JP2011042887A - Three-dimensional braiding, fiber reinforced composite material, and method for producing fiber reinforced composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a three-dimensional braiding that is lightweight, has high energy absorption, is stably broken, and is suitable for a crush member, and a fiber-reinforced composite material. <P>SOLUTION: The three-dimensional braiding 11 includes four or more layers of core yarn layers 13 made of core yarns 12 extending in the axial direction, and through yarns 14a and 14b formed so as to pass through the core yarn layers 13, and is formed in a cylindrical shape. Through yarns 14a pass through adjacent core yarn layers 13 so as to be folded back. The peel strength of a selected core yarn layer 13 among the core yarn layers 13 provided between the outermost layer and the innermost layer is less than the peel strength of the other core yarn layers 13. The three-dimensional braiding 11 is preferably impregnated with a resin to be cured, and used as a fiber-reinforced composite material for constituting a crush member. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a three-dimensional braiding, a fiber reinforced composite material, and a method for manufacturing a fiber reinforced composite material, and more particularly, a three-dimensional braiding suitable for an energy absorbing member applied around a bumper of an automobile, around an aircraft seat, and the like. The present invention relates to a fiber-reinforced composite material and a method for producing a fiber-reinforced composite material.

  It is known that a fiber-reinforced composite material has an excellent energy absorbing ability as an energy absorbing member that absorbs energy by breaking when receiving an excessive impact load. The fiber reinforced composite material is usually formed of a laminate of prepregs, but in recent years, a material that enhances energy absorption capability by using an interlayer penetration yarn or a material that uses three-dimensional braiding has been proposed. When the energy absorbing member is used in, for example, a crash box disposed between a bumper and a body frame, the crash box usually has a required mechanical strength enough to maintain its own posture, and exceeds the design value. When an impact load is applied, it is required to be deformed and destroyed while absorbing the impact load.

  An energy absorbing member formed by laminating prepregs has a large amount of work for manufacturing and has a poor raw material yield. In addition, since the reinforcing fibers are not continuous between the laminated prepreg layers, it is necessary to laminate more than the number of single sheets originally required as a crash box in order to obtain the necessary self-holding strength. In order to solve this problem, shock absorbers for crash boxes (fibrous reinforced resin obtained by impregnating resin into a reinforcing fiber braid obtained by flattening a tubular body knitted by the braiding method into a three-dimensional shape (energy) Absorbing member) has been proposed (see Patent Document 1).

  In addition, an energy absorbing member has been proposed that causes local breakage or deformation starting from the end of the member and efficiently absorbs high energy using the local breakage or deformation (see Patent Document 2). As shown in FIG. 5 (a), the energy absorbing member 41 has a plurality of reinforcing fiber layers 42a, 42b, 42c, and 42d impregnated with resin, and between the reinforcing fiber layers 42a to 42d, Resins 43a, 43b, and 43c having higher elongation than the resin that is combined with the reinforcing fiber layers 42a to 42d are disposed. The reinforcing fiber layers 42a to 42d are formed of prepregs in which reinforcing fibers are impregnated with resin. In the energy absorbing member 41, the resin 43b is disposed at the center portion in the thickness direction, and the resin 43b is not reinforced with reinforcing fibers, and therefore is weaker in strength than the adjacent reinforcing fiber layers 42b and 42c. As shown in FIG. 6B, the bending deformation or destruction starts smoothly from the center to both sides with respect to the compressive load P, and the bending deformation or destruction starts smoothly.

JP 2009-107408 A JP-A-6-307478

  When three-dimensional braiding is used for the crush material, depending on the strength of the fiber that penetrates between the layers, as shown in FIG. There is a problem that it is bent in the middle and is broken in the shape of a "<", and the absorbed energy is small and the fracture mode is not stable.

  On the other hand, the energy absorbing member of Patent Document 2 needs to be laminated by interposing high-strength resins 43a, 43b, and 43c between a plurality of prepregs constituting the reinforcing fiber layers 42a to 42d. While having the problem of the general energy absorption member formed by laminating | stacking a prepreg, there exists a problem that the work amount at the time of laminating | stacking a prepreg becomes more.

  The present invention has been made in view of the above-described conventional problems, and the object thereof is a three-dimensional braiding and fiber-reinforced composite material suitable for a crash member that is lightweight and capable of absorbing high energy and capable of stable fracture. And it is providing the manufacturing method of a fiber reinforced composite material.

  In order to achieve the above-mentioned object, the invention according to claim 1 is formed into a cylindrical shape from a core yarn layer formed of a core yarn extending in the axial direction and a penetrating yarn organized so as to penetrate the core yarn layer. 3D braiding formed. The core yarn layer is provided with four or more layers, and the penetrating yarn has a structure which is formed so as to be folded back through two adjacent core yarn layers. Among the core yarn layers provided between the outermost core yarn layer and the innermost core yarn layer, the strength of the selected core yarn layer or the strength at which the selected adjacent core yarn layers peel is different. It is weaker than the peel strength between adjacent core yarn layers. Here, the “thread” of the core yarn or the penetrating thread means a fiber bundle in which the fibers are aligned without being twisted or a thread in which the fibers are twisted, and impregnating and curing the resin to strengthen the fiber. When used as a composite material, a fiber bundle is preferred. The core yarn layer is adjacent in a direction perpendicular to the surface formed by the core yarn layer.

  The three-dimensional braiding of the present invention is preferably used as a fiber-reinforced composite material by impregnating and curing a resin. When the fiber reinforced composite material is used as an energy absorbing member, the fiber reinforced composite material is used in a state where an excessive impact load (compressive load) is applied from the axial direction of the three-dimensional braiding serving as a reinforced fiber to the fiber reinforced composite material. When three-dimensional braiding is formed without positively changing the strength of each core yarn layer and the strength of peeling between the core yarn layers, when an excessive impact load is applied to the energy absorbing member, the member There is a case in which the member is bent and broken from the middle of the member without being bent and deformed so as to tear from the end of the member in the thickness direction. However, when the three-dimensional braiding of the present invention is used, when an excessive impact load is applied to the energy absorbing member, the core yarn layer having a weak strength or the core yarn layer having a weak strength to be peeled off at the end of the member. Since the energy absorbing member is bent so as to be torn in the thickness direction from the portion, and is sequentially deformed and broken, the impact energy is efficiently absorbed. Therefore, the three-dimensional braiding according to the present invention is suitable for a crash member that is lightweight and capable of absorbing high energy and capable of stable fracture.

  According to a second aspect of the present invention, in the first aspect of the present invention, the strength of the penetrating thread that penetrates the selected core yarn layer is formed to be weaker than the strength of the other penetrating thread. In the fiber reinforced composite material using the three-dimensional braiding of the present invention as a reinforcing fiber, when an excessive impact load is applied to the energy absorbing member, it tears in the thickness direction from the end corresponding to the portion where the strength of the penetrating yarn is weak It bends in such a way that it is successively deformed and destroyed, and the impact energy is absorbed efficiently.

  According to a third aspect of the invention, in the first or second aspect of the invention, the three-dimensional braiding is formed with a weak center in the thickness direction. Here, the “thickness direction” means a direction orthogonal to the axial direction of the cylindrical three-dimensional braiding. The “center in the thickness direction” means a portion of a penetrating thread that penetrates between the two core yarn layers when the core yarn layer is an even number, and a center core yarn layer when the core yarn layer is an odd number. It becomes part of. In the fiber reinforced composite material using the three-dimensional braiding of the present invention as a reinforcing fiber, when an excessive impact load is applied to the energy absorbing member, the state is symmetrical from the central portion in the thickness direction on the end surface of the energy absorbing member. Then, it bends and tears in the thickness direction, and it is sequentially deformed and destroyed. Therefore, compared with the case where the energy absorbing member is deformed so as to be torn in a left-right asymmetric state, the breakage is likely to proceed stably and the impact energy is absorbed more efficiently.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the core yarn and the penetrating yarn are all made of the same kind of material and constitute the selected core yarn layer. Or the penetrating thread that penetrates the selected adjacent core thread layer is thin. In the present invention, the three-dimensional braiding can be reduced in weight and thickness as long as the number of yarns is the same as compared with the case where the core yarn and the penetrating yarn are all formed of the same thickness.

  The invention according to claim 5 is the invention according to claim 1 or claim 3, wherein the number of penetrating yarns that fold through the selected core yarn layer or the selected adjacent core yarn layer is different. The number of penetrating yarns is less than the number of penetrating yarns that pass through the core yarn layer and turn back. In the present invention, it is possible to reduce the weight and cost of the three-dimensional braiding, and hence the fiber reinforced composite material, simply by reducing the number of penetrating yarns set in the three-dimensional braiding apparatus when manufacturing the three-dimensional braiding.

  The invention described in claim 6 is a fiber-reinforced composite material using the three-dimensional braiding described in any one of claims 1 to 5 as a reinforcing fiber. In this invention, the same effect as that of any one of claims 1 to 5 can be obtained.

  The manufacturing method of the fiber-reinforced composite material of the invention described in claim 7 is the three-dimensional braiding according to any one of claims 1 to 5 on the outside of the mandrel using a three-dimensional braiding device. A three-dimensional braid forming step for forming the mandrel, a mandrel removing step for removing the mandrel from the inside of the formed three-dimensional braiding, and a resin impregnation curing step for impregnating and curing the resin in the three-dimensional braid from which the mandrel has been removed And. Therefore, the three-dimensional braiding is formed in a shape corresponding to the shape of the mandrel to be used, and is not limited to a cylindrical shape having a constant diameter, for example, it may be formed in a cylindrical shape (conical frustum shape) whose diameter changes in the axial direction. it can. In 3D braiding, the resin impregnation and curing process is not necessarily performed in the resin impregnation and curing process with the shape when the mandrel is removed, but it is changed to a shape other than the cylindrical shape depending on the shape of the mold used for the impregnation and curing. can do.

  According to the first to fifth aspects of the invention, it is possible to provide a three-dimensional braiding suitable for a crash member that is lightweight and capable of absorbing high energy and capable of stable fracture. According to the invention described in Item 7, it is possible to provide a fiber-reinforced composite material suitable for a crash member that is lightweight and capable of absorbing high energy and capable of stable fracture.

(A) is a schematic perspective view of the three-dimensional braiding of one embodiment, (b) is a partial schematic view seen from the axial direction showing the tissue state of the three-dimensional braiding. (A) is a schematic diagram which shows the state in which an energy absorption member is destroyed, (b) is a schematic diagram which shows the part which a penetration thread is easy to fracture | rupture. The partial schematic diagram which shows the structure | tissue state of the three-dimensional braiding of another embodiment. The partial schematic diagram which shows the structure | tissue state of the three-dimensional braiding of another embodiment. (A) is a fragmentary sectional view of the energy absorption member of a prior art, (b) is a fragmentary sectional view which shows the state in which an energy absorption member is destroyed. The schematic diagram which shows the destruction state of another energy absorption member.

Hereinafter, an embodiment embodying the present invention will be described with reference to FIGS. 1 and 2.
As shown in FIG. 1A, the three-dimensional braiding 11 is formed in a cylindrical shape. As shown in FIG. 1B, the three-dimensional braiding 11 passes through the core yarn layer 13 formed of the core yarn 12 extending in the axial direction (direction orthogonal to the paper surface) and the core yarn layer 13. The core thread layers 13 are provided in five layers, which are composed of structured penetrating threads 14a and 14b. The penetrating thread includes a penetrating thread 14a structured so as to fold through two adjacent core thread layers 13, and an outermost layer (first layer in this embodiment) or innermost layer (fifth layer in this embodiment). ) Only through the thread 14b. And the selected core yarn layer 13 of the core yarn layers 13 provided between the outermost layer (first layer in this embodiment) and the innermost layer (fifth layer in this embodiment) of the core yarn layer 13. (In this embodiment, between the second and third core yarn layers 13 and between the third and fourth core yarn layers 13), the peel strength between the other core yarn layers 13 It is formed so as to be weaker than the strength to be applied. The axial direction of the three-dimensional braiding 11 is the axial direction of the cylinder in FIG. Further, the thickness direction of the three-dimensional braiding 11 is a direction orthogonal to the central axis of the cylinder in FIG. 1A, and the vertical direction in FIG.

  More specifically, the core yarn 12 and the penetrating yarns 14a and 14b are all composed of untwisted fiber bundles made of the same kind of material, and the fiber bundle formed with low strength reduces the number of fibers constituting the fiber bundle. By reducing the thickness, the strength is weakened. In this embodiment, untwisted fiber bundles made of carbon fibers are used for the core yarn 12 and the penetrating yarns 14a and 14b. In the carbon fiber bundle, hundreds to tens of thousands of thin fibers are bundled to form one fiber bundle, and the fiber bundle having the number of fibers suitable for the required performance is selected. Among the penetrating yarns 14a structured so as to fold through the two adjacent core yarn layers 13, the penetrating yarn 14a structured so as to fold through the second and third core yarn layers 13 Alternatively, a fiber bundle thinner than the other penetration threads 14a and 14b, that is, a fiber bundle having a lower strength, is used for the penetration thread 14a that is structured so as to be folded back through the third and fourth core thread layers 13. ing. In addition, a fiber bundle having the same thickness as that of the penetrating yarn 14b is used for the core yarn 12.

  In FIG. 1B, for the sake of illustration, the penetrating yarns 14a and 14b are drawn so as to be folded back in the same plane, but they are not actually arranged in the same plane, and penetrate the paper surface. It is arranged in a state extending in the direction. Further, the core yarn 12 and the penetrating yarns 14a and 14b form a three-dimensional braiding 11 in a state where the filaments constituting the fiber bundle are expanded and the fiber bundle is flat. For example, the fiber bundle is organized in a state where the width is expanded to about 10 mm.

  The three-dimensional braiding 11 is used as a reinforcing fiber of a fiber-reinforced composite material using a thermosetting resin as a matrix resin. For example, an epoxy resin is used as the thermosetting resin.

  The three-dimensional braiding 11 is organized using a three-dimensional braiding device (three-dimensional braider). For example, a braid structure in a state in which the core yarn 12 and the penetrating yarns 14a and 14b are wound around the outside of the mandrel using a mandrel that has a hollow portion shape of the three-dimensional braiding 11 to be formed and can be divided into a plurality of parts. The three-dimensional braiding 11 is formed around the mandrel by forming (three-dimensional braiding forming step). After the three-dimensional braiding 11 is formed to a predetermined length, the three-dimensional braiding 11 is removed from the three-dimensional braider together with the mandrel. And a mandrel is removed from the inner side of the three-dimensional braiding 11 (mandrel removal process). As a result, the three-dimensional braiding 11 is completed.

  The formed three-dimensional braiding 11 is impregnated and cured with a thermosetting resin in a resin impregnation and curing step to form a fiber reinforced composite material that becomes an energy absorbing member. The resin is impregnated and cured by, for example, an RTM (resin transfer molding) method.

  Next, the operation of the fiber-reinforced composite material configured as described above will be described. The fiber reinforced composite material receives an impact load (compression load) from the axial direction and is used as a crash member that absorbs energy by breaking when receiving an excessive impact load. When the three-dimensional braiding 11 is formed without positively changing the strength of each core yarn layer 13 and the strength of peeling between the core yarn layers 13, when an excessive impact load is applied to the crash member, As shown in FIG. 6, the crash member is bent and broken from the middle, the absorbed energy is reduced, and the fracture mode is not stable.

  However, the three-dimensional braiding 11 of this embodiment is a thread that is structured to fold through the second and third core yarn layers 13 or the third and fourth core yarn layers 13. 14a is comprised by the fiber bundle weaker than the other penetration yarns 14a and 14b. The strength at which the adjacent core yarn layers 13 are peeled off depends on the strength of the penetrating yarns 14a and 14b that exist in a state of passing through the adjacent core yarn layers 13 and turning back. When a compressive load acts on the crash member, the compressive load acts as a tensile force on the penetrating threads 14a and 14b. Then, the penetrating yarn 14a that folds through the second and third core yarn layers 13 or the third and fourth core yarn layers 13 breaks at the portion indicated by the arrow Y in FIG. It becomes easy. As a result, the peel strength between the second and third core yarn layers 13 or between the third and fourth core yarn layers 13 is relatively weaker than the peel strength at other portions. .

  As shown in FIG. 2 (a), when an excessive impact load F is applied to the crash member 20, the crash member 20 has cracks at the end portions where the strength between the core yarn layers 13 is weak. It is generated, bent so as to tear in the thickness direction from the end, and successively deformed and broken. The peel strength between the second and third core yarn layers 13 or between the third and fourth core yarn layers 13 is not completely the same. The member 20 starts to break from the second layer and the third core yarn layer 13 or between the third layer and the fourth core yarn layer 13 and proceeds. As a result, the crash member 20 does not bend and break from the middle, but is bent so as to tear in the thickness direction from its end portion, so that the progressive deformation fracture proceeds, so that the impact energy is efficiently absorbed and the energy absorption amount Will increase.

According to this embodiment, the following effects can be obtained.
(1) The three-dimensional braiding 11 has a cylindrical shape from five core yarn layers 13 formed of core yarns 12 extending in the axial direction and penetrating yarns 14a and 14b organized so as to penetrate the core yarn layer 13. Is formed. The penetrating thread includes a penetrating thread 14a that is structured to fold through adjacent core thread layers 13 and a penetrating thread 14b that is structured to fold through only the outermost or innermost core thread layer 13. And the strength of peeling between selected core yarn layers 13 among the core yarn layers 13 provided between the outermost layer and the innermost layer is weaker than the strength of peeling between the other core yarn layers 13. The three-dimensional braiding 11 is used as a reinforcing fiber of a fiber-reinforced composite material that is used as an energy absorbing member (crash member 20) that is broken and absorbs impact energy when an excessive impact load (compression load) F is applied, And it is used in the state where an excessive impact load is applied from the axial direction of the three-dimensional braiding 11. When the crash member 20 is subjected to an excessive impact load F, at its end, the crush member 20 is bent so as to tear in the thickness direction from a portion where the strength between the core yarn layers 13 is weak. Absorbs impact energy efficiently. Therefore, the three-dimensional braiding 11 is suitable for the crash member 20 that is lightweight and capable of absorbing high energy and capable of stable destruction.

  (2) The three-dimensional braiding 11 penetrates through the selected core yarn layers 13 (the second and third core yarn layers 13 and the third and fourth core yarn layers 13). The strength of the yarn 14 a is formed to be weaker than the strength of the other penetration yarns 14 a and 14 b, and the strength to peel between the selected core yarn layers 13 is weaker than the strength to peel between the other core yarn layers 13. . Therefore, the target three-dimensional braiding 11 can be formed simply by changing the fiber bundle of the penetrating yarn 14a to a fiber bundle having a lower strength than the other penetrating yarns 14a and 14b.

  (3) In the three-dimensional braiding 11, the core yarn 12 and the penetrating yarns 14a and 14b are all made of the same kind of material, and the selected core yarn layer 13 (the second and third core yarn layers 13 and the third layer). The thickness of the penetrating thread 14a that folds through the layer and the fourth core thread layer 13) is thin. Therefore, as compared with the case where the core yarn 12 and the penetrating yarns 14a and 14b are all formed of the same thickness yarn (fiber bundle), if the number of yarns is the same, the three-dimensional braiding 11 is reduced in weight and thickness. Can be achieved.

  (4) The fiber-reinforced composite material constituting the crash member 20 uses the three-dimensional braiding 11 described in (1) to (3) as reinforcing fibers. Therefore, effects corresponding to (1) to (3) can be obtained.

  (5) A method for producing a fiber-reinforced composite material includes a three-dimensional braiding forming step of forming a three-dimensional braiding 11 on the outside of a mandrel using a three-dimensional braiding apparatus, and the formed three-dimensional braiding 11 A mandrel removing step for removing the mandrel from the inside of the substrate, and a resin impregnating and curing step for impregnating and curing the resin in the three-dimensional braiding 11 from which the mandrel has been removed. Therefore, the three-dimensional braiding 11 is formed in a shape corresponding to the shape of the mandrel to be used, and the cylindrical three-dimensional braiding 11 can be easily formed. The three-dimensional braiding can be formed into a fiber-reinforced composite material having a shape corresponding to the shape of the mold used for the impregnation and curing in the resin impregnation and curing step.

  (6) Since carbon fibers are used as the core yarn 12 and the penetrating yarns 14a and 14b constituting the three-dimensional braiding 11, the weight can be reduced with the same impact strength and the weight is the same. The impact strength can be improved.

The embodiment is not limited to the above, and may be configured as follows, for example.
The three-dimensional braiding 11 only needs to have four or more core yarn layers 13, and the number of the core yarn layers 13 is not limited to an odd number and may be an even number. For example, as shown in FIG. 3, the three-dimensional braiding 11 may be configured to have four core yarn layers 13. When the number of the core yarn layers 13 is an even number, the center in the thickness direction of the three-dimensional braiding 11 is the core yarn layer 13 of two layers (the second layer and the third layer in this embodiment) at the center portion in the thickness direction. Between. The penetrating thread 14a that folds through between the two core thread layers 13 at the center in the thickness direction is folded back through the other two core thread layers 13 (the first layer and the fourth layer in this embodiment). When weaker than the penetrating thread 14a, the strength at which the two core yarn layers 13 in the central portion in the thickness direction peel is weaker than the strength at which the other two core yarn layers 13 peel. In this case, the crash member 20 formed of a fiber-reinforced composite material using the three-dimensional braiding 11 as a reinforcing fiber is always provided with a second layer that is two layers in the central portion in the thickness direction when an excessive impact load is applied. Since it bends so as to tear in the thickness direction from the corresponding end portion between the third core yarn layers 13, the impact energy is efficiently absorbed. On the other hand, when the number of the core yarn layers 13 is an odd number, the center in the thickness direction of the three-dimensional braiding 11 is the core yarn layer 13 in the center in the thickness direction of the crash member 20 (when the core yarn layers 13 are five layers). Is the third layer) and the two core yarn layers 13 adjacent to the core yarn layer 13 in the center in the thickness direction (the second layer and the fourth layer when the core yarn layer 13 is five layers). It is. In this case, when the core yarn layer 13 at the center in the thickness direction is formed weaker than the other core yarn layers, the core yarn layer 13 at the center in the thickness direction and the core yarn layer 13 at the center in the thickness direction are adjacent to each other. Two places between the two core yarn layers 13 are easier to break than other portions, and the breakage proceeds at one or two places. Therefore, the odd number of the core yarn layers 13 stabilizes the breakage. Can be advanced.

The three-dimensional braiding 11 may have a configuration without penetrating yarns 14b structured so as to penetrate only the outermost layer or the innermost core yarn layer 13 and bend back.
○ When the number of the core yarn layers 13 of the three-dimensional braiding 11 is an odd number, the same strength yarn (fiber bundle) is used for all the penetrating yarns 14a and 14b, and the core yarn layer 13 at the center in the thickness direction is replaced with another core yarn layer 13 It may be formed weaker than the strength of the core yarn layer 13. For example, as shown in FIG. 4, the core yarn 12 constituting the core yarn layer 13 (third core yarn layer 13) at the center in the thickness direction is thinner than the core yarn 12 constituting the other core yarn layer 13. (Fiber bundle) is used. In this case, when an excessive impact load is applied to the crash member 20, the core yarn 12 of the central core yarn layer 13 is cut by the pulling force of the penetrating yarn 14 a that passes through the central core yarn layer 13 and turns back. Therefore, even if the number of the core yarn layers 13 is an odd number, the crush member 20 is formed from the end corresponding to the core yarn layer 13 at the center in the thickness direction of the crush member 20 when an excessive impact load is applied. It is bent so as to tear in the thickness direction, and is successively deformed and destroyed.

  A fiber bundle constituting the core yarn 12 and the penetrating yarns 14a and 14b is not limited to carbon fiber. For example, inorganic fibers such as glass fibers and ceramic fibers, or high-strength organic fibers such as aramid fibers, poly-p-phenylenebenzobisoxazole fibers, and ultrahigh molecular weight polyethylene fibers may be used. It is selected as appropriate. For example, when the required performance of rigidity and strength for the crash member 20 is high, carbon fiber is preferable. If an inexpensive glass fiber is used for the fiber material, the cost is low.

The yarn constituting the core yarn 12 and the penetrating yarns 14a and 14b is not limited to a non-twisted fiber bundle, and may be a yarn in which fibers are twisted.
○ The configuration in which the strength of the fiber bundle constituting the penetrating yarn 14a penetrating the core yarn 12 and the adjacent core yarn layer 13 is weaker than the other core yarns 12 and penetrating yarns 14a and 14b is limited to the method of thinning the fiber bundle. Alternatively, a method of changing the material and type (non-twisted yarn, twisted yarn, filament yarn, staple yarn) of the fiber bundle may be used.

  ○ As a configuration for making the strength to peel between the selected core yarn layers 13 weaker than the strength to peel between the other core yarn layers 13, the penetrating yarn that folds back through the selected adjacent core yarn layers 13 The number of 14a may be reduced. In this case, it is possible to reduce the weight and cost of the three-dimensional braiding 11 and thus the fiber-reinforced composite material by simply reducing the number of penetrating yarns 14a set in the three-dimensional braiding device when the three-dimensional braiding 11 is manufactured. .

  The configuration in which the number of penetrating yarns 14a that fold through the selected adjacent core yarn layers 13 is reduced is not limited to a configuration in which the same yarn is used as the core yarn 12 and the penetrating yarns 14a and 14b. For example, the penetration layer 14a of the selected layer is thin and has a small number, or the penetration layer 14a of the selected layer is a yarn made of a material having a lower strength than other yarns and has a small number. Good.

  The three-dimensional braiding 11 is the center in the thickness direction, that is, when the number of core yarn layers 13 is an even number, the portion of the penetrating thread 14a is weak, and when the number of core yarn layers 13 is an odd number, the center core yarn layer is It is not restricted to the structure in which 13 part is formed weakly. In the case of the three-dimensional braiding 11 having a large number of core yarn layers 13, a portion other than the center in the thickness direction may be weakly formed. However, when the crash member 20 receives an excessive impact load, the impact energy can be absorbed stably and stably when the successive deformation fracture proceeds from the end in a symmetrical state. It is preferable that the portion that does not come off is weakly formed.

  ○ The three-dimensional braiding 11 has the weakest peel strength between selected core yarn layers among the core yarn layers 13 provided in the middle of the thickness direction or in the middle between the outermost layer and the innermost layer, and the outermost layer is more than that. And you may form so that intensity | strength may increase gradually toward the innermost layer. When a fiber reinforced composite material using the three-dimensional braiding 11 as a reinforcing fiber is used as the crash member 20, when an excessive impact load is applied to the crash member 20 by appropriately setting a change in strength, the crash occurs. The member 20 can be successively and stably deformed and destroyed from its end.

  The three-dimensional braiding 11 is not limited to a cylindrical shape, and may be a cylindrical shape. For example, the cross-sectional area in a polygonal cylinder shape such as a square cylinder shape or a hexagonal cylinder shape or an elliptical cylinder shape, a cylindrical shape whose diameter changes in the axial direction (conical truncated cone shape), or a cross section perpendicular to the axial direction is from one end to the other. It may be a polygonal frustum shape that gradually becomes smaller toward.

  The thermosetting resin used as the matrix resin for the fiber reinforced composite material is not limited to an epoxy resin, and a thermosetting resin such as a vinyl ester resin, an unsaturated polyester resin, a phenol resin, or a polyimide resin may be used. The matrix resin is not limited to a thermosetting resin, and a thermoplastic resin such as polyamide, polybutylene terephthalate, polycarbonate, polyethylene, polypropylene, or ABS resin may be used. However, thermosetting resins are preferred because they are generally excellent in moldability and excellent in chemical resistance and weather resistance.

  When forming a fiber reinforced composite material using the three-dimensional braiding 11 as a reinforcing fiber, the resin may be impregnated and cured after changing the shape of the three-dimensional braiding 11.

  11 ... three-dimensional braiding, 12 ... core yarn, 13 ... core yarn layer, 14a, 14b ... penetrating yarn.

Claims (7)

A core yarn layer formed of a core yarn extending in the axial direction, and a three-dimensional braid formed in a cylindrical shape from a penetrating yarn organized so as to penetrate the core yarn layer,
The core yarn layer is provided with four or more layers, and the penetrating yarn is structured so as to be folded back through two adjacent core yarn layers, the outermost core yarn layer and the innermost core yarn. The strength of the selected core yarn layer of the core yarn layers provided between the layers or the strength of peeling between selected adjacent core yarn layers is weaker than the strength of peeling between other adjacent core yarn layers Three-dimensional braiding characterized by that.   2. The three-dimensional braiding according to claim 1, wherein the penetration yarn penetrating the selected core yarn layer is formed to be weaker than other penetration yarns.   The three-dimensional braiding according to claim 1 or 2, wherein the three-dimensional braiding is formed with a weak center in the thickness direction.   The core yarn and the penetrating yarn are all made of the same material, and the thickness of the core yarn constituting the selected core yarn layer or the penetrating yarn penetrating the selected adjacent core yarn layer is thin. The three-dimensional braiding according to any one of claims 1 to 3.   The number of penetrating yarns that fold back through the selected core yarn layer or the selected adjacent core yarn layers is smaller than penetrating yarns that fold back through other core yarn layers. 3. Three-dimensional braiding as described in 3.   A fiber-reinforced composite material comprising the three-dimensional braiding according to any one of claims 1 to 5 as a reinforcing fiber.   A three-dimensional braiding forming step for forming the three-dimensional braiding according to any one of claims 1 to 5 on the outside of the mandrel using the three-dimensional braiding device, and the formed three-dimensional braiding A method for producing a fiber-reinforced composite material, comprising: a mandrel removing step for removing the mandrel from the inside of the wrapping; and a resin impregnation curing step for impregnating and curing the resin in the three-dimensional braiding from which the mandrel has been removed. .

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