Fiber structure and fiber-reinforced composite

Abstract

This fiber structure, which serves as a reinforcing substrate for a fiber-reinforced composite (10) that uses a matrix resin as a base material, comprises a plurality of reinforcing fiber yarns in which a covering yarn is wound around an outer peripheral part of a fiber bundle including discontinuous fibers made of reinforcing fibers, wherein: said fiber structure includes a fiber arrangement portion in which the plurality of reinforcing fiber yarns are arranged so as to extend in the same direction; and when the number of windings of the covering yarn is defined as (T) [T / m], the yarn width of the reinforcing fiber yarn used in the production of said fiber structure is defined as (A) [mm], the yarn width of the reinforcing fiber yarn in the fiber-reinforced composite (10) is defined as (B) [mm], and the pitch between the reinforcing fiber yarns is defined as (P) [mm], the number (T) of windings and the yarn width (A) satisfy the following conditions 1 and 2. (Condition 1) B=A×(-0.0004T+1.6114) (Condition 2) 0.85P≤B≤1.2P

Description

Fiber structure and fiber-reinforced composite material

[0001] The present invention relates to a fiber structure and a fiber-reinforced composite material.

[0002] A fiber-reinforced composite material is manufactured, for example, using a matrix resin as a base material and a fiber structure as a reinforcing base material. Fiber-reinforced composite materials are sometimes required to have high mechanical strength equal to or higher than a predetermined level. As conventional techniques for fiber structures and fiber-reinforced composite materials, for example, the carbon fiber yarn and the manufacturing method therefor disclosed in Patent Document 1 are known. The recycled carbon fiber disclosed in Patent Document 1 is discontinuous fibers extending linearly, and the recycled carbon fiber includes discontinuous carbon fibers.

[0003] Japanese National Publication of International Patent Application No. 2013-519000

[0004] Reinforcing fiber yarn using linearly extending discontinuous fibers needs to maintain its shape as a fiber bundle by winding a covering yarn around a bundle of discontinuous fibers. Therefore, when a fiber structure using reinforcing fiber yarn including covering yarn is used as a reinforcing base material, gaps are easily formed between the reinforcing fiber yarns. As a result, in the fiber-reinforced composite material, besides the tendency for a resin-rich region where only matrix resin is filled between the reinforcing fiber yarns to occur, there is also the problem that voids are likely to form in the resin-rich region. Such resin-rich regions and voids cause a reduction in the physical properties of the fiber-reinforced composite material.

[0005] The present invention has been made in view of the above problems, and an object of the present invention is to provide a fiber structure and a fiber-reinforced composite material capable of suppressing the occurrence of resin-rich regions and voids.

[0006] To solve the above problems, the present invention provides a fiber structure that serves as a reinforcing base material for a fiber-reinforced composite material with a matrix resin as the base material, comprising a plurality of reinforcing fiber yarns in which a covering yarn is wound around the outer circumference of a fiber bundle containing discontinuous reinforcing fibers, and comprising a fiber arrangement portion in which the plurality of reinforcing fiber yarns are arranged to extend in the same direction from one another, wherein when the number of turns of the covering yarn is T [T / m], the yarn width A [mm] of the reinforcing fiber yarn used in the manufacture of the fiber structure is B [mm], the yarn width B of the reinforcing fiber yarn in the fiber-reinforced composite material is P [mm], and the pitch between the reinforcing fiber yarns is P [mm], the number of turns of the covering yarn is T and the yarn width A of the reinforcing fiber yarn before pressurization is satisfied with the following conditions 1 and 2. (Condition 1) B = A × (1.6114 - 0.0004T) (Condition 2) 0.85P ≤ B ≤ 1.2P

[0007] In this invention, the number of turns T of the covering yarn and the yarn width A of the reinforcing fiber yarn before pressurization satisfy conditions 1 and 2. Therefore, when the fiber arrangement area is pressurized in conjunction with the pressurization of the fiber structure, the reinforcing fiber yarn in the fiber arrangement area deforms so that its cross-section becomes flattened without changing the pitch P between the reinforcing fiber yarns. Since the number of turns T of the covering yarn and the yarn width A of the reinforcing fiber yarn used in the manufacture of the fiber structure satisfy conditions 1 and 2, the gaps between the reinforcing fiber yarns after pressurization are almost eliminated. As a result, the occurrence of resin richness and voids can be suppressed in fiber-reinforced composite materials using a matrix resin as the base material with a fiber structure. Furthermore, the number of turns T of the covering yarn is a number of turns that does not hinder the deformation of the reinforcing fiber yarn due to pressurization. Therefore, it is possible to achieve both the ease of deformation of the reinforcing fiber yarn and the prevention of fiber bundle detachment by the covering yarn. As a result, the mechanical strength and elastic modulus of fiber-reinforced composite materials using a matrix resin as the base material with a fiber structure can be improved.

[0008] Furthermore, in the above-described fiber structure, when the width of the covering yarn is D [mm], the number of turns T and the yarn width A may be configured to satisfy the following condition 3. (Condition 3) P - 2D ≤ B ≤ P In this case, the number of turns T and the yarn width A satisfy the following condition 3, so that the gaps between the reinforcing fiber threads after pressurization are reduced, making it less likely for resin-rich or porous materials to occur in the fiber-reinforced composite material using a matrix resin with a fiber structure as the base material.

[0009] Furthermore, in the above-described fiber structure, the fiber bundle may include carbon fibers. In this case, since the fiber bundle includes carbon fibers, the mechanical strength and elasticity of the fiber-reinforced composite material will not be reduced.

[0010] Furthermore, in the above-described fiber structure, the covering yarn may be made of organic fibers. In this case, since organic fibers are more flexible than inorganic fibers, it becomes easier to wrap the covering yarn around the outer circumference of the fiber bundle containing discontinuous fibers. Also, when a fiber-reinforced composite material is manufactured by impregnating and curing a matrix resin into the fiber structure, the covering yarn and the matrix resin have a high affinity, which tends to increase the mechanical strength and elasticity of the fiber-reinforced composite material.

[0011] Furthermore, the fiber arrangement portion may be configured as a unidirectional woven fabric formed by the plurality of reinforcing fibers. In this case, since the fiber arrangement portion is a unidirectional woven fabric formed by the plurality of reinforcing fibers, the reinforcing fiber yarn around which the covering yarn is wrapped becomes more susceptible to deformation under pressure.

[0012] Furthermore, the present invention relates to a fiber-reinforced composite material in which a matrix resin is used as the base material and a fiber structure is used as the reinforcing base material, wherein the fiber structure is the fiber structure described above. In the present invention, a fiber-reinforced composite material can be obtained in which resin richness and void generation are suppressed.

[0013] According to the present invention, it is possible to provide a fiber structure and a fiber-reinforced composite material that can suppress the occurrence of resin-richness and voids.

[0014] This is a schematic perspective view showing a fiber-reinforced composite material according to an embodiment of the present invention. This is a schematic longitudinal cross-sectional view showing a fiber structure before pressurization according to an embodiment of the present invention. This is a schematic perspective view showing the warp threads in a fiber structure according to an embodiment of the present invention. This is a schematic perspective view showing the weft threads in a fiber structure according to an embodiment of the present invention. This is a schematic longitudinal cross-sectional view showing a fiber-reinforced composite material according to an embodiment of the present invention. This is an explanatory diagram showing the calculated values ​​of the yarn width change rate with respect to the number of turns of the weft and covering threads used in the experiment. This is an explanatory diagram explaining the relationship between the number of turns of the covering thread and the yarn width change rate.

[0015] Hereinafter, a fiber structure and fiber-reinforced composite material according to embodiments of the present invention will be described with reference to the drawings. First, the fiber structure will be described, but in the following description, the fiber structure will be described assuming that it is placed horizontally. In the drawings, the direction along the horizontal plane is indicated by the X axis and Y axis, and the direction perpendicular to the horizontal plane is indicated by the Z axis. The X axis, Y axis and Z axis are orthogonal to each other. The direction parallel to the X axis is also called the first direction X. The direction parallel to the Y axis is also called the second direction Y. The second direction Y is perpendicular to the first direction X. The lamination direction Z is the direction parallel to the Z axis.

[0016] As shown in Figure 1, the fiber-reinforced composite material 10 is constructed by impregnating a fiber structure 11 with a matrix resin M as a matrix material. The fiber structure 11 is the reinforcing base material of the fiber-reinforced composite material 10. The matrix resin M, which serves as the base material, is, for example, a thermosetting resin. Examples of thermosetting resins include epoxy resins, vinyl ester resins, unsaturated polyester resins, and phenolic resins. The fiber-reinforced composite material 10 is formed by impregnating the fiber structure 11 with a thermosetting resin using the RTM (Resin Transfer Molding) method.

[0017] As shown in Figure 2, the fiber structure 11 is a precursor before being impregnated in the matrix resin M and sintered. The fiber structure 11 comprises a plurality of warp layers 12 as first yarn layers and a plurality of weft layers 13 as second yarn layers. Each of the plurality of warp layers 12 and the plurality of weft layers 13 is laminated in the lamination direction Z. Multiple warp threads 14, which are first reinforcing fiber threads used in the manufacture of the fiber structure 11, are arranged in the second direction Y in the warp layer 12. The main axis of the warp threads 14 extends in the first direction X. Multiple weft threads 15, which are second reinforcing fiber threads used in the manufacture of the fiber structure 11, are arranged in the first direction X in the weft layer 13. The main axis of the weft threads 15 extends in the second direction Y. The direction in which the warp threads 14 extend and the direction in which the weft threads 15 extend intersect. The warp layer 12 and the weft layer 13 correspond to fiber arrangement sections in which multiple reinforcing fiber threads are arranged to extend in the same direction from one another. When distinguishing between the fiber arrangement sections, the warp layer 12 is referred to as the first fiber arrangement section, and the weft layer 13 as the second fiber arrangement section.

[0018] The warp threads 14 are, for example, continuous threads made by bundling together multiple reinforcing fibers. Specifically, as shown in Figure 3, they are formed by bundling together continuous fibers 16 made of reinforcing fibers. The continuous fibers 16 are linear and have straightness. Note that having linearity means that they are linear as a whole, but may include some curvature or twisting.

[0019] Since the warp threads 14 are formed by bundling linearly extending continuous fibers 16, a slight twist is added to the fiber bundles of the continuous fibers 16 in order to maintain the shape of the thread. As the continuous fibers 16, organic fibers or inorganic fibers may be used, or different types of organic fibers, different types of inorganic fibers, or blended fibers made by blending organic and inorganic fibers may be used. Examples of organic fibers include acrylic fibers, nylon fibers, polyester fibers, aramid fibers, poly-p-phenylenebenzobisoxazole fibers, and ultra-high molecular weight polyethylene fibers. Examples of inorganic fibers include carbon fibers, glass fibers, and ceramic fibers. In this embodiment, the continuous fibers 16 are long carbon fibers as inorganic fibers.

[0020] As shown in Figure 4, the weft yarn 15 is a spun yarn consisting of a fiber bundle containing discontinuous fibers 17, and corresponds to a reinforced fiber yarn. The weft yarn 15 is formed by spirally winding a covering yarn 18 around the outer circumference of a fiber bundle containing discontinuous fibers 17 made of reinforced fibers. The covering yarn 18 maintains the shape of the fiber bundle of discontinuous fibers 17 in a thread-like form. The discontinuous fibers 17 are short fibers. The discontinuous fibers 17 are formed by cutting long fibers. The discontinuous fibers 17 are shorter than the continuous fibers 16 of the warp yarn 14.

[0021] The continuous fibers 16 and discontinuous fibers 17 may be organic fibers or inorganic fibers, or different types of organic fibers, different types of inorganic fibers, or blended fibers obtained by blending organic and inorganic fibers may be used. Examples of organic fibers include acrylic fibers, nylon fibers, polyester fibers, aramid fibers, poly-p-phenylenebenzobisoxazole fibers, and ultra-high molecular weight polyethylene fibers, while examples of inorganic fibers include carbon fibers, glass fibers, and ceramic fibers. The weft yarn 15 in this embodiment is a spun yarn mainly containing carbon fibers.

[0022] The cross-sectional shape of the weft yarn 15 is maintained in a nearly circular shape by the spiral winding of the covering yarn 18. The weft yarn 15 is formed with the fiber orientation of the discontinuous fibers 17 aligned in one direction. The covering yarn 18 is made of organic fiber. As the material for the covering yarn 18, an organic fiber is selected that has a melting point such that the covering yarn 18 does not melt when the fiber structure 11 is heated during the manufacture of the fiber-reinforced composite material 10. In this embodiment, the covering yarn 18 is nylon fiber.

[0023] The fiber structure 11 is formed by joining two stacked fabrics in the stacking direction Z with interlayer bonding threads 19 (see Figure 2). In other words, the fiber structure 11 is manufactured by joining two stacked fabrics in the stacking direction Z with interlayer bonding threads 19. Each of the two fabrics comprises two warp layers 12 and one weft layer 13. In this embodiment, one weft layer 13 is sandwiched between two warp layers 12.

[0024] The interlayer bonding yarn 19 extends in the lamination direction Z of the warp layer 12 and the weft layer 13, and is folded back in the outermost warp layer 12 of the fiber structure 11. In the weft layer 13, where the interlayer bonding yarn 19 extends in the lamination direction Z, the weft yarns 15 are slightly separated by the interlayer bonding yarn 19. In the weft layer 13, the weft yarns 15 are adjacent to each other, sandwiching the interlayer bonding yarn 19 that extends in the lamination direction Z. In other words, some of the weft yarns 15 are separated by the interlayer bonding yarn 19.

[0025] Prior to the manufacture of the fiber-reinforced composite material 10, the fiber structure 11 is pressed in the lamination direction. The fiber structure 11 is pressed, for example, by a press machine. As shown in Figure 2, in the fiber structure 11 before pressing, the cross-section of the weft yarn 15 is approximately circular. In the pressed fiber structure 11, the cross-section of the weft yarn 15 becomes elliptical. The fiber-reinforced composite material 10 is formed after the fiber structure 11 has been pressed by the RTM method, using the pressed fiber structure 11 as the reinforcing base material. The cross-section of the weft yarn 15 in the pressed fiber structure 11 is approximately the same as the cross-section of the weft yarn 15 in the fiber-reinforced composite material 10 shown in Figure 5. As shown in Figure 5, the fiber-reinforced composite material 10 is manufactured by filling a mold 20 in which the fiber structure 11 is placed with matrix resin M. When the matrix resin M is filled into the mold 20, the matrix resin M filled into the mold 20 is impregnated into the fiber structure 11 by the filling pressure. Note that, for the sake of clarity, the covering yarn 18 and interlayer bonding yarn 19 are not shown in Figure 5.

[0026] In the warp layer 12 and weft layer 13 of the fiber structure 11, the matrix resin M is impregnated into each warp thread 14 and each weft thread 15, and the matrix resin M is impregnated into the entire fiber structure 11. In the warp layer 12, the matrix resin M fills the spaces between adjacent warp threads 14. Similarly, in the weft layer 13, the matrix resin M fills the spaces between adjacent weft threads 15. When the matrix resin M and the fiber structure 11 are heated in the mold 20, the matrix resin M hardens and the matrix resin M is compounded. As a result, a fiber-reinforced composite material 10 is manufactured, with the matrix resin M as the base material and the fiber structure 11 as the reinforcing base material.

[0027] By the way, the fiber structure 11 shown in Figure 2 is in its pre-pressurized state, while in the fiber-reinforced composite material 10 shown in Figure 5, the fiber structure 11 is in a pressurized state. The yarn width A [mm] of the weft yarn 15 used in the manufacture of the fiber structure 11 is denoted as B [mm] of the weft yarn 15 in the fiber-reinforced composite material 10. The pitch P [mm] of adjacent weft yarns 15 is denoted as T [T / m] of the covering yarn 18, and the yarn width D [mm] of the covering yarn 18 is denoted as D [mm].

[0028] The yarn widths A and B are the lengths in the first direction X perpendicular to the pressurizing direction in the cross-section of the weft yarn 15, and the rate of change of yarn widths A and B before and after pressurizing can be expressed as the yarn width change rate (B / A). The pitch P is a design value according to the type of fiber-reinforced composite material 10, and the pitch P of the fiber structure 11 in the fiber structure 11 in the fiber-reinforced composite material 10 before and after pressurizing is basically unchanged. The number of turns T is expressed as the number of turns per meter. The weft yarn 15 becomes less susceptible to deformation by pressurizing as the number of turns T increases, and more susceptible to deformation by pressurizing as the number of turns T decreases. If the number of turns T becomes too small, discontinuous fibers 17 tend to come out of the weft yarn 15. The weft yarn 15 becomes less susceptible to deformation by pressurizing as the yarn width D of the covering yarn 18 increases, and more susceptible to deformation by pressurizing as the yarn width D of the covering yarn 18 decreases.

[0029] In this embodiment, as shown in Figure 6, multiple weft threads 15 were prepared by changing the number of turns T, using a carbon fiber weft thread 15 with a width of 200 [mm] and a nylon covering thread 18 with a width of 5.5 [mm]. The thread widths A and B of each weft thread 15 were measured and the thread width change rate (B / A) was calculated.

[0030] The measurement results are shown in Figure 6. For weft yarn 15 with 410 turns [T / m], the yarn width change rate (B / A) was 1.42. For weft yarn 15 with 233 turns [T / m], the yarn width change rate (B / A) was 1.54. For weft yarn 15 with 489 turns [T / m], the yarn width change rate (B / A) was 1.43. For weft yarn 15 with 278 turns [T / m], the yarn width change rate (B / A) was 1.52. For weft yarn 15 with 167 turns [T / m], the yarn width change rate (B / A) was 1.55. For weft yarn 15 with 704 turns [T / m], the yarn width change rate (B / A) was 1.36. With a weft yarn of 15 with a winding count of 400 [T / m], the yarn width change rate (B / A) was 1.47. With a weft yarn of 15 with a winding count of 240 [T / m], the yarn width change rate (B / A) was 1.52.

[0031] Figure 7 is an explanatory diagram showing the relationship between the number of turns T and the yarn width change rate (B / A). In Figure 7, the yarn width change rate (B / A) calculated in relation to the number of turns T is plotted as black circles. Applying the least squares method as a regression analysis to the multiple black circle plots shown in Figure 7 yields Condition 1 shown below. Condition 1 is a condition derived based on a linear function of the yarn width B after pressurization, with the number of turns T as the variable. (Condition 1) B = A × (-0.0004T + 1.6114)

[0032] Furthermore, in this embodiment, the following condition 2 was obtained, which shows the relationship between the yarn width B and pitch P of the weft yarn 15 in the fiber-reinforced composite material 10. (Condition 2) 0.85P ≤ B ≤ 1.2P

[0033] Condition 2 defines the range of yarn width B after pressurization. If the yarn width B is less than 0.85P, the gaps between adjacent weft threads 15 in the fiber-reinforced composite material 10 become larger, resulting in resin-rich areas and voids. Resin-rich areas are areas where the matrix resin M is unevenly concentrated, and voids are phenomena where the matrix resin M is absent, both of which reduce the mechanical strength and elastic modulus of the fiber-reinforced composite material 10. On the other hand, if the yarn width B exceeds 1.2P, the deformation of the weft threads 15 is hindered when the fiber structure 11 is pressed. Condition 2 is a preferred range for yarn width B and is a condition obtained from the inventors' findings based on their tests.

[0034] In this embodiment, when the number of turns T and the yarn width A satisfy conditions 1 and 2, the areas where the matrix resin M fills between adjacent weft threads 15 when the fiber structure 11 is pressed are reduced, making it less likely for resin-rich or void material to occur in the fiber-reinforced composite material 10. This ensures the mechanical strength and elastic force required for the fiber-reinforced composite material 10.

[0035] Furthermore, in this embodiment, the following condition 3 was obtained from the inventors' test findings as a more preferred range for the yarn width B: (Condition 3) P - 2D ≤ B ≤ P

[0036] Condition 3 defines a more preferable range for the yarn width B after pressurization, and is determined in relation to the yarn width D of the covering yarn 18. When the number of turns T and yarn width A satisfy conditions 1 and 3, the areas where the matrix resin M is filled between adjacent weft yarns 15 during pressurization of the fiber structure 11 are further reduced, making it even less likely for resin-rich or voided areas to occur in the fiber-reinforced composite material 10. This improves the mechanical strength and elasticity required for the fiber-reinforced composite material 10.

[0037] The fiber structure 11 and fiber-reinforced composite material 10 according to this embodiment have the following effects: (1) The number of turns T of the covering yarn 18 and the yarn width A of the weft yarn 15 used in the manufacture of the fiber structure 11 satisfy conditions 1 and 2. Therefore, when the weft layer 13 is pressurized in conjunction with the pressurization of the fiber structure 11, each weft yarn 15 in the weft layer 13 deforms so that its cross-section becomes flattened without changing the pitch P between the weft yarns 15. Since the number of turns T of the covering yarn 18 and the yarn width A of the weft yarn 15 before pressurization satisfy conditions 1 and 2, the gaps between the weft yarns 15 after pressurization are almost eliminated. As a result, the occurrence of resin richness can be suppressed in the fiber-reinforced composite material 10 using the fiber structure 11 as the base material and matrix resin M. In addition, the number of turns T of the covering yarn 18 is a number of turns that does not hinder the deformation of the weft yarn 15 due to pressurization. Therefore, it is possible to achieve both the ease of deformation of the weft yarn 15 and the prevention of discontinuous fibers 17 falling off in the fiber bundle by the covering yarn 18. As a result, it is possible to improve the mechanical strength and elastic modulus of the fiber-reinforced composite material 10, which uses the fiber structure 11 as the base material and a matrix resin M.

[0038] (2) Since the number of turns T and the yarn width A satisfy condition 3, the gaps between the weft threads 15 after pressurization are reduced, making it less likely for resin-rich or porous materials to occur in the fiber-reinforced composite material 10 which has a matrix resin M using the fiber structure 11 as the base material.

[0039] (3) Since the fiber bundle of the weft 15 contains carbon fibers, it does not reduce the mechanical strength and elasticity of the fiber-reinforced composite material 10.

[0040] (4) The covering yarn 18 is a continuous yarn made of organic fibers. Since organic fibers are more flexible than inorganic fibers, it is easier to wrap the covering yarn 18 around the outer circumference of the fiber bundle containing the discontinuous fibers 17. Furthermore, the fiber-reinforced composite material 10 is manufactured by impregnating and curing the fiber structure 11 with the matrix resin M, and the covering yarn 18 and the matrix resin M have a high affinity, making it easy to improve the mechanical strength and elasticity of the fiber-reinforced composite material 10.

[0041] (5) Since the weft layer 13, which is the fiber arrangement section, is a unidirectional fabric formed by multiple weft threads 15, the weft threads 15 around which the covering threads 18 are wrapped are easily deformed by pressure.

[0042] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the invention. For example, the following modifications may be made.

[0043] ○ In the above embodiment, the warp layer as the first yarn layer used continuous fibers for the warp, but is not limited to this. The warp layer as the first yarn layer may be a spun yarn consisting of fiber bundles containing discontinuous fibers, for example, as the weft as the second yarn layer. In this case, covering yarn may be wrapped around the fiber bundles of the warp. ○ In the above embodiment, the weft layer as the second yarn layer used one covering yarn wrapped around the fiber bundles of the weft, but is not limited to this. For example, there may be multiple covering yarns wrapped around the fiber bundles of the weft. ○ In the above embodiment, the covering yarn was made of organic fibers, but is not limited to this. For example, the covering yarn may be made of inorganic fibers. ○ In the above embodiment, the matrix resin was a thermosetting resin, but is not limited to this. The matrix resin may be a thermoplastic resin such as polyamide, polybutylene terephthalate, polycarbonate, polyethylene, polypropylene, polyimide resin, ABS resin, etc. ○ In the above embodiment, the fiber bundles in the weft as the first reinforcing fiber yarn were not twisted, but is not limited to this. The fiber bundles of discontinuous fibers in the weft may be twisted. In this case, the twisting of the fiber bundles of discontinuous fibers and the winding of the covering yarn can reliably suppress the detachment of discontinuous fibers from the weft. ○ In the above embodiment, a unidirectional woven fabric was used as an example to describe the fiber structure, but it is not limited thereto. The fiber structure may be, for example, a multilayer woven fabric other than a unidirectional woven fabric. ○ In the above embodiment, the fiber structure was a fiber structure for manufacturing a fiber-reinforced composite material by the RTM method, but it is not limited thereto. The fiber structure may be a fiber structure using a prepreg sheet material comprising fiber bundles impregnated with matrix resin.

[0044] 10 Fiber-reinforced composite material 11 Fiber structure 12 Warp layer (first fiber arrangement) 13 Weft layer (second fiber arrangement) 14 Warp (first reinforcing fiber yarn) 15 Weft (second reinforcing fiber yarn) 16 Continuous fiber 17 Discontinuous fiber 18 Covering yarn 19 Interlayer bonding yarn 20 Molding mold A Width of weft yarn before pressurization B Width of weft yarn after pressurization D Width of covering yarn P Pitch of weft yarn T Number of turns of covering yarn M Matrix resin X First direction Y Second direction Z Lamination direction (pressurization direction)

Claims

1. A fiber structure that serves as a reinforcing base material for a fiber-reinforced composite material with a matrix resin as the base material, comprising a plurality of reinforcing fiber yarns in which covering yarn is wound around the outer circumference of a fiber bundle containing discontinuous reinforcing fibers, and comprising a fiber arrangement portion in which the plurality of reinforcing fiber yarns are arranged to extend in the same direction from one another, wherein when the number of turns of the covering yarn is T [T / m], the yarn width A [mm] of the reinforcing fiber yarn used in the manufacture of the fiber structure, the yarn width B [mm] of the reinforcing fiber yarn in the fiber-reinforced composite material, and the pitch P [mm] between the reinforcing fiber yarns, the number of turns T and the yarn width A satisfy the following conditions 1 and 2. (Condition 1) B = A × (-0.0004T + 1.6114) (Condition 2) 0.85P ≤ B ≤ 1.2P 2. The fiber structure according to claim 1, characterized in that, when the width of the covering yarn is D [mm], the number of turns T and the yarn width A satisfy the following condition 3. (Condition 3) P - 2D ≤ B ≤ P 3. The fiber structure according to claim 1 or 2, characterized in that the fiber bundle includes carbon fibers.

4. The fiber structure according to claim 1 or 2, characterized in that the covering yarn is made of organic fibers.

5. The fiber structure according to claim 1 or 2, characterized in that the fiber arrangement portion is a unidirectional woven fabric formed by the plurality of reinforcing fiber threads.

6. A fiber-reinforced composite material having a matrix resin as the base material and a fiber structure as the reinforcing base material, wherein the fiber structure is the fiber structure described in claim 1 or 2.

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