Fiber structure

Abstract

To provide a fiber-reinforced composite material formed of a fiber structure, which improves strength while suppressing lowering of pressure-resistant strength and fatigue characteristics and increase in a weight.SOLUTION: A fiber layer 51 is composed of a first fiber layer 61 having a first thread and a second thread which is different from the first thread and extends in a thread main axis direction, and a second fiber layer 62 having the first thread and the second thread. The first thread and the second thread are composed of a reinforcement fiber. The first fiber layer 61 does not have an entangled part where the second thread is entangled with the first thread. The fiber layer 51 constituting an inner surface 20a of a cylindrical body 20 is defined as an innermost layer 51a, and the fiber layer 51 constituting an outer surface 20b of the cylindrical body 20 is defined as an outermost layer 51b. The second fiber layer 62 constitutes the outermost layer 51b, and has an entangled part.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a fiber structure.

Background Art

[0002] As a fiber structure, for example, a fiber-reinforced composite material is formed by impregnating a thermosetting resin using the RTM (Resin Transfer Molding) method. The fiber structure includes, for example, a cylindrical tubular body. The tubular body includes, for example, a plurality of fiber layers laminated on each other in the lamination direction. The plurality of fiber layers include, for example, a first yarn and a second yarn extending in a yarn spindle direction different from that of the first yarn.

[0003] The fiber structure described in Patent Document 1 has a so-called crimp-less structure in which the second yarn does not entangle with the first yarn. The first yarn and the second yarn are made of reinforcing fibers. The less the entanglement portion of the second yarn that entangles with the first yarn, the less the meandering of the second yarn with respect to the first yarn. Therefore, the less the entanglement portion of the fiber structure, the higher the strength of the fiber-reinforced composite material formed from the fiber structure.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When resin impregnation is performed on a fiber structure with few entanglement portions using the RTM method, the reinforcing fibers located in the outermost layer of the fiber structure may meander due to the impregnation resistance of the resin. As a result, in the fiber-reinforced composite material formed from the fiber structure, the pressure resistance and fatigue characteristics may decrease.

Means for Solving the Problems

[0006] The fiber structure for solving the above problems is a fiber structure for forming a fiber-reinforced composite material by impregnating a thermosetting resin using the RTM method. The fiber structure includes a cylindrical tube body. The tube body includes a plurality of fiber layers laminated on each other in the lamination direction. The plurality of fiber layers include a first fiber layer including at least one of a first yarn and a second yarn extending in a yarn spindle direction different from that of the first yarn, and a second fiber layer including the first yarn and the second yarn. The first yarn and the second yarn are made of reinforcing fibers. The first fiber layer does not include an entanglement portion where the second yarn is entangled with the first yarn. When the fiber layer constituting the inner surface of the tube body is defined as the innermost layer and the fiber layer constituting the outer surface of the tube body is defined as the outermost layer, the second fiber layer constitutes at least one of the innermost layer and the outermost layer and includes the entanglement portion.

[0007] The fiber structure for solving the above problems is a fiber structure for forming a fiber-reinforced composite material by impregnating a thermosetting resin using the RTM method. The fiber structure includes a cylindrical tube body. The tube body includes a plurality of fiber layers laminated on each other in the lamination direction. The plurality of fiber layers include a first fiber layer including at least one of a first yarn and a second yarn extending in a yarn spindle direction different from that of the first yarn, and a second fiber layer including the first yarn and the second yarn. The first yarn and the second yarn are made of reinforcing fibers. The first fiber layer and the second fiber layer include an entanglement portion where the second yarn is entangled with the first yarn. At least one of the first fiber layer and the second fiber layer is made of a fabric. When the fiber layer constituting the inner surface of the tube body is defined as the innermost layer and the fiber layer constituting the outer surface of the tube body is defined as the outermost layer, the second fiber layer constitutes at least one of the innermost layer and the outermost layer and includes more of the entanglement portion than the first fiber layer.

[0008] When impregnating a thermosetting resin using the RTM method, the fiber layer located in the innermost layer or the outermost layer is subject to the impregnation resistance of the thermosetting resin. According to each of the above configurations, at least one of the innermost layer and the outermost layer is constituted by a second fiber layer. The second fiber layer has more entanglement portions where the second yarn is entangled with the first yarn than the first fiber layer. Therefore, in the second fiber layer, meandering of the reinforcing fibers due to the impregnation resistance of the thermosetting resin hardly occurs. Accordingly, in the fiber-reinforced composite material formed from the fiber structure, a decrease in pressure resistance and fatigue characteristics can be suppressed.

[0009] According to each of the above configurations, the entanglement portion provided in the first fiber layer is less than that in the second fiber layer. Therefore, compared with the second fiber layer, the first fiber layer has less meandering of the second yarn due to the entanglement of the second yarn with the first yarn. By providing a plurality of fiber layers with the first fiber layer, the strength of the fiber-reinforced composite material formed using the fiber structure can be improved. Since the strength of the fiber-reinforced composite material can be improved without increasing the total number or thickness of the first yarns and the second yarns constituting the fiber structure, an increase in the weight of the fiber-reinforced composite material can be suppressed. Accordingly, in the fiber-reinforced composite material formed from the fiber structure, it is possible to improve the strength while suppressing a decrease in pressure resistance and fatigue characteristics and an increase in weight.

[0010] In the fiber structure, the first fiber layer may include the first yarn, and the first yarn may be continuous between the first fiber layer and the second fiber layer. According to the above configuration, the strength of the fiber structure in the yarn spindle direction of the first yarn can be improved as compared with the case where the first yarn constituting the first fiber layer and the first yarn constituting the second fiber layer are not continuous with each other. Accordingly, the strength of the fiber-reinforced composite material formed from the fiber structure can be further improved.

Advantages of the Invention

[0011] According to this invention, in the fiber-reinforced composite material formed from the fiber structure, it is possible to improve the strength while suppressing a decrease in pressure resistance and fatigue characteristics and an increase in weight.

Brief Description of the Drawings

[0012]

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MODE FOR CARRYING OUT THE INVENTION

[0013] (First Embodiment) Next, a first embodiment in which the fiber structure is embodied will be described with reference to FIGS. 1 to 11. Hereinafter, a fiber structure applied to a pressure vessel will be exemplified. For convenience of explanation, the fiber structure will be described after the description of the pressure vessel. In the drawings, the X-axis, the Y-axis, and the Z-axis are illustrated as axes orthogonal to each other. Hereinafter, the direction parallel to the X-axis is referred to as the axial direction X.

[0014] [Basic Structure of Pressure Vessel] As shown in FIG. 1, the pressure vessel 10 includes a fiber-reinforced composite material 11 and a liner 12. The pressure vessel 10 of the present embodiment is a high-pressure tank for storing hydrogen gas inside. The liner 12 is made of, for example, resin. The fiber-reinforced composite material 11 includes a fiber structure 19. The fiber structure 19 is impregnated with a thermosetting resin as a matrix resin Ma. By impregnating the fiber structure 19 with a thermosetting resin using the RTM method, the fiber-reinforced composite material 11 is formed. Examples of the thermosetting resin include epoxy resin, vinyl ester resin, unsaturated polyester resin, and phenolic resin. The liner 12 is reinforced by the fiber-reinforced composite material 11, thereby ensuring the pressure resistance of the pressure vessel 10.

[0015] [Basic Structure of Precursor of Pressure Vessel] Next, the structure of the precursor 10a of the pressure vessel 10 will be described. As shown in FIG. 2, the precursor 10a is composed of a fiber structure 19 and a liner 12. The fiber structure 19 in the precursor 10a is a fiber preform 19a for the pressure vessel 10 for manufacturing the pressure vessel 10 by impregnating a thermosetting resin.

[0016] The precursor 10a is different from the pressure vessel 10 in that it does not include the fiber-reinforced composite material 11. Except for this point, the precursor 10a has the same configuration as the pressure vessel 10. Hereinafter, the configuration of the precursor 10a will be described with reference to FIGS. 2 to 8, but unless otherwise specified, the following description is also common to the pressure vessel 10.

[0017] [Structure of Liner] As shown in FIG. 3, the liner 12 includes a cylindrical body portion 13 and a dome portion 14. The body portion 13 of the present embodiment is cylindrical. The central axis of the body portion 13 extends in the axial direction X. The central axis of the body portion 13 is simply referred to as the central axis L. The central axis L coincides with the central axis of the liner 12. The dome portion 14 is located at the end of the body portion 13 in the axial direction X and the end in the direction opposite to the axial direction X. The dome portion 14 has a shape that tapers toward the tip of the dome portion 14. The internal space of the liner 12 is partitioned and formed by the body portion 13 and the dome portion 14.

[0018] The fiber structure 19 covers the liner outer surface 12a which is the outer surface of the liner 12. The liner outer surface 12a is composed of a body outer surface 13a which is the outer surface of the body portion 13 and a dome outer surface 14a which is the outer surface of the dome portion 14.

[0019] The liner 12 includes base portions 15 at the end in the axial direction X and the end in the direction opposite to the axial direction X. The base portion 15 is made of, for example, metal. The base portion 15 includes a connection portion 15a that connects to the dome portion 14 and a protruding portion 15b that protrudes from the connection portion 15a.

[0020] The connection portion 15a is located at the tip of the dome portion 14. The protruding portion 15b penetrates the fiber structure 19. A base hole 15c is formed inside the connection portion 15a and the protruding portion 15b. The base hole 15c penetrates the connection portion 15a and the protruding portion 15b in the axial direction X. The internal space of the liner 12 and the outside of the liner 12 communicate with each other through the base hole 15c.

[0021] Although not shown, when a valve is attached to one of the base portions 15, the base hole 15c of one of the base portions 15 is closed. When a screw is screwed into the other base portion 15, the base hole 15c of the other base portion 15 is closed.

[0022] [Structure of Fiber Structure] As shown in FIGS. 2 and 3, the fiber structure 19 includes a cylindrical tubular body 20. The central axis of the tubular body 20 extends in the axial direction X. The central axis of the tubular body 20 coincides with the central axis L. The tubular body 20 includes a plurality of fiber layers 51. The plurality of fiber layers 51 are laminated on each other in the lamination direction LD. The fiber layer 51 of the present embodiment covers the outer surface 13a of the body. The fiber structure 19 of the present embodiment includes a dome fiber layer 52. The dome fiber layer 52 covers the outer surface 14a of each of the dome portions 14.

[0023] [Structure of fiber layer] As shown in FIG. 4, the plurality of fiber layers 51 are laminated in the lamination direction LD with respect to the outer surface 13a of the body. The lamination direction LD is a direction orthogonal to the outer surface 12a of the liner. In the present embodiment, the plurality of fiber layers 51 are composed of a first fiber layer 61 and a second fiber layer 62. The first fiber layer 61 of the present embodiment is laminated a plurality of times in the lamination direction LD with respect to the outer surface 13a of the body.

[0024] The fiber layer 51 that constitutes the inner surface 20a of the tubular body 20 is defined as the innermost layer 51a. The fiber layer 51 that constitutes the outer surface 20b of the tubular body 20 is defined as the outermost layer 51b. The innermost layer 51a is the fiber layer 51 that is closest to the body portion 13 in the lamination direction LD. The outermost layer 51b is the fiber layer 51 that is farthest from the body portion 13 in the lamination direction LD. The second fiber layer 62 of the present embodiment constitutes the outermost layer 51b. The first fiber layer 61 of the present embodiment constitutes a plurality of fiber layers 51 other than the outermost layer 51b. That is, the innermost layer 51a of the present embodiment is constituted by the first fiber layer 61.

[0025] The first fiber layer 61 and the second fiber layer 62 may be bonded in the lamination direction LD by an interlayer bonding thread (not shown). Also, a plurality of first fiber layers 61 may be bonded to each other by an interlayer bonding thread (not shown). In this case, for example, two layers of the first fiber layer 61 that overlap in the lamination direction LD are bonded to each other by an interlayer bonding thread. Thereby, in the plurality of fiber layers 51, a plurality of sets of the first fiber layer 61 bonded by the interlayer bonding thread may be located.

[0026] [Structure of the first fiber layer] As shown in FIGS. 5 and 6, the first fiber layer 61 of the present embodiment includes a first yarn 31 and a second yarn 32. The first yarn 31 and the second yarn 32 are made of reinforcing fibers. Examples of the reinforcing fibers include carbon fibers and glass fibers. The first fiber layer 61 includes a plurality of the first yarns 31 and a plurality of the second yarns 32. Both the first yarn 31 and the second yarn 32 have a flat cross-sectional shape. The finenesses of the first yarn 31 and the second yarn 32 are of the same numerical value. When looking at the cross-sectional shapes of the first yarn 31 and the second yarn 32, the diameter of the first yarn 31 and the diameter of the second yarn 32 are of the same size.

[0027] As shown in FIG. 3, the yarn main axis direction of the first yarn 31 is referred to as a first yarn main axis direction W1. The first yarn main axis direction W1 coincides with the circumferential direction centered on the central axis L. The yarn main axis direction of the second yarn 32 arranged on the outer surface 13a of the body is referred to as a second yarn main axis direction W2. The second yarn main axis direction W2 coincides with the axial direction X. That is, the second yarn 32 extends in a yarn main axis direction different from that of the first yarn 31.

[0028] As shown in FIGS. 6 and 7, each of the first fiber layers 61 includes a first yarn layer 61a and a second yarn layer 61b. The first yarn layer 61a is composed of a plurality of first yarns 31 arranged in the axial direction X. The plurality of first yarns 31 in the first yarn layer 61a are parallel to each other. The second yarn layer 61b is composed of a plurality of second yarns 32 arranged in the circumferential direction of the liner 12. The plurality of second yarns 32 in the second yarn layer 61b are parallel to each other. Each of the first yarn layer 61a and the second yarn layer 61b is a so-called UD (Uni Directional) sheet composed of yarns in a single direction.

[0029] Each first yarn layer 61a of the first fiber layer 61 is laminated on the second yarn layer 61b in the lamination direction LD. When looking at the first fiber layer 61 from the lamination direction LD, the plurality of first yarns 31 constituting the first yarn layer 61a and the plurality of second yarns 32 constituting the second yarn layer 61b are orthogonal to each other. By laminating a plurality of first fiber layers 61 in the lamination direction LD, the first yarn layer 61a and the second yarn layer 61b are alternately laminated in the lamination direction LD.

[0030] The first yarn 31 of the first yarn layer 61a constitutes the first yarn 31 of the first fiber layer 61. The second yarn 32 of the second yarn layer 61b constitutes the second yarn 32 of the first fiber layer 61. The first fiber layer 61 of the present embodiment has a so-called crimp press structure in which the second yarn 32 is not entangled with the first yarn 31. The first fiber layer 61 does not include an entanglement portion 63 where the second yarn 32 is entangled with the first yarn 31.

[0031] [Structure of the second fiber layer] As shown in FIGS. 5 and 6, the second fiber layer 62 includes the first yarn 31 and the second yarn 32. The second fiber layer 62 is a fabric 60 in which the second yarn 32 is entangled with the first yarn 31. The second fiber layer 62 of the present embodiment is a single-layer fabric formed by plain weaving.

[0032] As shown in FIGS. 6 and 8, the second fiber layer 62 is composed of a plurality of first yarns 31 arranged in the axial direction X and a plurality of second yarns 32 arranged in the circumferential direction of the liner 12. The plurality of first yarns 31 in the second fiber layer 62 are parallel to each other. The plurality of second yarns 32 in the second fiber layer 62 are parallel to each other. When the second fiber layer 62 is viewed from the lamination direction LD, the plurality of first yarns 31 constituting the second fiber layer 62 and the plurality of second yarns 32 constituting the second fiber layer 62 are orthogonal to each other.

[0033] The first yarn 31 is continuous between the first fiber layer 61 and the second fiber layer 62. The first yarn 31 of the present embodiment is continuous between all the fiber layers 51 laminated in the lamination direction LD. The second fiber layer 62 includes an entanglement portion 63 where the second yarn 32 is entangled with the first yarn 31. Since the second fiber layer 62 of the present embodiment is formed by plain weaving, it has the entanglement portion 63 as many as the number of intersection points where the second yarn 32 intersects with the first yarn 31. Since the first fiber layer 61 does not include the entanglement portion 63, the second fiber layer 62 of the present embodiment has more entanglement portions 63 than the first fiber layer 61.

[0034] [Structure of the dome fiber layer] As shown in FIG. 3, a plurality of dome fiber layers 52 are laminated in the lamination direction LD with respect to the dome outer surface 14a. The dome fiber layer 52 of the present embodiment is a fabric 60 including a first yarn 31 and a second yarn 32. The dome fiber layer 52 of the present embodiment is a single-layer fabric formed by plain weaving. Each of the first yarn 31 and the second yarn 32 arranged on the dome outer surface 14a is curved along the dome outer surface 14a while maintaining the yarn main axis direction on the body outer surface 13a.

[0035] The plurality of dome fiber layers 52 may be joined in the lamination direction LD by an interlayer binding yarn (not shown). Also, the plurality of dome fiber layers 52 may be joined to each other by an interlayer binding yarn (not shown). In this case, for example, two dome fiber layers 52 overlapping in the lamination direction LD are joined by an interlayer binding yarn. Thereby, in the plurality of dome fiber layers 52, a plurality of sets of dome fiber layers 52 joined by the interlayer binding yarn may be located.

[0036] In the present embodiment, the first yarn 31 is continuous among all the dome fiber layers 52 laminated in the lamination direction LD. Since the second yarn 32 is continuous between the fiber layer 51 and the dome fiber layer 52, the dome fiber layer 52 is integrated with the fiber layer 51.

[0037] [Method for manufacturing fiber structure] Next, a method for manufacturing the fiber structure 19 will be described with reference to FIGS. 9 and 10. As shown in FIG. 9, the fiber structure 19 is manufactured while the liner 12 is rotated about the central axis L as the rotation center. Thereby, the fiber structure 19 wound around the liner 12 is manufactured. The first yarn 31 is used as a warp yarn. The second yarn 32 is used as a weft yarn. The plurality of first yarns 31 are supplied from a warp beam toward the liner 12. By moving the first yarn 31 up and down by a heddle frame, an opening of the first yarn 31 is formed.

[0038] The ends of the plurality of first yarns 31 drawn from the warp beam are fixed to the outer surface 13a of the body and the outer surface 14a of the dome. The first yarn 31 whose end is fixed to the outer surface 14a of the dome is called the dome warp 31a. The first yarn 31 whose end is fixed to the outer surface 13a of the body is called the body warp 31b.

[0039] When forming the dome fiber layer 52, the second yarn 32 is inserted into the opening of the dome warp 31a. The second yarn 32 is entangled with the dome warp 31a. The formation of the opening of the dome warp 31a, the weft insertion of the second yarn 32 into the opening of the dome warp 31a, and the reed beating operation by the reed are repeated while being performed. Thereby, the dome fiber layer 52 is woven on the outer surface 14a of the dome. The dome fiber layer 52 is formed by a plain weave of the first yarn 31 and the second yarn 32.

[0040] While the liner 12 is being rotated, the weft insertion of the second yarn 32 into the opening of the dome warp 31a is repeated. Thereby, a plurality of dome fiber layers 52 are laminated in the lamination direction LD with respect to the outer surface 14a of the dome. The formation of the dome fiber layer 52 is completed.

[0041] As the liner 12 rotates, the dome warp 31a is wound around the liner 12. Since the dome fiber layer 52 is formed using this dome warp 31a, the first yarn 31 is continuous in all the dome fiber layers 52.

[0042] Similar to the dome warp 31a, the body warp 31b is also wound around the liner 12. The fiber layer 51 is formed using this body warp 31b. Thereby, the first yarn 31 of the present embodiment is continuous in the first fiber layer 61 and the second fiber layer 62.

[0043] The formation of the fiber layer 51 is performed in parallel with the formation of the dome fiber layer 52. When forming the fiber layer 51 of the present embodiment, the second yarn 32 inserted into the opening of the dome warp 31a is inserted between the plurality of body warps 31b and the outer surface 13a of the body. The second yarn 32 is inserted in the order of the opening of the dome warp 31a constituting one dome fiber layer 52, between the plurality of body warps 31b and the outer surface 13a of the body, and the opening of the dome warp 31a constituting the other dome fiber layer 52. The second yarn 32 does not intertwine with the body warp 31b.

[0044] The second yarn 32 is repeatedly inserted between the plurality of body warps 31b and the outer surface 13a of the body. Thereby, a second yarn layer 61b is formed on the outer surface 13a of the body. A first yarn layer 61a is formed so as to overlap the second yarn layer 61b in the stacking direction LD. A first fiber layer 61 is formed as the innermost layer 51a.

[0045] After the formation of the innermost layer 51a, the second yarn 32 is repeatedly inserted between the plurality of body warps 31b and the first fiber layer 61. The second yarn 32 inserted between the plurality of body warps 31b and the first fiber layer 61 is the second yarn 32 inserted into the opening of the dome warp 31a, similar to the innermost layer 51a. These are alternately stacked in the stacking direction LD in the order of the second yarn layer 61b and the first yarn layer 61a. A plurality of first fiber layers 61 are stacked in the stacking direction LD with respect to the outer surface 13a of the body. The fiber layer 51 excluding the outermost layer 51b is formed as the first fiber layer 61.

[0046] In FIGS. 9 and 10, among the second yarns 32, the portion constituting the fiber layer 51 excluding the outermost layer 51b is illustrated by a broken line. Among the second yarns 32, the portion constituting the dome fiber layer 52 and the portion constituting the outermost layer 51b are illustrated by a solid line.

[0047] As shown in FIG. 10, when forming the outermost layer 51b, the second yarn 32 is inserted into the opening of the body warp 31b. The second yarn 32 inserted into the opening of the body warp 31b is the same second yarn 32 that is inserted into the opening of the dome warp 31a, similar to the fiber layer 51 other than the outermost layer 51b. The second yarn 32 constituting the outermost layer 51b is entangled with the body warp 31b. The formation of the opening of the body warp 31b and the weft insertion of the second yarn 32 into the opening of the body warp 31b are repeated while the reed beating operation by the reed is performed. Thereby, the second fiber layer 62 is woven as the outermost layer 51b. The second fiber layer 62 is formed by plain weaving of the first yarn 31 and the second yarn 32. The formation of the fiber layer 51 is completed. When the formation of the fiber layer 51 and the dome fiber layer 52 is completed, the manufacture of the fiber structure 19 is finished.

[0048] [Method of Resin Impregnation into Fiber Structure] Next, a method of resin impregnation into the fiber structure 19 will be described with reference to FIG. 11. As shown in FIG. 11, after forming the fiber structure 19 on the outer surface 12a of the liner, the precursor 10a provided with the fiber structure 19 is placed in the molding die 70. The matrix resin Ma is impregnated into the fiber structure 19 using the RTM method. Thereby, the pressure vessel 10 in which the outer surface 12a of the liner is covered with the fiber reinforced composite material 11 is manufactured.

[0049] Although not shown in the figure, the molding die 70 is composed of a plurality of members. By assembling these plurality of members, a sealed space S is partitioned and formed inside the molding die 70. The precursor 10a is placed in the sealed space S.

[0050] The molding die 70 is provided with a resin flow path 71 inside. Through the resin flow path 71, the matrix resin Ma is injected into the sealed space S. The matrix resin Ma is filled in the gap between the molding die 70 and the precursor 10a. Thereby, the dome fiber layer 52 is impregnated with the matrix resin Ma. In the fiber layer 51, the matrix resin Ma is sequentially impregnated from the outermost layer 51b to the innermost layer 51a.

[0051] After the impregnation of the matrix resin Ma into the fiber structure 19 is completed, the fiber structure 19 is heated by the mold 70 to a temperature suitable for thermosetting the matrix resin Ma. The temperature at this time is set to the curing temperature of the epoxy resin employed as the matrix resin Ma. By heating with the mold 70, the matrix resin Ma impregnated in the fiber structure 19 thermosets.

[0052] When the entire matrix resin Ma impregnated in the fiber structure 19 thermosets, the fiber reinforced composite material 11 is formed. The manufacturing of the pressure vessel 10 provided with the fiber reinforced composite material 11 is completed. The pressure vessel 10 is taken out of the mold 70 after being cooled.

[0053] [Operation] Next, the operation of this embodiment will be described. In this embodiment, the second fiber layer 62 includes more entanglement portions 63 where the second yarn 32 is entangled with the first yarn 31 than the first fiber layer 61. The first fiber layer 61 constitutes the fiber layer 51 other than the outermost layer 51b. The second fiber layer 62 constitutes the outermost layer 51b.

[0054] The matrix resin Ma is filled in the gap between the mold 70 and the precursor 10a. At this time, the fiber layer 51 located in the outermost layer 51b receives the impregnation resistance of the matrix resin Ma. In this embodiment, the outermost layer 51b that receives such impregnation resistance of the matrix resin Ma has more entanglement portions 63 than the fiber layer 51 other than the outermost layer 51b. Therefore, in the outermost layer 51b, meandering of the reinforcing fibers due to the impregnation resistance of the matrix resin Ma is less likely to occur.

[0055] The first fiber layer 61 of the present embodiment has a so-called crimp press structure in which the second yarn 32 is not entangled with the first yarn 31. In other words, the entanglement portion 63 included in the first fiber layer 61 is less than that of the second fiber layer 62. When the matrix resin Ma is impregnated into the fiber structure 19, the impregnation resistance of the matrix resin Ma is weakened by acting on the outermost layer 51b. Thereafter, the impregnation resistance of the matrix resin Ma acts on the fiber layers 51 other than the outermost layer 51b. Therefore, in the fiber layers 51 other than the outermost layer 51b, the meandering of the reinforcing fibers due to the impregnation resistance of the matrix resin Ma is less likely to occur.

[0056] The second yarn 32 in the first fiber layer 61 does not meander due to the entanglement of the second yarn 32 with the first yarn 31. Therefore, the strength of the fiber reinforced composite material 11 can be improved without increasing the total number or thickness of the first yarn 31 and the second yarn 32 constituting the fiber structure 19. According to the present embodiment, by setting the fiber layer 51 other than the outermost layer 51b as the first fiber layer 61, an increase in the weight of the fiber reinforced composite material 11 can be suppressed.

[0057] [Effect] In the above first embodiment, the following effects can be obtained. (1) According to the above embodiment, the outermost layer 51b is constituted by the second fiber layer 62. The second fiber layer 62 includes more entanglement portions 63 where the second yarn 32 is entangled with the first yarn 31 than the first fiber layer 61. Therefore, in the second fiber layer 62, meandering of the reinforcing fibers due to the impregnation resistance of the thermosetting resin is less likely to occur. Accordingly, in the fiber reinforced composite material 11 formed from the fiber structure 19, a decrease in the pressure resistance and fatigue characteristics can be suppressed. According to the above embodiment, the number of entanglement portions 63 provided in the first fiber layer 61 is less than that in the second fiber layer 62. Therefore, compared with the second fiber layer 62, the first fiber layer 61 has less meandering of the second yarn 32 due to the entanglement of the second yarn 32 with the first yarn 31. By providing the plurality of fiber layers 51 with the first fiber layer 61, the strength of the fiber reinforced composite material 11 formed using the fiber structure 19 can be improved. Even if the total number of the first yarn 31 and the second yarn 32 constituting the fiber structure 19 is not increased or the thickness is not increased, the strength of the fiber reinforced composite material 11 can be improved, so that an increase in the weight of the fiber reinforced composite material 11 can be suppressed. Accordingly, in the fiber reinforced composite material 11 formed from the fiber structure 19, the strength can be improved while suppressing a decrease in the pressure resistance and fatigue characteristics and an increase in the weight.

[0058] (2) The first yarn 31 is continuous between the first fiber layer 61 and the second fiber layer 62. Therefore, the strength of the fiber structure 19 in the yarn main axis direction of the first yarn 31 can be improved as compared with the case where the first yarn 31 constituting the first fiber layer 61 and the first yarn 31 constituting the second fiber layer 62 are not continuous with each other. Accordingly, the strength of the fiber reinforced composite material 11 formed from the fiber structure 19 can be further improved.

[0059] (Second Embodiment) Hereinafter, a second embodiment in which the fiber structure 19 is embodied will be described with reference to FIGS. 4, 8, and 12. The second embodiment is different from the first embodiment in that the first fiber layer 61 does not include the first yarn layer 61a and the second yarn layer 61b. Centering on such differences, the following description will be given. For the same configurations as those in the first embodiment, the same reference numerals as those in the first embodiment will be given and the description will be omitted as appropriate.

[0060] [Structure of Fiber Structure] As shown in FIGS. 4 and 12, the first fiber layer 61 of the present embodiment does not include the first yarn layer 61a and the second yarn layer 61b in the first embodiment. The first fiber layer 61 is a fabric 60 in which the second yarn 32 is entangled with the first yarn 31. That is, the first fiber layer 61 and the second fiber layer 62 are made of the fabric 60. The first fiber layer 61 and the second fiber layer 62 of the present embodiment include an entanglement portion 63 in which the second yarn 32 is entangled with the first yarn 31. The first fiber layer 61 of the present embodiment is formed by twill weaving. For example, the second yarn 32 in the first fiber layer 61 is entangled with the first yarn 31 every other one.

[0061] The first fiber layer 61 is composed of the first yarn 31 and the second yarn 32. In the first yarn 31 of the first fiber layer 61, the first yarn spindle direction W1 coincides with the circumferential direction centered on the central axis L. In the second yarn 32 of the first fiber layer 61, the second yarn spindle direction W2 coincides with the axial direction X. That is, the second yarn 32 extends in a yarn spindle direction different from that of the first yarn 31. A plurality of the first yarns 31 in the first fiber layer 61 are arranged in parallel with each other in the axial direction X. A plurality of the second yarns 32 in the first fiber layer 61 are arranged in parallel with each other in the circumferential direction of the liner 12. When the first fiber layer 61 is viewed from the lamination direction LD, the plurality of first yarns 31 constituting the first fiber layer 61 and the plurality of second yarns 32 constituting the first fiber layer 61 are orthogonal to each other. The first yarn 31 is continuous between the first fiber layer 61 and the second fiber layer 62.

[0062] The dome fiber layer 52 of the present embodiment is a fabric 60 including the first yarn 31 and the second yarn 32, similarly to the first embodiment. The dome fiber layer 52 of the present embodiment is a single-layer fabric formed by plain weaving. The first yarn 31 is continuous between all the dome fiber layers 52 laminated in the lamination direction LD. The second yarn 32 is continuous between the fiber layer 51 and the dome fiber layer 52.

[0063] [Comparison of Entanglement Portion between First Fiber Layer and Second Fiber Layer] As shown in FIGS. 8 and 12, the second fiber layer 62 of the present embodiment is a single-layer fabric formed by plain weaving in the same manner as in the first embodiment. Therefore, the second fiber layer 62 of the present embodiment has entanglement portions 63 corresponding to the number of intersections where the second yarn 32 intersects the first yarn 31. The second fiber layer 62 of the present embodiment has more entanglement portions 63 than the first fiber layer 61.

[0064] [Method for manufacturing fiber structure] As shown in FIGS. 4 and 12, when forming the first fiber layer 61 of the present embodiment, the second yarn 32 is repeatedly inserted into the opening of the body warp 31b. Thereby, the first fiber layer 61 is formed as the innermost layer 51a. A plurality of first fiber layers 61 are laminated in the lamination direction LD with respect to the outer surface 13a of the body. The fiber layer 51 excluding the outermost layer 51b is formed as the first fiber layer 61. The second fiber layer 62 and the dome fiber layer 52 are formed in the same manner as in the first embodiment. When the formation of the fiber layer 51 and the dome fiber layer 52 is completed, the manufacturing of the fiber structure 19 is completed. By impregnating the fiber structure 19 with the matrix resin Ma using the RTM method in the same manner as in the first embodiment, a pressure vessel 10 in which the outer surface 12a of the liner is covered with the fiber reinforced composite material 11 is manufactured.

[0065] [Function] Next, the function of the present embodiment will be described. In the present embodiment, the second fiber layer 62 has more entanglement portions 63 where the second yarn 32 intersects the first yarn 31 than the first fiber layer 61. The first fiber layer 61 constitutes the fiber layer 51 other than the outermost layer 51b. The second fiber layer 62 constitutes the outermost layer 51b. Therefore, as in the first embodiment, in the fiber layer 51, meandering of the reinforcing fibers due to the impregnation resistance of the matrix resin Ma is less likely to occur.

[0066] The second yarn 32 in the first fiber layer 61 has less meandering due to the entanglement of the second yarn 32 with the first yarn 31 than the second yarn 32 in the second fiber layer 62. By setting the fiber layer 51 other than the outermost layer 51b as the first fiber layer 61, it is possible to improve the strength of the fiber reinforced composite material 11 while suppressing an increase in the weight of the fiber reinforced composite material 11.

[0067] [Effect] In the above-described second embodiment, the same effects as those of the first embodiment can be obtained. In addition, each of the above-described embodiments can be implemented with the following modifications. Each of the above-described embodiments and the following modification examples can be implemented in combination with each other within a technically non-conflicting range.

[0068] ○ As shown in FIG. 13, the first fiber layer 61 in the second embodiment may be formed by twill weaving. For example, in the first fiber layer 61 of this modification example, the second yarn 32 is entangled with the first yarn 31 every four. Also in this modification example, the first fiber layer 61 is a fabric 60 in which the second yarn 32 is entangled with the first yarn 31. That is, the first fiber layer 61 and the second fiber layer 62 are composed of the fabric 60. The first fiber layer 61 and the second fiber layer 62 of the present embodiment include an entanglement portion 63 where the second yarn 32 is entangled with the first yarn 31. The second fiber layer 62 is a single-layer fabric formed by plain weaving as in each of the above-described embodiments. The second fiber layer 62 has the entanglement portion 63 as many as the number of intersection points where the second yarn 32 intersects with the first yarn 31. Also in this modification example, the second fiber layer 62 includes more entanglement portions 63 than the first fiber layer 61. According to this modification example, the same effects as those of each of the above-described embodiments can be obtained.

[0069] ○ In the second embodiment, the second fiber layer 62 is not limited to being formed by plain weaving. For example, the second fiber layer 62 may be formed by twill weaving. In this case, for example, the first fiber layer 61 is formed by twill weaving. The second fiber layer 62 includes more entanglement portions 63 than the first fiber layer 61.

[0070] ○ In the first embodiment, the first fiber layer 61 may include at least one of the first yarn 31 and the second yarn 32. For example, either the first yarn layer 61a or the second yarn layer 61b may be omitted from the first fiber layer 61. In this case, the first fiber layer 61 includes either one of the first yarn 31 and the second yarn 32.

[0071] ○ The first yarn 31 does not have to be continuous between the first fiber layer 61 and the second fiber layer 62. ○ In the second embodiment, the types of some of the first fiber layers 61 and the other first fiber layers 61 may be different. Here, the case where the types of the first fiber layers 61 are different includes, for example, the case where the weaving method is different and the case where the yarns are different. When the weaving methods of some of the first fiber layers 61 and the other first fiber layers 61 are different, for example, some of the first fiber layers 61 may be twill weave and the other first fiber layers 61 may be damask weave. Also in this case, by forming the second fiber layer 62 by plain weave, the second fiber layer 62 includes more entanglement portions 63 than the first fiber layer 61. When the yarns of some of the first fiber layers 61 and the other first fiber layers 61 are different, for example, some of the first fiber layers 61 may include the first yarn 31 and the second yarn 32, and the other first fiber layers 61 may include either the first yarn 31 or the second yarn 32.

[0072] ○ As shown in FIGS. 14 and 15, in the first embodiment and the second embodiment, the second fiber layer 62 may be the fabric 75. That is, the second fiber layer 62 does not have to be the woven fabric 60. Specifically, the second fiber layer 62 of this modification example includes a plurality of first yarns 31 and a plurality of second yarns 32. The first yarn 31 and the second yarn 32 intersect each other. The first yarn 31 intersects, for example, the center line C parallel to the central axis L at a first angle A1. The second yarn 32 intersects, for example, the center line C at a second angle A2. For example, the first angle A1 is 60 degrees. For example, the second angle A2 is -60 degrees. The second fiber layer 62 of this modification example has as many entanglement portions 63 as the number of intersection points where the second yarn 32 intersects the first yarn 31. Also in this modification example, the second fiber layer 62 includes more entanglement portions 63 than the first fiber layer 61. According to this modification example, the same effects as those of the above embodiments can be obtained.

[0073] ○ In the first and second embodiments, the plurality of dome fiber layers 52 are not limited to being plain woven. For example, the plurality of dome fiber layers 52 may be composed of a fabric 60 other than plain weave. In this case, the plurality of dome fiber layers 52 are formed, for example, by twill weave or damask weave. For example, the plurality of dome fiber layers 52 may be composed of a dome fiber layer 52 made of a fabric 60 and a dome fiber layer 52 made of a composition 75 that covers the dome fiber layer 52 made of the fabric 60 from the outside.

[0074] ○ In the first and second embodiments, the second fiber layer 62 may constitute the innermost layer 51a. In this case, for example, the fiber layers 51 other than the innermost layer 51a may be constituted by the first fiber layer 61. As a method of impregnating the matrix resin Ma using the RTM method, there is a method of filling the matrix resin Ma between the outer surface 12a of the liner and the fiber structure 19. Such a method is, for example, to provide a resin passage connecting between the outer surface 12a of the liner and the fiber structure 19 at the base portion 15 of the liner 12. The matrix resin Ma is filled into the fiber structure 19 through this resin passage. At this time, the fiber layer 51 located in the innermost layer 51a receives the impregnation resistance of the matrix resin Ma. In this modified example, the innermost layer 51a that receives such impregnation resistance of the matrix resin Ma is the second fiber layer 62. The second fiber layer 62 has more entanglement portions 63 than the first fiber layer 61. Therefore, in the innermost layer 51a, meandering of the reinforcing fibers due to the impregnation resistance of the matrix resin Ma is less likely to occur. Note that both the innermost layer 51a and the outermost layer 51b may be constituted by the second fiber layer 62. In this case, the fiber layers 51 other than the innermost layer 51a and the outermost layer 51b may be constituted by the first fiber layer 61.

[0075] ○ The liner 12 may be made of metal. ○ The liner 12 and the base portion 15 may be integrally formed. ○ The pressure vessel 10 is not limited to being mounted and used as a hydrogen source for a fuel cell - equipped electric vehicle. For example, it may be applied to a hydrogen source for a hydrogen engine, a heat pump, etc. Also, it may be used as a hydrogen source for a fuel cell of a household power supply.

[0076] ○ The pressure vessel 10 is not limited to containing hydrogen gas. The pressure vessel 10 may contain other gases such as, for example, compressed natural gas (CNG) or liquefied natural gas (LNG). ○ The fiber structure 19 may have a shape other than the cylindrical body 20. That is, the fiber structure 19 only needs to include the cylindrical body 20. For example, the fiber structure 19 does not necessarily need to include at least one of a dome fiber layer 52 located in the axial direction X from the cylindrical body 20 and a dome fiber layer 52 located in the direction opposite to the axial direction X from the cylindrical body 20. For example, the fiber structure 19 may include a layer of fibers different from the dome fiber layer 52 in at least one of the axial direction X from the cylindrical body 20 and the direction opposite to the axial direction X from the cylindrical body 20.

[0077] ○ The fiber structure 19 may be a fiber preform 19a applied to other than the pressure vessel 10.

Description of Reference Numerals

[0078] LD…Laminating direction, W1…First yarn main axis direction, W2…Second yarn main axis direction, 11…Fiber reinforced composite material, 19…Fiber structure, 20…Cylindrical body, 20a…Inner surface, 20b…Outer surface, 31…First yarn, 32…Second yarn, 51…Fiber layer, 51a…Innermost layer, 51b…Outermost layer, 60…Fabric, 61…First fiber layer, 62…Second fiber layer, 63…Interlaced portion.

Claims

1. A fiber structure for forming a fiber-reinforced composite material by impregnating a thermosetting resin using the RTM method, wherein the fiber structure includes a cylindrical tube, the tube includes a plurality of fiber layers laminated on one another in the lamination direction, the plurality of fiber layers include, a first fiber layer including at least one of a first yarn and a second yarn extending in a yarn spindle direction different from that of the first yarn, a second fiber layer including the first yarn and the second yarn, the first yarn and the second yarn are made of reinforcing fibers, the first fiber layer does not include an entanglement portion where the second yarn is entangled with the first yarn, when the fiber layer constituting the inner surface of the tube is defined as the innermost layer and the fiber layer constituting the outer surface of the tube is defined as the outermost layer, the second fiber layer constitutes at least one of the innermost layer and the outermost layer and includes the entanglement portion, the first fiber layer constitutes a fiber layer that acts after the impregnation resistance of the thermosetting resin is weakened by the second fiber layer. The fiber structure is characterized by this.

2. A fiber structure for forming a fiber-reinforced composite material by impregnating a thermosetting resin using the RTM method, wherein the fiber structure includes a cylindrical tube, the tube includes a plurality of fiber layers laminated on one another in the lamination direction, the plurality of fiber layers include, a first fiber layer including a first yarn and a second yarn extending in a yarn spindle direction different from that of the first yarn, a second fiber layer including the first yarn and the second yarn, the first yarn and the second yarn are made of reinforcing fibers, the first fiber layer and the second fiber layer include an entanglement portion where the second yarn is entangled with the first yarn, at least one of the first fiber layer and the second fiber layer is made of a woven fabric, when the fiber layer constituting the inner surface of the tube is defined as the innermost layer and the fiber layer constituting the outer surface of the tube is defined as the outermost layer, the second fiber layer constitutes at least one of the innermost layer and the outermost layer and includes more of the entanglement portion than the first fiber layer, the first fiber layer constitutes a fiber layer that acts after the impregnation resistance of the thermosetting resin is weakened by the second fiber layer. The fiber structure is characterized by this.

3. The first fiber layer includes the first yarn, The fiber structure according to claim 1 or claim 2, wherein the first yarn is continuous between the first fiber layer and the second fiber layer.

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