Fiber structures and fiber-reinforced composites

Abstract

To provide a fiber structure and a fiber-reinforced composite material capable of suppressing generation of resin-rich.SOLUTION: A fiber structure 20 comprises a first reinforcing fiber yarn 31 having a covering yarn 33 wound around the periphery of a fiber bundle including discontinuous fibers 32 made of a reinforcing fiber, and a second reinforcing fiber yarn 21 formed by bundling continuous fibers 22 made of a reinforcing fiber. The fiber structure 20 is formed by arranging the first reinforcing fiber yarns 31 and the second reinforcing fiber yarns 21 so as to extend in the same direction. The fiber structure 20 has portions where the second reinforcing fiber yarn 21 is sandwiched between the first reinforcing fiber yarns 31.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] A fiber reinforced composite material has a matrix resin as a base material and a fiber structure as a reinforcing base material. The reinforcing fiber yarns forming the fiber structure are preferably untwisted yarns. This is because when the reinforcing fiber yarns are untwisted yarns, the fiber orientation in the reinforcing fiber yarns tends to be aligned in one direction, so that a decrease in the strength of the fiber reinforced composite material can be suppressed. Examples of the reinforcing fiber forming the untwisted reinforcing fiber yarn include recycled carbon fiber contained in the spun yarn disclosed in Patent Document 1. The recycled carbon fiber disclosed in Patent Document 1 is discontinuous fiber extending linearly.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Reinforcing fiber yarns using discontinuous fibers extending linearly need to maintain the shape as a fiber bundle by winding a covering yarn around the bundle of discontinuous fibers. Therefore, when a fiber structure using a reinforcing fiber yarn containing a covering yarn is used as a reinforcing base material, gaps are likely to be formed between the reinforcing fiber yarns. As a result, in the fiber reinforced composite material, a resin rich portion filled only with the matrix resin between the reinforcing fiber yarns is likely to occur.

Means for Solving the Problems

[0005] The fiber structure for solving the above problems is 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 first reinforcing fiber yarn in which a covering yarn is wrapped around the outer circumference of a fiber bundle containing discontinuous fibers made of reinforcing fibers; and a second reinforcing fiber yarn formed by bundling continuous fibers made of reinforcing fibers, wherein the fiber arrangement portion is formed in which the first reinforcing fiber yarn and the second reinforcing fiber yarn are arranged so as to extend in the same direction, and the fiber arrangement portion comprises a portion in which the second reinforcing fiber yarn is sandwiched by the first reinforcing fiber yarn.

[0006] According to this, when the fiber arrangement area is pressurized along with the pressurization of the fiber structure, the first reinforcing fiber yarns in the fiber arrangement area either maintain their shape or deform slightly due to the covering yarns. On the other hand, in the fiber arrangement area, the second reinforcing fiber yarns deform due to the pressurization, causing the spacing between continuous fibers to widen. As a result, continuous fibers are dispersed between the first reinforcing fiber yarns that were sandwiching the second reinforcing fiber yarns. Therefore, in a fiber-reinforced composite material using a fiber structure as the reinforcing base material, continuous fibers are dispersed in the matrix resin filled between the first reinforcing fiber yarns. Consequently, the occurrence of resin richness between the first reinforcing fiber yarns in the fiber-reinforced composite material can be suppressed.

[0007] With respect to the fiber structure, the fiber structure may be a unidirectional fabric in which the entire fiber structure is the fiber arrangement portion. According to this, in unidirectional woven fabrics, the second and first reinforcing fibers tend to align randomly when the fiber structure is compressed, making it easier for the second reinforcing fibers to be positioned between the first reinforcing fibers. Therefore, continuous fibers tend to disperse between the first reinforcing fibers when the fiber structure is compressed. Thus, fiber structures made of unidirectional woven fabrics tend to suppress the formation of resin richness between the first reinforcing fibers.

[0008] Regarding the fiber structure, the fiber structure is a woven fabric comprising a warp layer made of warp threads and a weft layer made of weft threads, the fiber arrangement portion being the warp layer, and the warp layer may comprise the first reinforcing fiber yarn and the second reinforcing fiber yarn as the warp threads.

[0009] According to this, even in woven fabrics, it is possible to suppress the occurrence of resin-rich areas where only matrix resin exists between the first reinforcing fiber threads. The fiber-reinforced composite material for solving the above problems is a fiber-reinforced composite material that uses a matrix resin as the base material and a fiber structure as the reinforcing base material, wherein the fiber structure comprises a first reinforcing fiber yarn in which a covering yarn is wrapped around the outer circumference of a fiber bundle containing discontinuous fibers made of reinforcing fibers, and a second reinforcing fiber yarn formed by bundling continuous fibers made of reinforcing fibers, and comprises a fiber arrangement portion formed in which the first reinforcing fiber yarn and the second reinforcing fiber yarn are arranged so as to extend in the same direction, the fiber arrangement portion comprises a portion in which the second reinforcing fiber yarn is sandwiched by the first reinforcing fiber yarn, and the continuous fibers are dispersed in the matrix resin filled between the first reinforcing fiber yarns.

[0010] According to this, when the fiber arrangement area is pressurized along with the pressurization of the fiber structure, the first reinforcing fiber yarns in the fiber arrangement area either maintain their shape or deform slightly due to the covering yarns. On the other hand, in the fiber arrangement area, the second reinforcing fiber yarns deform due to the pressurization, causing the spacing between continuous fibers to widen. As a result, continuous fibers are dispersed between the first reinforcing fiber yarns that were sandwiching the second reinforcing fiber yarns. Therefore, in a fiber-reinforced composite material using a fiber structure as the reinforcing base material, continuous fibers are dispersed in the matrix resin filled between the first reinforcing fiber yarns. Consequently, the occurrence of resin richness between the first reinforcing fiber yarns in the fiber-reinforced composite material can be suppressed. [Effects of the Invention]

[0011] This invention can suppress the occurrence of resin-rich material. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a schematic cross-sectional view of a fiber-reinforced composite material. [Figure 2] Figure 2 is a schematic cross-sectional view showing the fibrous structure. [Figure 3] Figure 3 is a schematic diagram showing the second reinforcing fiber yarn. [Figure 4] Figure 4 is a schematic diagram showing the first reinforcing fiber yarn. [Figure 5] Figure 5 is a schematic diagram of a pultrusion apparatus. [Figure 6] Figure 6 is a schematic cross-sectional view showing another example of a fibrous structure. [Figure 7] Figure 7 is a schematic cross-sectional view showing another example of a fiber-reinforced composite material. [Modes for carrying out the invention]

[0013] (First embodiment) The first embodiment of the fiber structure and fiber-reinforced composite material will be described below with reference to Figures 1 to 5. Figure 1 schematically shows the fiber-reinforced composite material 10 and the fiber structure 20. Figure 2 schematically shows the fiber structure 20. Figure 3 schematically shows the second reinforcing fiber yarn 21. Figure 4 schematically shows the first reinforcing fiber yarn 31.

[0014] <Fiber-reinforced composite material> As shown in Figure 1, the fiber-reinforced composite material 10 uses a matrix resin 12 as the base material and a fiber structure 20 as the reinforcing base material. The fiber structure 20 is the reinforcing base material of the fiber-reinforced composite material 10, which uses the matrix resin 12 as the base material. In Figure 1, the fiber-reinforced composite material 10 is shown schematically, so the matrix resin 12 is shown with dot hatching, and detailed illustrations of the external shapes of the fiber-reinforced composite material 10 and the fiber structure 20 are omitted.

[0015] The fiber reinforced composite material 10 is a square columnar prepreg. Note that the shapes of the fiber structure 20 and the fiber reinforced composite material 10 can be arbitrarily columnar with an H-shaped cross section, columnar with a U-shaped cross section, or tubular. The matrix resin 12 uses an epoxy resin, which is a thermosetting resin. Note that the matrix resin 12 does not have to be an epoxy resin, and may be a thermosetting resin such as a vinyl ester resin, an unsaturated polyester resin, or a phenol resin, or may be a thermoplastic resin such as a polyamide, polybutylene terephthalate, polycarbonate, polyethylene, polypropylene, polyimide resin, or ABS resin.

[0016] <Fiber structure> As shown in FIG. 2, the fiber structure 20 includes a plurality of first reinforcing fiber yarns 31 and a plurality of second reinforcing fiber yarns 21. In FIGS. 1 and 2, since the fiber structure 20 is schematically shown, detailed illustrations and hatching of the outer shapes of the first reinforcing fiber yarns 31 and the second reinforcing fiber yarns 21 are omitted. The fiber structure 20 is a unidirectional fabric. The fiber structure 20 is formed by arranging a plurality of first reinforcing fiber yarns 31 and a plurality of second reinforcing fiber yarns 21 so as to extend in the same direction. Therefore, the whole of the fiber structure 20 is a fiber arrangement portion formed by arranging the first reinforcing fiber yarns 31 and the second reinforcing fiber yarns 21 so as to extend in the same direction.

[0017] As shown in FIG. 3, the second reinforcing fiber yarn 21 is formed by bundling continuous fibers 22 made of reinforcing fibers. The continuous fibers 22 extend linearly and have straightness. The continuous fibers 22 are long fibers. Although the continuous fibers 22 are described as extending linearly and having straightness, in manufacturing, it is inevitable that they are slightly curved, so having straightness includes some curvature and twist.

[0018] Since the second reinforcing fiber yarn 21 is formed by bundling continuous fibers 22 extending linearly, in order to maintain the shape as a yarn, a slight twist is added to the fiber bundle of the continuous fibers 22. As the continuous fibers 22, organic fibers or inorganic fibers may be used, or different types of organic fibers, different types of inorganic fibers, or mixed fibers obtained by mixing organic fibers and inorganic fibers may also be used. Examples of organic fibers include acrylic fibers, nylon fibers, polyester fibers, aramid fibers, poly-p-phenylene benzobisoxazole fibers, ultra-high molecular weight polyethylene fibers, and the like. Examples of inorganic fibers include carbon fibers, glass fibers, ceramic fibers, and the like. In the present embodiment, the continuous fibers 22 are long carbon fibers as inorganic fibers.

[0019] As shown in FIG. 4, the first reinforcing fiber yarn 31 is formed by helically winding a covering yarn 33 around the outer peripheral portion of a fiber bundle including discontinuous fibers 32 made of reinforcing fibers. The covering yarn 33 holds the shape of the fiber bundle of the discontinuous fibers 32 in a yarn shape.

[0020] The discontinuous fibers 32 are short fibers. The discontinuous fibers 32 are formed by cutting long fibers. The discontinuous fibers 32 are shorter than the continuous fibers 22 of the second reinforcing fiber yarn 21. As the discontinuous fibers 32, organic fibers or inorganic fibers may be used, or different types of organic fibers, different types of inorganic fibers, or mixed fibers obtained by mixing organic fibers and inorganic fibers may also be used. Examples of organic fibers include acrylic fibers, nylon fibers, polyester fibers, aramid fibers, poly-p-phenylene benzobisoxazole fibers, ultra-high molecular weight polyethylene fibers, and the like. Examples of inorganic fibers include carbon fibers, glass fibers, ceramic fibers, and the like.

[0021] In this embodiment, the discontinuous fibers 32 are recycled carbon fibers used as regenerated fibers. The discontinuous fibers 32 are generated from the trim of multiaxial fabrics, the trim of the weaving edge of fabrics, cut continuous tows, etc. The discontinuous fibers 32 extend in a straight line and have straight-line properties. The discontinuous fibers 32 are untwisted. The cross-sectional shape of the first reinforcing fiber yarn 31 is maintained in a substantially circular shape by shape retention by the covering yarn 33. The first reinforcing fiber yarn 31 is formed with the fiber orientation of the discontinuous fibers 32 aligned in one direction.

[0022] The covering yarn 33 is made of organic fibers. When the fiber structure 20 is heated during the manufacturing of the fiber-reinforced composite material 10, the material of the covering yarn 33 is determined to be an organic fiber with a melting point such that the covering yarn 33 does not melt.

[0023] As shown in Figure 2, the axial direction of the fiber structure 20 coincides with the direction in which the first reinforcing fiber yarn 31 and the second reinforcing fiber yarn 21 extend. The axial direction of the fiber structure 20 is the direction in which the first reinforcing fiber yarn 31 and the second reinforcing fiber yarn 21 extend in a unidirectional fabric. The direction in which the first reinforcing fiber yarn 31 and the second reinforcing fiber yarn 21 extend is the axial direction L of the fiber structure 20. Therefore, each of the continuous fibers 22 of the second reinforcing fiber yarn 21 and the discontinuous fibers 32 of the first reinforcing fiber yarn 31 extends linearly in the axial direction L of the fiber structure 20 and has straight-line properties. In the fiber structure 20, the cross-section where the axial direction L is perpendicular is quadrilateral. In the quadrilateral cross-section of the fiber structure 20, the direction in which two opposing sides extend is called the first direction X, and the direction in which the other two opposing sides extend is called the second direction Y. The first direction X and the second direction Y are perpendicular. Furthermore, the direction perpendicular to the first direction X and the second direction Y is the axial direction L.

[0024] The ratio of the first reinforcing fiber yarn 31 to the second reinforcing fiber yarn 21 per unit area of ​​the fiber structure 20 is arbitrary. In a fiber structure 20 using the fiber structure 20 as a reinforcing base material, if it is desired to increase the strength in the axial direction L, the ratio of the first reinforcing fiber yarn 31 to the second reinforcing fiber yarn 21 per unit area should be such that the ratio of the first reinforcing fiber yarn 31 is greater than that of the second reinforcing fiber yarn 21. Furthermore, since the discontinuous fibers 32 in the first reinforcing fiber yarn 31 are recycled carbon fibers, from the viewpoint of utilizing recycled carbon fibers, it is preferable that the ratio of the first reinforcing fiber yarn 31 to the second reinforcing fiber yarn 21 per unit area is such that the ratio of the first reinforcing fiber yarn 31 is greater than that of the second reinforcing fiber yarn 21.

[0025] In the fiber structure 20, the first reinforcing fiber yarn 31 and the second reinforcing fiber yarn 21 are randomly arranged in the first direction X and the second direction Y. Alternatively, the first reinforcing fiber yarn 31 and the second reinforcing fiber yarn 21 may be arranged alternately in the first direction X and the second direction Y to be aligned. In the fiber structure 20, the second reinforcing fiber yarn 21 is adjacent to the first reinforcing fiber yarn 31 not only in the first direction X and the second direction Y, but also in other directions. The fiber structure 20 includes a portion in which one second reinforcing fiber yarn 21 is sandwiched by two first reinforcing fiber yarns 31 from the first direction X, a portion in which one second reinforcing fiber yarn 21 is sandwiched by two first reinforcing fiber yarns 31 from the second direction Y, and a portion in which one second reinforcing fiber yarn 21 is sandwiched by two first reinforcing fiber yarns 31 from directions other than the first direction X and the second direction Y. In the fiber structure 20, the second reinforcing fiber yarn 21 is sandwiched by the first reinforcing fiber yarn 31 from various directions. In other words, the second reinforcing fiber yarn 21 is positioned between the first reinforcing fiber yarns 31. Therefore, the fiber structure 20 as a fiber arrangement section has many portions in which the second reinforcing fiber yarn 21 is sandwiched by the first reinforcing fiber yarn 31. The fiber structure 20 is a reinforcing base material of a prepreg impregnated with matrix resin 12. Therefore, the fiber-reinforced composite material 10 is a prepreg.

[0026] <Method for manufacturing fiber structures> As shown in Figure 5, the fiber-reinforced composite material 10 is manufactured by a pultrusion molding apparatus 40. The fiber structure 20 is then manufactured during the manufacturing process of the fiber-reinforced composite material 10.

[0027] The pultrusion molding apparatus 40 comprises a supply unit 41, an impregnation layer 42, a compression unit 43, a heating mold 44, a pultrusion unit 45, and a cutting unit 46. The supply unit 41 includes a supply unit 41a for the second reinforcing fiber yarn 21 and a supply unit 41b for the first reinforcing fiber yarn 31. The supply unit 41 feeds the first reinforcing fiber yarn 31 and the second reinforcing fiber yarn 21 in one direction for manufacturing the fiber structure 20. The first reinforcing fiber yarn 31 and the second reinforcing fiber yarn 21 are pulled by the pultrusion unit 45. As the first reinforcing fiber yarn 31 and the second reinforcing fiber yarn 21 are pulled by the pultrusion unit 45, they are fed out of the supply unit 41.

[0028] When the first reinforcing fiber yarn 31 and the second reinforcing fiber yarn 21 are fed from the supply unit 41, they are fed out in a state where they are randomly arranged in the first direction X and the second direction Y. Alternatively, when the first reinforcing fiber yarn 31 and the second reinforcing fiber yarn 21 are fed out from the supply unit 41, they may be fed out in a state where they are aligned alternately in the first direction X and the second direction Y. However, even if the first reinforcing fiber yarn 31 and the second reinforcing fiber yarn 21 are fed out in an alternate state in the first direction X and the second direction Y, they will mix together in a random state on their way to the impregnation layer 42.

[0029] The first reinforcing fiber yarn 31 and the second reinforcing fiber yarn 21, which are fed out from the supply unit 41, are bundled together. In other words, the first reinforcing fiber yarn 31 and the second reinforcing fiber yarn 21 are fed out by the supply unit 41 in an order that they extend in the same direction, thereby forming a fiber arrangement and a fiber structure 20. In the following description, the fiber arrangement consisting of the first reinforcing fiber yarn 31 and the second reinforcing fiber yarn 21 fed out from the supply unit 41 will be referred to as the fiber structure 20. Note that Figure 5 schematically shows the pultrusion molding apparatus 40, and therefore the fiber structure 20 is also shown schematically.

[0030] As shown in Figure 2, gaps are formed between adjacent first reinforcing fiber threads 31 in the fiber structure 20 in the first direction X, the second direction Y, and other directions. Gaps are also formed between adjacent second reinforcing fiber threads 21 in the first direction X, the second direction Y, and other directions. Furthermore, gaps are formed between adjacent second reinforcing fiber threads 21 and first reinforcing fiber threads 31 in the first direction X, the second direction Y, and other directions.

[0031] As shown in Figure 5, the impregnation layer 42 contains a matrix resin 12 in a liquid state. The matrix resin 12 contained in the impregnation layer 42 is a high-temperature molten resin. In the impregnation layer 42, the matrix resin 12 impregnates the fiber structure 20 that is fed out from the supply unit 41. The fiber structure 20 passes through the impregnation layer 42 continuously in the direction in which the first reinforcing fiber yarn 31 and the second reinforcing fiber yarn 21 extend.

[0032] The matrix resin 12 impregnates each first reinforcing fiber yarn 31 and each second reinforcing fiber yarn 21 of the fiber structure 20, and the matrix resin 12 impregnates the entire fiber structure 20. In the fiber structure 20, the matrix resin 12 fills the spaces between adjacent second reinforcing fiber yarns 21, between adjacent first reinforcing fiber yarns 31, and between adjacent first reinforcing fiber yarns 31 and second reinforcing fiber yarns 21. In addition, the entire surface of the fiber structure 20 is covered with the matrix resin 12. In other words, the matrix resin 12 fills the gaps that existed in the fiber structure 20.

[0033] As shown in Figure 5, the compression unit 43 compresses the fiber structure 20 impregnated with the matrix resin 12. The compression of the fiber structure 20 by the compression unit 43 pressurizes the entire fiber structure 20 in the second direction Y, and the first reinforcing fiber yarn 31 and the second reinforcing fiber yarn 21 are also pressurized in the second direction Y. The compression of the fiber structure 20 by the compression unit 43 removes excess matrix resin 12 from the fiber structure 20.

[0034] Then, when the fiber structure 20 is pressurized, the second reinforcing fiber yarn 21 is released from its bundled state due to the pressurization. The second reinforcing fiber yarn 21 deforms under the pressurization so that the spacing between the continuous fibers 22 widens. As a result, the continuous fibers 22 that make up the second reinforcing fiber yarn 21 separate.

[0035] As a result, as shown in Figure 1, the continuous fibers 22 are dispersed in the matrix resin 12 that was interwoven between adjacent first reinforcing fiber threads 31. This produces a fiber-reinforced composite material 10.

[0036] As shown in Figure 5, the heating mold 44 heats the fiber structure 20, i.e., the fiber-reinforced composite material 10, which is impregnated with the matrix resin 12. The pulling section 45 pulls the heated fiber-reinforced composite material 10 of the matrix resin 12 in the heating mold 44. The cutting section 46 cuts the thermo-cured fiber-reinforced composite material 10 of the matrix resin 12 to the desired length.

[0037] <Operation of the First Embodiment> As shown in Figure 1, in the fiber-reinforced composite material 10, the shape of each first reinforcing fiber yarn 31 is slightly flattened by the pressure applied by compression, but the state in which the discontinuous fibers 32 are bundled by the covering yarn 33 is maintained. The discontinuous fibers 32 of each first reinforcing fiber yarn 31 are slightly disrupted by the pressure applied by compression, but they remain almost straight. Therefore, the strength provided by the first reinforcing fiber yarns 31 is ensured in the fiber-reinforced composite material 10.

[0038] Each second reinforcing fiber yarn 21 is not held together by the covering yarn 33 like the first reinforcing fiber yarn 31. Therefore, the shape of each second reinforcing fiber yarn 21 changes significantly due to the pressure applied by compression. The continuous fibers 22 of each second reinforcing fiber yarn 21 move randomly to widen the spacing between the continuous fibers 22 under the pressure applied by compression. Therefore, each second reinforcing fiber yarn 21 is more scattered than before the pressure applied by compression. In the fiber-reinforced composite material 10, the first reinforcing fiber yarn 31 is adjacent not only in the first direction X and the second direction Y, but also in directions perpendicular to both the first direction X and the second direction Y, and in various other directions. The continuous fibers 22 of the second reinforcing fiber yarn 21 are dispersed in the various directions mentioned above and dispersed among adjacent first reinforcing fiber yarns 31.

[0039] The matrix resin 12 is embedded between adjacent first reinforcing fiber yarns 31. As described above, the continuous fibers 22 of the second reinforcing fiber yarn 21 are dispersed between adjacent first reinforcing fiber yarns 31 in all directions. Therefore, the continuous fibers 22 of the second reinforcing fiber yarn 21 are dispersed in the matrix resin 12 embedded between the first reinforcing fiber yarns 31. In other words, the occurrence of resin-rich areas consisting only of matrix resin 12 is suppressed.

[0040] The dispersed continuous fibers 22 extend in an almost straight line. Therefore, the strength provided by the continuous fibers 22 is ensured in the fiber-reinforced composite material 10. According to the first embodiment described above, the following effects can be obtained.

[0041] (1-1) During the manufacture of the fiber-reinforced composite material 10, the fiber structure 20 impregnated with matrix resin 12 is pressurized by the compression section 43. At this time, continuous fibers 22 are dispersed between the first reinforcing fiber threads 31. Therefore, in the fiber-reinforced composite material 10 using the fiber structure 20 as the reinforcing base material, continuous fibers 22 are dispersed in the matrix resin 12 filled between the first reinforcing fiber threads 31. Consequently, in the fiber-reinforced composite material 10 using the fiber structure 20 as the reinforcing base material, the occurrence of resin richness between the first reinforcing fiber threads 31 can be suppressed.

[0042] (1-2) In the fiber-reinforced composite material 10, the first reinforcing fiber yarn 31 is formed using untwisted discontinuous fibers 32 in order to align the fiber orientation and ensure the strength of the fiber-reinforced composite material 10. The discontinuous fibers 32 are recycled carbon fibers obtained from the trim of multiaxial fabrics, the trim of the weaving edge of fabrics, shredded continuous tow, etc. In order to reuse these recycled carbon fibers as yarn, it is necessary to bundle the discontinuous fibers 32. Therefore, the first reinforcing fiber yarn 31 made from recycled discontinuous fibers 32 requires a covering yarn 33. For this reason, the shape change of the first reinforcing fiber yarn 31 due to pressure is minimal. Even in a fiber structure 20 using such first reinforcing fiber yarn 31, the occurrence of resin richness between the first reinforcing fiber yarns 31 can be suppressed by utilizing the ease with which the second reinforcing fiber yarn 21 can unravel.

[0043] (1-3) The fiber structure 20 is a unidirectional woven fabric. During the manufacture of the fiber-reinforced composite material 10, the arrangement of the first reinforcing fiber yarns 31 and the second reinforcing fiber yarns 21 is easily disrupted by the pressure applied to the fiber structure 20 by the compression section 43. For this reason, in a unidirectional woven fiber structure 20, the second reinforcing fiber yarns 21 are easily positioned between the first reinforcing fiber yarns 31. As a result, the continuous fibers 22 are easily dispersed between the first reinforcing fiber yarns 31 by the pressure applied to the fiber structure 20. Therefore, a unidirectional woven fiber structure 20 is more likely to suppress the occurrence of resin richness between the first reinforcing fiber yarns 31.

[0044] (Second embodiment) Next, a second embodiment of the fiber structure and fiber-reinforced composite material will be described with reference to Figures 6 and 7. Note that detailed explanations of parts of the second embodiment that are the same as those of the first embodiment will be omitted.

[0045] As shown in Figure 6, the fiber structure 60 of the fiber-reinforced composite material 50 is a woven fabric comprising a warp layer 65 made of warp threads 61 and a weft layer 66 made of weft threads 62. The fiber structure 60 is formed by joining two stacked fabrics in the stacking direction with binding threads 64. Each of the two fabrics comprises one warp layer 65 and two weft layers 66. One warp layer 65 is sandwiched between the two weft layers 66.

[0046] The warp layer 65 is formed by arranging multiple warp threads 61 so that they extend in the same direction. The weft layer 66 is formed by arranging multiple weft threads 62 so that they extend in the same direction. The directions in which the warp threads 61 extend and the directions in which the weft threads 62 extend intersect.

[0047] The warp threads 61 include a first reinforcing fiber yarn 31 and a second reinforcing fiber yarn 21. In the warp layer 65, there are areas where the first reinforcing fiber yarn 31 and the second reinforcing fiber yarn 21 are arranged so that two second reinforcing fiber yarns 21 are sandwiched between the first reinforcing fiber yarns 31, and areas where the first reinforcing fiber yarn 31 and the second reinforcing fiber yarn 21 are arranged so that one second reinforcing fiber yarn 21 is sandwiched between the first reinforcing fiber yarns 31. The arrangement of the second reinforcing fiber yarns 21 and the first reinforcing fiber yarns 31 in the warp layer 65 can be changed as appropriate. For example, the first reinforcing fiber yarns 31 and the second reinforcing fiber yarns 21 may be arranged alternately. In the fiber structure 60, the warp layer 65 is a fiber arrangement section comprising the first reinforcing fiber yarn 31 and the second reinforcing fiber yarn 21 as warp threads 61. Therefore, the fiber structure 60 comprises a fiber arrangement section.

[0048] The weft layer 66 is formed solely of the first reinforcing fiber yarn 31. The weft layer 66 is formed by arranging multiple weft yarns 62 so that they extend in the same direction. Any yarn can be used for the binding yarn 64. The binding yarn 64 extends in the lamination direction of the warp layer 65 and the weft layer 66, and is folded back in the outermost weft layer 66 of the fiber structure 60.

[0049] In the warp layer 65, where the binding threads 64 extend in the lamination direction, the warp threads 61 are slightly separated by the binding threads 64. In the warp layer 65, the second reinforcing fiber threads 21 are adjacent to the binding threads 64 that extend in the lamination direction. In other words, the second reinforcing fiber threads 21 are separated by the binding threads 64.

[0050] The fiber-reinforced composite material 50 is formed by the RTM (Resin Transfer Molding) method. As shown in Figure 7, the fiber-reinforced composite material 50 is manufactured by filling a mold 70 in which the fiber structure 60 is placed with matrix resin 12. Once the matrix resin 12 is filled into the mold 70, the fiber structure 60 is pressurized by the filling pressure of the matrix resin 12. The matrix resin 12 filled into the mold 70 also impregnates the fiber structure 60.

[0051] In the warp layer 65 and weft layer 66 of the fiber structure 60, the matrix resin 12 impregnates each first reinforcing fiber yarn 31 and each second reinforcing fiber yarn 21, and the matrix resin 12 impregnates the entire fiber structure 60. In the warp layer 65, the matrix resin 12 fills the spaces between adjacent second reinforcing fiber yarns 21 and between adjacent second reinforcing fiber yarns 21 and first reinforcing fiber yarns 31. In the weft layer 66, the matrix resin 12 fills the spaces between adjacent weft yarns 62. When the matrix resin 12 and the fiber structure 60 are heated in the mold 70, the matrix resin 12 hardens and the matrix resin 12 is compounded. As a result, a fiber-reinforced composite material 50 is manufactured, with the matrix resin 12 as the base material and the fiber structure 60 as the reinforcing base material.

[0052] <Operation of the second embodiment> In the fiber-reinforced composite material 50, in the warp layer 65 of the fiber structure 60, the shape of each first reinforcing fiber 31 is slightly flattened by the filling pressure of the matrix resin 12, but the state in which the discontinuous fibers 32 are bundled by the covering yarn 33 is maintained. The discontinuous fibers 32 of each first reinforcing fiber 31 are slightly disrupted by the filling pressure, but they remain almost straight. Therefore, the strength provided by the first reinforcing fiber 31 is ensured in the fiber-reinforced composite material 50.

[0053] In the warp layer 65, each second reinforcing fiber 21 is not held together by the covering yarn 33 like the first reinforcing fiber 31. Therefore, the shape of each second reinforcing fiber 21 changes significantly due to the filling pressure. The continuous fibers 22 of each second reinforcing fiber 21 move randomly in response to the filling pressure, widening the spacing between the continuous fibers 22. As a result, each second reinforcing fiber 21 is more scattered than before the matrix resin 12 was filled. Furthermore, the continuous fibers 22 of the second reinforcing fiber 21 are dispersed among adjacent first reinforcing fiber 31 in the warp layer 65.

[0054] The matrix resin 12 is embedded between adjacent first reinforcing fibers 31 in the warp layer 65. As described above, the continuous fibers 22 of the second reinforcing fibers 21 are dispersed between adjacent first reinforcing fibers 31. Therefore, the continuous fibers 22 of the second reinforcing fibers 21 are dispersed in the matrix resin 12 embedded between the first reinforcing fibers 31. In other words, the occurrence of resin-rich areas consisting solely of matrix resin 12 is suppressed in the warp layer 65.

[0055] According to the second embodiment described above, the following effects can be obtained. (2-1) During the production of the fiber-reinforced composite material 50 by the RTM method, the fiber structure 60 impregnated with matrix resin 12 is pressurized by the filling pressure of the matrix resin 12. At this time, in the warp layer 65, continuous fibers 22 are dispersed between the first reinforcing fiber yarns 31. Therefore, in the fiber-reinforced composite material 50 using the fiber structure 60 as the reinforcing base material, continuous fibers 22 are dispersed in the matrix resin 12 filled between the first reinforcing fiber yarns 31. Consequently, the occurrence of resin richness between the first reinforcing fiber yarns 31 can be suppressed in the fiber-reinforced composite material 50.

[0056] (2-2) The fiber structure 60 is a woven fabric comprising a warp layer 65 and a weft layer 66. The warp layer 65 comprises a first reinforcing fiber yarn 31 and a second reinforcing fiber yarn 21. Therefore, the occurrence of resin richness between the first reinforcing fiber yarns 31 in the warp layer 65 is suppressed. Thus, in the fiber-reinforced composite material 50 using a woven fabric made of warp yarns 61 and weft yarns 62 as the reinforcing base material, the reduction in strength due to areas filled only with matrix resin 12 can be suppressed.

[0057] Furthermore, each of the above embodiments can be implemented with the following modifications. The above embodiments and the following modifications can be combined with each other to the extent that they do not contradict each other technically. ○In the fiber structure 60 of the second embodiment, not only the warp layer 65 but also the weft layer 66 may be a fiber arrangement portion formed by the first reinforcing fiber yarn 31 and the second reinforcing fiber yarn 21.

[0058] ○In the fiber structure 60 of the second embodiment, the weft layer 66 may be a fiber arrangement portion formed of a first reinforcing fiber yarn 31 and a second reinforcing fiber yarn 21, while the warp layer 65 may be formed of only the first reinforcing fiber yarn 31.

[0059] ○In the first reinforcing fiber yarn 31, the bundle of discontinuous fibers 32 may be twisted. In this case, the twisting of the bundle of discontinuous fibers 32 and the covering yarn 33 can further suppress the unraveling of the first reinforcing fiber yarn 31.

[0060] ○In the first embodiment, the fiber-reinforced composite material 10 may be formed by laminating multiple unidirectional prepreg sheet materials, each of which is made by impregnating a matrix resin 12 into a unidirectional woven fabric in which a plurality of first reinforcing fiber yarns 31 and a plurality of second reinforcing fiber yarns 21 are arranged in one direction.

[0061] ○The covering yarn 33 of the first reinforcing fiber yarn 31 may be a reinforcing fiber other than an organic fiber. The material of the covering yarn 33 may be, for example, carbon fiber, aramid fiber, or glass fiber.

[0062] ○The first reinforcing fiber yarn 31 may include discontinuous fibers 32 and may be formed by wrapping a covering yarn 33 around a fiber bundle that includes continuous fibers. ○The discontinuous fibers 32 of the first reinforcing fiber yarn 31 do not have to be recycled carbon fibers; unused carbon fibers or new carbon fibers may also be used.

[0063] ○In the second embodiment, the type of fabric in the fiber structure 60 may be changed as appropriate. [Explanation of Symbols]

[0064] 10, 50…Fiber-reinforced composite material, 12…Matrix resin, 20…Fiber structure as fiber arrangement area, 21…Second reinforcing fiber yarn, 22…Continuous fiber, 31…First reinforcing fiber yarn, 32…Discontinuous fiber, 33…Covering yarn, 60…Fiber structure, 61…Warp yarn, 62…Weft yarn, 65…Warp layer as fiber arrangement area, 66…Weft layer.

Claims

1. A fibrous structure that serves as a reinforcing base material for a fiber-reinforced composite material with a matrix resin as the base material, A first reinforcing fiber yarn in which a covering yarn is wrapped around the outer circumference of a fiber bundle containing discontinuous fibers made of reinforcing fiber, It comprises a second reinforcing fiber yarn formed by bundling continuous fibers made of reinforcing fibers, A fiber structure comprising a fiber arrangement portion formed by arranging the first reinforcing fiber yarn and the second reinforcing fiber yarn so as to extend in the same direction, wherein the fiber arrangement portion comprises a portion in which the second reinforcing fiber yarn is sandwiched by the first reinforcing fiber yarn.

2. The fiber structure according to claim 1, wherein the fiber structure is a unidirectional woven fabric in which the entire fiber structure is the fiber arrangement portion.

3. The fiber structure is a woven fabric comprising a warp layer made of warp threads and a weft layer made of weft threads, wherein the fiber arrangement portion is the warp layer, and the warp layer comprises the first reinforcing fiber yarn and the second reinforcing fiber yarn as the warp threads, as described in claim 1.

4. A fiber-reinforced composite material having a matrix resin as the base material and a fiber structure as the reinforcing base material, The aforementioned fiber structure is A first reinforcing fiber yarn in which a covering yarn is wrapped around the outer circumference of a fiber bundle containing discontinuous fibers made of reinforcing fiber, It comprises a second reinforcing fiber yarn formed by bundling continuous fibers made of reinforcing fibers, The fiber arrangement portion is formed by arranging the first reinforcing fiber yarn and the second reinforcing fiber yarn so that they extend in the same direction, and the fiber arrangement portion includes a portion in which the second reinforcing fiber yarn is sandwiched by the first reinforcing fiber yarn. A fiber-reinforced composite material characterized in that the continuous fibers are dispersed in the matrix resin filled between the first reinforcing fiber threads.

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