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 finished product surface even in a complicated shape.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) the nonwoven fabric sheet is disposed on the outermost surface of at least one of the reinforcing fiber substrate, (b) a resin material for a preform is adhered to the surface of the entire fibers constituting the nonwoven fabric sheet disposed on the outermost surface, and (c) the initial shear stiffness is 1.5×10-5 N / mm / gsm or more and 1.5×10-4 N / mm / gsm or less.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 shape 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 aviation, aerospace, automotive applications, etc. because of their characteristics of being lightweight and 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 reinforced fiber 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 formed by laminating unidirectional layers (reinforced fiber sheets) of reinforcing fibers having a predetermined basis weight in a plurality of directions such as two axes or three axes, and stitched and integrated through the thickness direction of the laminate with a stitch yarn has been proposed. 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 lower the viscosity of the matrix resin, the mechanical properties may not be fully exhibited compared to FRP formed from the high-viscosity matrix resin used in 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, the mechanical properties in the compression after impact (CAI) test, which is generally used to characterize the impact resistance of the structure, can be improved.

[0005] In the injection molding method for products having a three-dimensional shape, a preform obtained by previously shaping and integrally fixing a laminate of a reinforcing fiber base material into the product shape may be used. The manufacturing process of the preform can be divided into a lamination process of laminating the reinforcing fiber base materials cut to the 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 the 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 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 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 cuts 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 preform fixed to its surface. After fixing the resin material for preform to the surface of the reinforced fiber base material, by varying the relative positions of a plurality of reinforcing fiber yarns constituting the reinforced fiber base material, a reinforced fiber base material is proposed in which the resin material for preform fixed across two or more reinforcing fiber yarns is peeled off from a part of the two or more reinforcing 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 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 molding defects and a decrease in appearance quality due to the wrinkles. On the other hand, when the resin material for 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 transportation 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 reinforced fibers, or cases where the appearance quality is impaired because the cuts can be visually recognized from the product surface.

[0013] Also, in the reinforced fiber base material from which the resin material for the fixed preform as described in Patent Document 3 is peeled off, 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 reinforced 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 in the same document, a resin material for the preform different from the composite nonwoven fabric sheet is additionally used in the preform process.

[0015] 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 with no cuts on the final product surface even with a complex shape.

[0016] Therefore, the problem of the present invention is to provide a reinforced fiber base material that is excellent in formability and form stability, can stably manufacture a high-quality and high-precision preform with no cuts on the final product surface even with a complex shape, by focusing on the above problems.

Means for Solving the Problem

[0017] As a result of investigations to solve the above problems, the present inventors have found that morphological stability is required for the lamination process and the conveyance process, and formability is required for the preform process. Therefore, when examining the influence of the fixed form of the resin material for preform on the process passability of each process and the influence of the formability of the reinforced fiber base material, it has been found that for the first time by using the reinforced fiber base material of the present invention shown below, the form is stable in the lamination process and the conveyance process, and excellent formability is exhibited in the preform process. 〔1〕A reinforced fiber base material obtained by laminating one or more non-woven fabric-attached reinforced fiber sheets, in which non-woven fabric sheets are arranged on one or both sides of a reinforced fiber sheet formed by aligning reinforced fiber yarns in parallel and fixing them with stitch yarns, (a) The non-woven fabric sheet is arranged on at least one outermost surface of the reinforced fiber base material, (b) The resin material for preform is fixed to the entire surface of the fibers constituting the non-woven fabric sheet arranged on the outermost surface, (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. The reinforced fiber base material is characterized by this. 〔2〕The reinforced fiber base material according to 〔1〕, wherein the basis weight of the non-woven fabric sheet is 1 gsm or more and 50 gsm or less. 〔3〕The reinforced fiber base material according to 〔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 〔1〕, wherein the surface of the resin material for preform fixed to the non-woven fabric sheet is a smooth surface. 〔5〕The reinforced fiber base material according to 〔1〕, wherein 50% or more and 100% or less of the surface of the non-woven fabric sheet is covered with the resin material for preform. 〔6〕The reinforced fiber base material according to 〔1〕, wherein the basis weight of the resin material for preform is 3 gsm or more and 50 gsm or less. 〔7〕The reinforced fiber base material according to 〔1〕, wherein the resin material for preform is granular. 〔8〕The reinforcing fiber base material according to 〔7〕, wherein the average particle size 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 nonwoven fabric sheet and the melting point Tms (°C) of the stitch thread. 〔10〕The reinforcing fiber base material according to 〔1〕, wherein the method of fixing the stitch thread is tricot knitting. 〔11〕Among the reinforcing fiber sheets with nonwoven fabric laminated in multiple layers, 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 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

[0018] According to the present invention, it is possible 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 surface of the final product even with a complex shape.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0020] The reinforced fiber base material of the present invention is a reinforced fiber base material in which one or more non-woven fabric sheets are laminated on one or both surfaces of a reinforced fiber sheet formed by aligning reinforced fiber yarns in parallel, and fixed with stitch yarns. (a) The non-woven fabric sheet is disposed on at least one outermost surface of the reinforced fiber base material. (b) A resin material for preform is fixed to the entire surface of the fibers constituting the non-woven fabric sheet disposed on the outermost surface. (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.

[0021] Hereinafter, the present invention will be described in detail with reference to the drawings together with embodiments.

[0022] [Outline of Reinforced Fiber Base Material] FIG. 1 shows an embodiment of the reinforced fiber base material of the present invention. The reinforced fiber base material 8 of the present invention includes a reinforced fiber sheet (1, 2, 3, 4) formed by aligning reinforced fiber yarns Y in parallel, non-woven fabric sheets (5A, 5B) disposed on one or both surfaces of the reinforced fiber sheet, stitch yarns 6, and a resin material for preform as components. The reinforced fiber sheet (1, 2, 3, 4) and the non-woven fabric sheets (5A, 5B) are stitched and integrated with stitch yarns 6 in the stitching direction (weaving direction) indicated by the arrows by an up-and-down moving needle 7 to form the reinforced fiber base material 8.

[0023] Since the reinforcing fiber yarns constituting the reinforcing fiber base material are hardly bent, the molded product after matrix resin injection has excellent mechanical properties, 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 (particularly primary structure) members of transportation equipment (particularly aircraft).

[0024] [Reinforcing fiber sheet] The reinforcing fiber sheet used for the reinforcing fiber base material of the present invention is composed of reinforcing fiber yarns aligned in parallel. 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 the stitch yarn for fixing the reinforcing fiber base material.

[0025] Since the reinforcing fiber sheet according to the present invention can obtain excellent mechanical properties, it is preferably in a form composed of continuous fiber reinforcing fiber yarns.

[0026] Examples of the reinforcing fiber yarns include carbon fibers, glass fibers, aramid fibers, alumina fibers, silicon carbide fibers, boron fibers, and silicon carbide fibers. Among them, from the viewpoints of mechanical strength and light weight, it is preferable to use carbon fibers having a high specific elastic modulus.

[0027] The reinforcing fiber yarn is a bundle of 1000 to 60000 single reinforcing fibers (also called single filaments). It is preferable to use 3000 to 50000 single filaments for one reinforcing fiber yarn, and more preferably 6000 to 24000 single filaments.

[0028] When carbon fiber is selected 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. 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.

[0029] Examples of commercially available carbon fibers include "Torayca (registered trademark)" T1100GC-12K, "Torayca (registered trademark)" T800SC-12K, "Torayca (registered trademark)" T700SC-12K (manufactured by Toray Industries, Inc., etc.).

[0030] Examples of the form of making a reinforcing fiber sheet using the reinforcing fiber yarn include a unidirectional form in which the reinforcing fiber yarns are aligned in one direction, or a non-crimp form in which the reinforcing fiber yarns aligned in one direction are laminated on one axis or multiple axes.

[0031] [Nonwoven fabric sheet] In the present invention, the nonwoven fabric sheet refers to a material in which the fibers are oriented in one direction or randomly, and the fibers are bonded to each other by alternating current, and / or heat fusion, and / or adhesion.

[0032] Figure 2 shows an embodiment of the nonwoven fabric sheet of the present invention.

[0033] In the reinforcing fiber base material of the present invention, the nonwoven fabric sheets (5A, 5B) are arranged on one or both sides of the reinforcing fiber sheet, and it is important that the nonwoven fabric sheet is arranged on at least one outermost surface of the reinforcing fiber base material. Further, the resin material 9 for preform must be fixed to the entire surface of the fibers constituting the nonwoven fabric sheet 5A arranged on at least one outermost surface of the reinforcing fiber base material.

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

[0035] In the interior of the reinforcing fiber base material, that is, in the nonwoven fabric sheet 5B arranged 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.

[0036] As the fibers 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 to the surface and the mechanical properties in the compression after impact (CAI) test can be improved, the material is not particularly limited.

[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 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.

[0038] In addition, from the viewpoint that a layer with high toughness can be formed between the layers of the FRP to enhance the mechanical properties (especially CAI), the synthetic fiber used as the stitch thread 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 the 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 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. 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 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.

[0041] By making the basis weight larger than the lower limit, a sufficient amount of the resin material for the preform can be fixed to the nonwoven fabric sheet for the solidification and integration of the reinforcing fiber base materials. On the other hand, by making it below the upper limit, the burial and impregnation of the resin material for the 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.

[0042] The nonwoven fabric 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.

[0043] 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 to the nonwoven fabric surface. On the other hand, by setting it to be equal to or less than the upper limit, the fiber diameter becomes thinner. Therefore, even when the basis weight of the nonwoven fabric sheet is small, the surface area increases, the amount of the resin material for the preform fixed can be increased, and a sufficient amount of the resin material for the preform can be fixed to the nonwoven fabric sheet to achieve solidification and integration of the reinforcing fiber base materials with each other.

[0044] [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 disposing a nonwoven fabric sheet on one or both sides of the reinforcing fiber sheet.

[0045] At this time, when a plurality of reinforcing fiber sheets with nonwoven fabric 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 contrary, when a plurality of reinforcing fiber sheets with nonwoven fabric in which the nonwoven fabric sheets are 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.

[0046] Since the arrangement process of the nonwoven fabric sheet can be halved and the manufacturing apparatus and process can be simplified, it is preferable that the nonwoven fabric sheet is disposed on one side of the reinforcing fiber sheet.

[0047] 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 plurality of laminated reinforcing fiber sheets with nonwoven fabric, and it is preferable that the first direction and the second direction are orthogonal to each other.

[0048] 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 in-plane directions capable of shear deformation. Therefore, even when shaping a laminate reinforced in a plurality of directions by the reinforcing fiber yarns into a product having a complex shape, there is room for shear deformation in the reinforcing fiber base material, so it is difficult for the reinforcing fiber yarns to cause tension and it is easy to shape.

[0049] From the viewpoint of simplifying the lamination operation, among the plurality of reinforced fiber sheets with nonwoven fabric laminated, it is preferable that the alignment direction of the reinforced fiber yarns is three or more directions. In particular, for example, like [(0° / 90°) / (+45° / -45°)], while making the alignment direction of the reinforced fiber yarns orthogonal, increasing the orientation direction of the reinforced fiber yarns enables a configuration that reinforces in multiple directions and is also rich in formability. Since such a reinforced fiber base material has a plurality of reinforcement directions in one sheet, there is an advantage that the lamination operation is simplified and FRP can be obtained at low cost.

[0050] From the viewpoint of further improving the formability, it is more preferable that the alignment direction of the reinforced fiber yarns of the plurality of layers of reinforced fiber sheets constituting the reinforced fiber sheet with nonwoven fabric is only in the first / second directions. Such a reinforced fiber base material with a biaxial orientation direction of the reinforced fiber yarns is more likely to shear-deform and has excellent formability compared to a triaxial or quadraxial base material, and is likely to reduce the initial shear rigidity.

[0051] [Stitch yarn] As the stitch yarn for the reinforced fiber base material of the present invention, for example, synthetic fibers can be used, but it is only necessary that it can be used to fix the reinforced fiber sheet and the nonwoven fabric sheet, and the material is not particularly limited.

[0052] When using synthetic fibers as the stitch yarn, the material can be the same as the synthetic fibers used for the nonwoven fabric sheet.

[0053] Also, from the viewpoint of improving the shape stability of the reinforced 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 reinforced 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 plastically deformed and is difficult to break, and the form of the reinforced fiber base material can be maintained even when the reinforced fiber base material is formed into a complex shape.

[0054] Also, similar to the nonwoven fabric sheet, from the viewpoint of suppressing the deterioration of the 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 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 preferable 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.

[0055] 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, 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, 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.

[0056] 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.

[0057] 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 to obtain the fineness (unit: dtex).

[0058] [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 but have the property of melting or softening by heat.

[0059] Examples of the thermoplastic resin used as the resin material for the preform include 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. 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 adhering the layers, and the productivity is improved. Note that the main component refers to the component with the largest proportion among the components constituting the resin material.

[0060] As the form of the resin material for the preform, a resin material for the preform in the form of fibrous, powdery, etc. can be used. The fixing location is the entire surface of the fibers constituting the nonwoven fabric sheet, and it is not fixed to the surfaces of the reinforcing fiber yarns and the stitch yarns. As the fixing method, for example, a resin material for the preform in the form of fibrous, powdery, etc. is sprayed on the surface of the nonwoven fabric and then heated and softened to bond the fibers constituting the nonwoven fabric sheet and the resin material for the preform, and then cooled and solidified. Further, a method of spraying a liquid resin material for the preform on the surface of the nonwoven fabric sheet and then solidifying it can be exemplified. Furthermore, a method can be exemplified in which an adhesive different from the resin material for the preform is attached to the surface of the nonwoven fabric sheet, then the resin material for the preform is attached to the adhesive on the surface of the nonwoven fabric sheet, and then the adhesive is cured. However, it is not limited to these methods.

[0061] [Preferred embodiment regarding the form of the resin material for the preform fixed to the nonwoven fabric sheet] In the reinforcing fiber base material of the present invention, it is preferable that the surface of the resin material for the preform fixed to the nonwoven fabric sheet is a smooth surface.

[0062] Fig. 5 shows an enlarged plan view of the nonwoven fabric sheet 5A (5B) in which the surface of the fixed resin material 9 for the preform is a smooth surface.

[0063] 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.

[0064] With such a configuration, even when the reinforcing fiber base materials laminated during shaping are rubbed against each other, peeling of the resin material for the preform from the reinforcing fiber base material, or 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 the preform. In addition, since the friction coefficient on 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 with a thickness exceeding 2 mm.

[0065] As a method for making the surface of the resin material for the preform smooth, a method can be exemplified in which a liquid resin material for the preform is sprayed on the surface of a nonwoven fabric sheet 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 nonwoven fabric surface, melted, and then cooled and solidified. Furthermore, a method can be exemplified in which a resin material for the preform (for example, FIG. 2) having a non-smooth surface is heated to a temperature equal to or higher than the melting point Tmb (°C), melted, and then cooled and solidified.

[0066] It is preferable that 50% or more and 100% or less of the surface of the nonwoven fabric sheet related to the reinforcing fiber base material of the present invention is covered with the resin material for the preform.

[0067] 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, when laminated and integrated, the reinforcing fiber base materials are firmly fixed to each other, and a preform with excellent morphological stability can be obtained.

[0068] For the same reason, it is preferable that the nonwoven fabric sheet related to the reinforcing fiber base material of the present invention is arranged 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.

[0069] 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 reinforcing fiber base material from the central part in the width direction of the reinforcing 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 reinforcing 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 part 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 part where the resin material for preform is fixed.

[0070] The above measurement can be carried out, for example, using a Keyence digital microscope VHX-8000.

[0071] 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.

[0072] 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 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.

[0073] The resin material for preform according to the reinforcing 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 span between a certain reinforcing fiber base material and an adjacent reinforcing fiber base material in the preform, and a preform with excellent morphological stability can be obtained.

[0074] 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.

[0075] 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.

[0076] [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.

[0077] 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 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 to the surface of the nonwoven fabric sheet, by setting the heating temperature to be Tmb (°C) or higher and Tmv (°C) or lower, the resin material for the preform can be fixed to the nonwoven fabric sheet while maintaining the form of the nonwoven fabric sheet.

[0078] 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 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.

[0079] [Preferred embodiment of the method for fixing the stitch yarn] The method for fixing the stitch yarn 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 yarns. 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, thereby also improving the form stability of the finally obtained preform.

[0080] 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.

[0081] 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 undergoes large shear deformation, 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 into a complex shape with a small load.

[0082] 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 morphological stability of the reinforcing fiber base material is improved.

[0083] [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 1. K = Fb÷h÷M ···(Equation 1)

[0084] 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 base material used in the bias extension test. Note that gsm is equal to g / m 2 is equal to.

[0085] 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 reinforcing 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 reinforcing fiber yarn. Also, when the reinforcing 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 reinforcing fiber sheet becomes maximum. For example, in the case of a reinforced fiber base material 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 reinforced fiber base material is shear-deformable are two directions of 45° and 135°.

[0086] The specific method of the bias extension test is as follows.

[0087] 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). The two ends of this test piece, 25 mm each, are clamped with chucks, and the test piece is pulled in the long axis direction with a distance between chucks of 180 mm and a test speed of 20 mm / min, and the displacement and load are measured. Note that the test temperature is room temperature (23°C).

[0088] 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 chucks, and the test speed changes. Therefore, in the present invention, the bias extension test is performed using the test piece and test speed of the above dimensions.

[0089] In addition, when there are multiple 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 Therefore, K 0 is adopted as the initial shear rigidity.

[0090] 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 yarn, and the tension during fixing. In addition, the initial shear rigidity can be controlled by adjusting the types and basis weights of the reinforced fiber yarns, non-woven fabric sheets, preform resin materials, and stitch yarns that make up the reinforced 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.

[0091] The smaller the value of the initial shear rigidity, the easier it is for the reinforced fiber base material to be shear-deformed, which is preferable in terms of formability. On the other hand, conventional reinforced 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.

[0092] In addition, the initial shear rigidity is 1.5×10 -4It is important that it be below -4 N / mm / gsm. Since the reinforcing fiber base material has a high tensile deformation resistance in the orientation direction of the reinforcing fiber yarns, it is mainly shaped into the product shape by shear deformation. At this time, if the reinforcing fiber base material cannot be sufficiently sheared, the reinforcing fiber base material may be locally compressed, resulting in defects such as wrinkles and meandering of the reinforcing fiber yarns. On the other hand, by setting the initial shear rigidity to 1.5×10

[0093] [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)

[0094] 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.

[0095] The load jig used in the three-point bending test is the load jig 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).

[0096] The procedure for the three-point bending test is as follows. First, rectangular test pieces (length 100 mm × width 50 mm) are cut out 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°, each test piece is prepared so that the 0°, 45°, 90°, and 135° directions are the longitudinal directions of the test pieces. For each of the prepared test pieces, a three-point bending test is performed under the conditions of bending such that one surface contacts the upper jig fulcrum and under the conditions of bending such that the other surface contacts the upper jig fulcrum. One test piece is placed at the position where the upper jig fulcrum 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 fulcrum. 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.

[0097] 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 fulcrums, and the test speed change. Therefore, in the present invention, the three-point bending test is performed using test pieces of the above dimensions and the test speed.

Example

[0098] 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.

[0099] <Reinforced fiber yarn> PAN-based carbon fiber, 24,000 filaments, tensile strength: 6.0 GPa, tensile elastic modulus: 294 GPa was used.

[0100] <Stitch yarn> An 18-filament, 33 dtex polyester yarn was used as stitch yarn A. The melting point was 260°C and the breaking strain was 12%.

[0101] Two 23dtex copolymer polyamide yarns with 4 filaments were combined and used as the stitch yarn B. The melting point Tms (°C) was 140°C, and the breaking strain was 51%.

[0102] <Resin material for preform> A granular resin material for preform, EP05311 manufactured by Hexion, was used as the resin material A for preform. The melting point Tmb (°C) was 70°C, and the average particle size was 70 μm.

[0103] <Non-woven fabric sheet> A resin prepared by adjusting and polymerizing polyamide 6 to 20 mol% and polyamide 12 to 80 mol% was made into a non-woven fabric by a melt blowing device to obtain a non-woven fabric sheet A with a width of 1 m. The melting point Tmv (°C) was 150°C, the basis weight was 10 gsm, and the fiber diameter was 40 μm.

[0104] After cutting the non-woven fabric sheet A into a size of 1 m width × 1 m length, Spray Adhesive 55 manufactured by 3M was sprayed onto the entire surface as an adhesive for fixing the resin material for preform, and 2.5 g / m² of the adhesive was attached. Next, the non-woven fabric sheet A with the adhesive attached and 30 g of the resin material A for preform were quickly sealed in a closed container. Subsequently, by shaking the closed container by hand, the resin material A for preform was fixed to the surface of the non-woven fabric sheet A through the adhesive to obtain a non-woven fabric sheet B. The fixed resin material A for preform was 20 g and was uniformly distributed on the surface of the non-woven fabric sheet. The surface of the resin material for preform fixed to the non-woven fabric sheet B had fine irregularities and was pointed, not a smooth surface. Also, 90% of the surface of the non-woven fabric sheet B was covered with the resin material A for preform.

[0105] Furthermore, the non-woven fabric sheet B was heated in an oven at 100°C for 3 minutes and then cooled to room temperature to obtain a non-woven fabric C. The surface of the resin material for preform fixed to the non-woven fabric sheet C was smooth and rounded, a smooth surface. Also, 90% of the surface of the non-woven fabric sheet C was covered with the resin material A for preform.

[0106] Subsequently, after cutting the nonwoven fabric sheet A into a size of 1 m width × 1 m length, Spray Adhesive 55 manufactured by 3M was sprayed over the entire surface as an adhesive for fixing the resin material for preform, and 0.5 g per minute of the adhesive was adhered. Next, the nonwoven fabric sheet A with the adhesive adhered and 2 g of the resin material A for preform were promptly sealed in a closed container. Subsequently, by shaking the closed container by hand, the resin material A for preform was fixed to the surface of the nonwoven fabric sheet A via the adhesive, obtaining the nonwoven fabric sheet D. The fixed resin material A for preform was 2 g and was distributed sporadically on the surface of the nonwoven fabric sheet. The surface of the resin material for preform fixed to the nonwoven fabric sheet D was rough and uneven, not a smooth surface. Also, 10% of the surface of the nonwoven fabric sheet D was covered with the resin material A for preform.

[0107] (Example 1) A 1 m-width reinforced fiber base material [1] was produced in the following procedure.

[0108] (1) Nonwoven fabric placement process A 1 m-length nonwoven fabric sheet B was placed on a belt conveyor such that the longitudinal direction of the nonwoven fabric sheet B was parallel to that of the belt conveyor. Care was taken to ensure that multiple nonwoven fabric sheets B did not overlap on 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 reinforced fiber sheet and the nonwoven fabric sheet, and was continuously conveyed to the integration process described later.

[0109] (2) Reinforced fiber yarn placement process (first direction) On the non-woven fabric sheet B, rovings of reinforcing fibers that were horizontally drawn out without mixing in a drafting twist were arranged in parallel at -45° with respect to the longitudinal direction (the direction in which the belt conveyor conveys, the 0° direction) and at an areal density of 240 gsm to form a -45° reinforcing fiber sheet. The arrangement of the rovings of the -45° reinforcing fiber sheet was performed by a carriage device. The carriage device in this step reciprocates in the -45° direction, and when it moves forward (or backward) within that, it is a device that arranges the rovings of reinforcing fibers on the belt conveyor. It was controlled so that the rovings of reinforcing fibers 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.

[0110] (3) Arrangement step of rovings of reinforcing fibers (second direction) A second non-woven fabric sheet B was placed on the -45° sheet, and on top of that, in the same manner as the formation, rovings of reinforcing fibers were arranged in parallel at +45° with respect to the longitudinal direction and at an areal density of 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. 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.

[0111] (4) Integration step Subsequently, the laminate on the belt conveyor formed as described above was stitched together with stitch yarn A to be integrated into a reinforcing fiber base material [1]. In such stitching, the stitch yarn A was unwound by an unwinding device and knitted while passing a 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 B had excellent needle penetration, and the fibers of the non-woven fabric did not get caught on the needle.

[0112] (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°, and the fixing method of the stitch yarn was tricot knitting.

[0113] (Example 3) A 1m-wide reinforced fiber base material [3] was created in the same procedure as in Example 1, except that non-woven fabric sheet C was used instead of non-woven fabric sheet B.

[0114] (Example 4) A 1m-wide reinforced fiber base material [4] was produced in the same procedure as in Example 2, except that non-woven fabric sheet C was used instead of non-woven fabric sheet B.

[0115] (Example 5) A 1m-wide reinforced fiber base material [5] was created in the same procedure as in Example 3, except that stitch thread B was used instead of stitch thread A.

[0116] (Example 6) A 1m-wide reinforced fiber base material [1] was produced in the same procedure as in Example 4, except that stitch thread B was used instead of stitch thread A.

[0117] (Reference Example 1) A 1m-wide reference reinforced fiber base material [1´] was created in the same procedure as in Example 1, except that non-woven fabric sheet D was used instead of non-woven fabric sheet B.

[0118] (Comparative Example 1) A 1m-wide comparative reinforced fiber base material [1c] was produced in the following procedure.

[0119] (1) Non-woven fabric placement process The non-woven fabric sheet A without the binder fixed 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 (1m / min in this example) in its longitudinal direction (0° direction) during the subsequent lamination of the reinforced fiber sheet and the non-woven fabric sheet, and was continuously conveyed to the integration process described later.

[0120] (2) Reinforced fiber yarn placement process (first direction) On the nonwoven fabric sheet B, the reinforcing fiber yarns were unwound transversely without mixing in the unwound twist, and arranged parallel to the longitudinal direction (the direction of conveyor belt transport, 0° direction) at -45° and at 240 gsm to form a -45° reinforcing fiber sheet. The reinforcing fiber yarns of the -45° reinforcing fiber sheet were arranged by a carriage device. The carriage device in this process reciprocates in the -45° direction, and is a device that arranges the reinforcing fiber yarns on the belt conveyor during the forward movement (or return movement) of the reinforcing fiber yarns. The carriage device was controlled to align with the speed of the belt conveyor transporting in the longitudinal direction so that the reinforcing fiber yarns do not overlap each other and are arranged next to each other in order.

[0121] (3) Reinforcement fiber yarn arrangement process (second direction) A second nonwoven fabric sheet A is placed on top of the -45° sheet, and a -45° sheet A is placed on top of that. Using the same method as in the formation, the reinforcing fiber yarns were arranged parallel to the longitudinal direction at +45° and at 240 gsm to form a +45° reinforcing fiber sheet, thereby producing a laminate of (nonwoven fabric sheet A / -45° reinforcing fiber sheet / nonwoven fabric sheet A / +45° reinforcing fiber sheet).

[0122] (4) Integration process Next, the laminate on the belt conveyor formed as described above was stitched together with stitch thread A to form a comparative reinforcing fiber substrate [1]. In this stitching, stitch thread A was unwound by a winding device, and needles were knitted while penetrating the laminate. The stitch thread was fixed by chain knitting, with a stitch length of 3 mm and a gauge length of 5 mm. Nonwoven fabric sheet A had excellent needle penetrability, and the fibers of the nonwoven fabric were not entangled with the needles.

[0123] Comparative Example 2 A 1 m wide reinforcing fiber substrate [2c] was produced using the same procedure as in Comparative Example 1, except that the first direction was set to 0°, the second direction was set to 90°, and the stitch thread was fixed using tricot knitting.

[0124] Comparative Example 3 On the surface where the non-woven fabric of the comparative reinforcing fiber base material [1c] is not arranged, the resin material A for preform was dropped while being measured so that the mass per unit area was 20 gsm using an embossing roll and a doctor blade, and was uniformly dispersed. Subsequently, the resin material A for preform was fixed onto the comparative reinforcing fiber base material [1c] by passing it under an 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, and a comparative reinforcing fiber base material [3c] in which the resin material A for preform was fixed to the reinforcing fiber was produced.

[0125] (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 changed to the comparative reinforcing fiber base material [2c].

[0126] ≪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 (bulging), (iv) complex shape formability (stitch breakage), and (v) preform conveyability. Therefore, using the reinforcing 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.

[0127] The characteristic evaluation method of the reinforcing fiber base material and the evaluation methods of (i) to (v) above are shown below.

[0128] (Initial shear rigidity of the reinforcing fiber base material) Three test pieces were cut out for all in-plane directions in which the reinforcing fiber base material could be shear-deformed so that the ends of the non-woven fabric sheet were not included from each reinforcing fiber base material, and a bias extension test was performed to obtain the average value of the initial shear rigidity K.

[0129] (Bending characteristics) Six test pieces were cut out from each reinforced fiber base material so that the ends of the non-woven fabric sheet were not included, with 0°, 45°, 90°, and 135° in the longitudinal direction, and three-point bending tests were performed three times under the condition of bending so that one surface and the other surface contacted the upper jig fulcrum respectively. The average value of the peak load P of each of the eight bending tests was obtained, and the minimum and maximum values among them were obtained.

[0130] (Laminating 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 ends of the non-woven fabric sheet were not included, with 0° and 45° in the longitudinal direction. Subsequently, two test pieces were laminated so that the entire surfaces 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 reinforcing 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 was [-45° / 45° / 0° / 90°].

[0131] In this series of operations, the lamination workability was evaluated in five stages shown in A to E below, and C or above was considered qualified. A: There is no change in the projected area of the reinforced fiber base material before and after lamination, and there is no change in the stitch length and gauge length in all the reinforced fiber base materials. B: There is no change in the projected area of the reinforced fiber base material before and after lamination, but there is a change in either the stitch length or the gauge length in one reinforced fiber sheet. C: There is no change in the projected area of the reinforced fiber base material before and after lamination, but there is a change in either the stitch length or the gauge length in two reinforced fiber sheets. D: There is a change in the projected area of the reinforced fiber base material before and after lamination, and there is a change in either the stitch length or the gauge length in one reinforced fiber sheet. E: There is a change in the projected area of the reinforced fiber base material before and after lamination, and there is a change in either the stitch length or the gauge length in two reinforced fiber sheets.

[0132] The projected area is the value obtained by multiplying the length and width of the reinforced fiber base material. The length and width of the reinforced fiber base material are measured to the nearest 0.1 mm using a ruler. No change in the projected area 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 reinforced fiber base material on one side of the reinforced fiber base material, the length of 50 repeating units (any length less than 50 repeating units is rounded down) from one end to the other end of the reinforced 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.

[0133] (Complex shape conformability) The conformability of the reinforced fiber base material to a complex shape was evaluated using an aluminum shaping jig with a length of 1100 mm, a width of 90 mm, and a height (depth in the paper plane of Fig. 6) of 70 mm shown in Fig. 6. 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. 7. 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. 8, 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 conform to 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.

[0134] 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 designated as A; when a slight bulge occurred, it was designated as B; and when a bulge of medium or greater degree that affects injection molding occurred, it was designated as C. A or above 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.

[0135] (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 the five levels shown in A to E below, and C or above was considered a pass. A: After transport, the layers between 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 between 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 between 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 between the reinforcing fiber sheets constituting the laminated body after transport. E: The reinforcing fiber substrate became separated and could not be handled as a preform.

[0136] As a result of the above evaluations, the reinforced fiber base materials [1] to [6] shown in the examples exhibited excellent formability and shape stability. Therefore, they were excellent in lamination 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 reinforced fiber base materials [5] and [6] shown in Examples 5 and 6 did not cause stitch breakage when formed into complex shapes, and were reinforced fiber base materials capable of obtaining preforms with particularly excellent quality.

[0137] Also, the reinforced fiber base material shown in Reference Example [1'] was excellent in lamination workability, did not cause wrinkles or bulges even when formed into complex shapes, and exhibited excellent formability. However, the ratio of the surface of the non-woven fabric sheet coated with the resin material for the preform was smaller than that of the other examples, and the reinforced fiber base material was partially peeled off during preform transport, causing disorder in the reinforced fiber yarns.

[0138] On the other hand, although the comparative reinforced 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 lamination workability and caused disorder in the reinforced fiber yarns. Furthermore, they could not maintain the three-dimensional shape of the preform. Also, although the comparative reinforced fiber base materials [3c] and [4c] shown in Comparative Examples 3 and 4 had their shapes maintained by the resin material for the preform and were excellent in lamination workability, they had large wrinkles and bulges when formed into complex shapes, resulting in inferior formability.

[0139]

Table 1

[0140]

Table 2

Industrial Applicability

[0141] 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 use such as windmill blades.

Explanation of reference numerals

[0142] 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 obtained by laminating one or more reinforced fiber sheets with nonwoven fabric sheets, in which the nonwoven fabric sheets are arranged on one or both sides of a reinforced fiber sheet formed by aligning reinforcing fiber yarns in parallel and fixing them with stitch yarns, where (a) the nonwoven fabric sheet is arranged on at least one outermost surface of the reinforced fiber base material, and (b) a resin material for preform is fixed to the entire surface of the fibers constituting the nonwoven fabric sheet arranged on the outermost surface. (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, characterized by a reinforced fiber substrate.

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

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

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

8. The reinforced fiber base material according to claim 7, wherein the average particle diameter of the resin material for preform 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 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.

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

11. Among the reinforced fiber sheets with nonwoven fabric laminated in multiple layers, it includes 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, and the first direction and the second direction are orthogonal to each other. The reinforced fiber base material according to claim 1.

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