibers of the non-woven fabric did not get entangled with the needle.

[0116] (5) Spraying Process of Resin Material for Preform Next, on the surface where the non-woven fabric sheet of the reinforcing fiber base material is disposed, the resin material A for preform was dropped while being measured so that the mass per unit area was 10 gsm using an embossing roll and a doctor blade, and uniformly dispersed. Subsequently, by passing it under an infrared heater set so that the surface temperature of the reinforcing fiber base material becomes 100°C at a speed of 0.3 m / min, the resin material A for preform was fixed to the surface of the reinforcing fiber base material, wound around a roll, and the reinforcing fiber base material [1] was obtained. When the surface of the reinforcing fiber base material [1] was observed, the surface of the resin material for preform was smooth and rounded, and was a smooth surface.

[0117] (Example 2) A 1 m-wide reinforcing fiber base material [2] was produced in the same procedure as in Example 1 except that the first direction was 0° and the second direction was 90°.

[0118] (Example 3) A 1 m-wide reinforcing fiber base material [3] was created in the same procedure as in Example 1 except that non-woven fabric sheet B was used instead of non-woven fabric sheet A.

[0119] (Example 4) A 1 m-wide reinforcing fiber base material [4] was created in the same procedure as in Example 2 except that non-woven fabric sheet B was used instead of non-woven fabric sheet A.

[0120] (Comparative Example 1) A 1 m-wide comparative reinforcing fiber base material [1c] was produced by the following procedure.

[0121] (1) Non-woven fabric placement step The non-woven fabric sheet A was continuously placed on the belt conveyor so that the longitudinal direction of the non-woven fabric sheet A was parallel to the longitudinal direction 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) even during the subsequent lamination of the reinforcing fiber sheet and the non-woven fabric sheet, and continuously conveyed to the integration step described later.

[0122] (2) Arrangement step of reinforcing fiber yarns (first direction) On the non-woven fabric sheet A, the reinforced fiber yarns that were horizontally opened and loosened without mixing in the loosening twist were arranged in parallel at -45° with respect to the longitudinal direction (the direction in which the belt conveyor conveys, 0° direction) and arranged so as to be 240 gsm to form a -45° reinforced fiber sheet. The arrangement of the reinforced fiber yarns of the -45° reinforced fiber sheet was performed by a carriage device. The carriage device in this step reciprocates in the -45° direction, and when moving forward (or backward) therein, it is a device for arranging the reinforced fiber yarns on the belt conveyor. It was controlled so that the reinforced 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.

[0123] (3) Arrangement step of reinforced fiber yarns (second direction) The second non-woven fabric sheet A was placed on the -45° sheet, and on it, the -45° sheet In the same manner as the formation, the reinforced fiber yarns were arranged in parallel at +45° with respect to the longitudinal direction and arranged so as to be 240 gsm to form a +45° reinforced fiber sheet. Thereby, a laminate of (non-woven fabric sheet A / -45° reinforced fiber sheet / non-woven fabric sheet A / +45° reinforced fiber sheet) was produced.

[0124] (4) Integration step Subsequently, the laminate on the belt conveyor formed as described above was stitched with stitch yarn A to be integrated, and a comparative reinforced fiber base material [1c] was obtained. 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 penetration, and the fibers of the non-woven fabric did not get caught on the needle.

[0125] (Comparative Example 2) With the first direction being 0° and the second direction being 90°, a 1 m-wide reinforced 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.

[0126] (Comparative Example 3) On the surface where the non-woven fabric of the comparative reinforced fiber base material [1c] is not disposed, the resin material A for preform was dropped while being measured to have a mass per unit area of 10 gsm using an embossing roll and a doctor blade, and uniformly dispersed. Subsequently, the resin material A for preform was fixed onto the comparative reinforced fiber base material [1c] by passing it under an infrared heater set so that the surface temperature of the reinforced fiber base material became 100°C at a speed of 0.3 m / min, and the comparative reinforced fiber base material [3c] with the resin material A for preform fixed to the reinforced fiber was produced.

[0127] (Comparative Example 4) A comparative reinforced fiber base material [4c] was produced in the same procedure as Comparative Example 3 except that the comparative reinforced fiber base material [1c] was changed to the comparative reinforced fiber base material [2c].

[0128] ≪Evaluation Method≫ As described above, morphological stability is required for the lamination process and the conveying process, and formability is required for the preform process. The process passability in each process can be clarified by evaluating (i) lamination workability, (ii) complex shape formability (wrinkles), (iii) complex shape formability (bulges), (iv) complex shape formability (stitch breakage), and (v) preform conveyability. 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.

[0129] The characteristic evaluation method of the reinforced fiber base material and the evaluation methods of (i) to (v) above are shown below.

[0130] (Initial shear rigidity of the reinforced fiber base material) From each reinforced fiber base material, three test pieces were cut out for all in-plane directions in which the reinforced fiber base material could be shear-deformed so that the end of the non-woven fabric sheet was not included, and a bias extension test was conducted to obtain the average value of the initial shear rigidity K.

[0131] (Bending characteristics) Six specimens were cut out from each reinforcing fiber base material so that the ends of the nonwoven fabric sheet were not included, and six specimens were cut out for each of the longitudinal directions of 0°, 45°, 90°, and 135°. The three-point bending test was performed three times under the condition of bending so that one surface and the other surface contacted the upper jig fulcrum respectively, and the average value of the peak load P of eight bending tests was obtained respectively, and the minimum value and the maximum value among them were obtained.

[0132] (Laminating workability) One specimen with a length of 1000 mm and a width of 300 mm was cut out from each reinforcing fiber base material so that the ends of the nonwoven fabric sheet were not included, and the longitudinal directions were 0° and 45°. Subsequently, two specimens were laminated so that the whole of the two specimens overlapped to form a laminate. At this time, when the longitudinal direction of the laminate was 0°, the reinforcing fiber yarns of each reinforcing fiber sheet were laminated so that the orientation directions were -45°, 45°, 0°, and 90° from the lower surface. That is, the lamination structure of the laminate is [-45° / 45° / 0° / 90°].

[0133] In this series of operations, the lamination workability was evaluated in five stages shown in A to E below, and C or above was regarded as 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.

[0134] 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. When there is no change in the projected area, it means that there is no change of 0.5% or more. Also, for the stitch length and the 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 (less than 50 repeating units is rounded down) 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.

[0135] (Complex shape formability) The formability of the reinforcing fiber base material into a complex shape was evaluated using an aluminum forming jig with a length of 1100 mm, a width of 90 mm, and a height (depth direction in the plane of FIG. 6) of 70 mm shown in FIG. 6. The forming jig is installed on a metal table (length 2000 mm, width 1000 mm) not shown, and the metal table has an exhaust port that can be opened and closed at a position where it does not interfere with the forming jig or the laminate. Subsequently, the laminate whose lamination workability was evaluated was arranged in the shape of the forming jig in the positional relationship shown in FIG. 7. At this time, a part of the laminate extended from the upper surface of the forming jig to the surroundings and hung down to the lower surface side due to its own weight. Further, as shown in FIG. 8, the forming 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 forming jig 12 by utilizing the force with which the thermoplastic film 90 follows the forming jig 12. Here, a regulator with a set pressure of 0.05 MPa was installed between the vacuum pump and the exhaust port to simulate the case where the load becomes locally small. When the exhaust was completed, the vacuum pressure was -0.05 MPa in gauge pressure.

[0136] Regarding the wrinkles in this series of shaping, the number of wrinkles generated and the length and height of the maximum wrinkle were recorded. The dimensions of the wrinkles were measured using a non-contact three-dimensional measuring machine ATOS manufactured by Zeiss while applying a vacuum pressure, and values less than 1 mm were rounded up. Furthermore, regarding the ease of following the substrate, when the substrate followed the concave part that is the boundary between the shaping jig and the metallic table, it was classified as A, when a slight bulge occurred, it was classified as B, and when a bulge of medium level or more that affected injection molding occurred, it was classified as C. B or higher was considered a pass. Also, the number of broken stitch threads on both the thermoplastic film side and the shaping jig side of the preform was recorded.

[0137] (Preform transportability) Regarding the laminated body after shaping was completed, while continuing evacuation, it was put into an oven heated to 110 °C together with the metallic table, taken out of the oven 10 minutes after the surface temperature of the aluminum shaping jig reached 100 °C, and cooled at room temperature. By this operation, the laminated body was fixed and integrated with the resin material for the preform to obtain a preform. Then, the thermoplastic film was peeled off, the preform was removed from the shaping jig, and it was carried to an injection molding apparatus 10 m ahead while holding both ends in the longitudinal direction by hand. In this series of transport operations, the lamination workability was evaluated in five stages shown in A to E below, and C or higher was considered a pass. A: After transport, the layers of all the reinforcing fiber sheets constituting the laminated body are firmly adhered over the entire surface, and no partial peeling is observed. B: After transport, the layers of all the reinforcing fiber sheets constituting the laminated body are firmly adhered over the entire surface, but partial peeling is observed in one layer. C: After transport, the layers of all the reinforcing fiber sheets constituting the laminated body are firmly adhered over the entire surface, but partial peeling is observed in two or more layers. D: A large peeling occurred in any of the layers of all the reinforcing fiber sheets constituting the laminated body after transport. E: The reinforcing fiber base material became scattered and could not be handled as a preform.

[0138] As a result of the above evaluations, the reinforcing fiber base materials [1] to [6] shown in the examples exhibited excellent formability and morphological stability, and thus had excellent laminating workability, did not cause wrinkles or bulges even when formed into complex shapes, and also had excellent preform transportability. The manufactured preforms with complex shapes were of high quality and high precision without cuts on the final product surface. Furthermore, among these, 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 during forming into complex shapes.

[0139] In addition, the reinforcing fiber base material shown in Reference Example [1'] had excellent laminating workability and did not cause wrinkles or bulges even when formed into complex shapes, exhibiting excellent formability. However, the proportion of the surface of the nonwoven fabric sheet coated with the resin material for the preform was smaller than that of the other examples, and the reinforcing fiber base material was partially peeled off during preform transport, causing disturbance in the reinforcing fiber yarns.

[0140] On the other hand, although the comparative reinforcing fiber base materials [1c] and [2c] shown in Comparative Examples 1 and 2 did not cause wrinkles or bulges when formed into complex shapes because they did not have the resin material for the preform, they were inferior in laminating workability and caused disturbance in the reinforcing fiber yarns. Furthermore, they could not maintain the three-dimensional shape of the preform. In addition, although the comparative reinforcing fiber base materials [3c] and [4c] shown in Comparative Examples 3 and 4 had their forms maintained by the resin material for the preform and were excellent in laminating workability, they had large wrinkles and bulges when formed into complex shapes, resulting in inferior formability.

[0141]

Table 1

[0142]

Table 2

Industrial Applicability

[0143] The reinforced fiber base material of the present invention can also be suitably used for large members for aircraft, automobiles, ships, etc., and members for general industrial applications such as windmill blades.

Explanation of reference numerals

[0144] Y Reinforced fiber yarn 1 Reinforced fiber sheet (0 degrees) 2 Reinforced fiber sheet (+45 degrees) 3 Reinforced fiber sheet (90 degrees) 4 Reinforced fiber sheet (-45 degrees) 5A Nonwoven fabric sheet disposed on the surface of the reinforced fiber base material 5B Nonwoven fabric sheet disposed between the layers of the reinforced fiber base material 51 Fibers constituting the nonwoven fabric sheet 6 Stitch thread 7 Needle 8 Reinforced fiber base material 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 in which a non-woven fabric sheet is fixed with a stitch thread on one or both surfaces of a reinforced fiber sheet formed by aligning reinforced fiber yarns in parallel, wherein (a) the non-woven fabric sheet is disposed on at least one outermost surface of the reinforced fiber base material, and (b) at least one of the surface of the stitch thread exposed on the outermost surface of the reinforced fiber base material where the non-woven fabric sheet is disposed, the entire surface of the fibers constituting the non-woven fabric sheet disposed on the outermost surface of the reinforced fiber base material, or the surface of the fiber reinforced yarn facing the non-woven fabric sheet disposed on the outermost surface of the reinforced fiber base material has a preform resin material fixed thereto. (c) The initial shear rigidity is 1.5×10 －５ N / mm / gsm or more and 2.1×10 －４ N / mm / gsm or less, and (d) The peak load of the bending test is 2.7×10 －９ N / g·sm³ or more and 8.1×10 －９ N / g·sm ３ or less, characterized by a reinforced fiber substrate.

2. The reinforced fiber base material according to claim 1, wherein the basis weight of the non-woven fabric sheet is 10 gsm or more and 50 gsm or less.

3. The reinforced fiber base material according to claim 1, wherein the average fiber diameter of the non-woven fabric sheet is 1 μm or more and 100 μm or less.

4. The reinforced fiber base material according to claim 1, wherein the surface of the preform resin material fixed to the non-woven fabric sheet is a smooth surface.

5. The reinforced fiber base material according to claim 1, wherein 50% or more and 100% or less of the surface of the non-woven fabric sheet is coated with a preform resin material.

6. The reinforced fiber base material according to claim 1, wherein the basis weight of the preform resin material is 3 gsm or more and 50 gsm or less.

7. The reinforced fiber base material according to claim 1, wherein the preform resin material is granular.

8. The reinforced fiber base material according to claim 7, wherein the average particle diameter of the preform resin material is 50 μm or more and 1000 μm or less.

9. The reinforced fiber base material according to claim 1, wherein the melting point Tmb (°C) of the preform resin material is lower than the melting point Tmv (°C) of the non-woven fabric sheet and the melting point Tms (°C) of the stitch thread.

10. The reinforced fiber base material according to claim 1, wherein the fixing method of the stitch thread is tricot knitting.

11. Among a plurality of laminated reinforced fiber sheets with the nonwoven fabric sheet fixed thereto, 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.

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