Fiber-reinforced resin material for vehicle body

Abstract

A fiber-reinforced resin material (M) for a vehicle body is provided with: a plurality of first reinforcing fiber layers (1) formed from unexpanded reinforcing fiber bundles; a second reinforcing fiber layer group (2) formed by continuously laminating a plurality of second reinforcing fiber layers (2a) formed by expanded reinforcing fiber bundles; and a matrix resin that is impregnated in the first reinforcing fiber layer (1) and the second reinforcing fiber layer (2a) and is reinforced by the first reinforcing fiber layer (1) and the second reinforcing fiber layer (2a). When a load is generated in the in-plane direction by an external force (F) that bends the fiber-reinforced resin material (M) and a compressive force or a tensile force acts on the fiber-reinforced resin material (M), the thickness center surface (CP) of the fiber-reinforced resin material (M) is smaller than the thickness center surface (CP) of the fiber-reinforced resin material (M). The region on the inner side of the bend is a compression-side region (CR) to which compressive stress acts, and the region on the outer side of the bend is a tensile-side region (TR) to which tensile stress acts. The second reinforcing fiber layer group (2) is disposed in the tension-side region (TR).

Description

Technical Field

[0001] The present invention relates to a fiber reinforced plastic member for a vehicle body. Background Art

[0002] The following Patent Document 1 discloses a carbon fiber reinforced plastic material. In the carbon fiber reinforced plastic material disclosed in Patent Document 1, a plurality of carbon fiber thin layers formed by tow spreading are laminated in its matrix resin. The fiber bundle of the carbon fiber for the carbon fiber reinforced plastic is composed of a very large number of single filaments and usually has a circular or elliptical cross section. The fiber bundle is also called a tow, and carbon fiber single filaments having a diameter of 4 to 7 μm are often used in the tow of the carbon fiber.

[0003] Tows are classified into 12k, 24k, etc. according to the number of their single filaments. A 12k tow is composed of 12,000 single filaments. Usually, a relatively thin tow of 24k or less is called a normal tow, and a thick tow of 40k or more is called a large tow. The tow spreading technology is a technology for spreading the single filaments of a tow thinly and uniformly, and usually a large tow is used. If a carbon fiber reinforced plastic material is formed by laminating a plurality of carbon fiber thin layers formed using the spread tow, the mechanical properties such as the strength and elastic modulus (hardness) of the carbon fiber reinforced plastic material can be improved as described in Patent Document 1.

[0004] Prior art documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2014-208457 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] However, since the thickness of one layer of the carbon fiber thin layer becomes thinner, the number of laminated carbon fiber thin layers in the carbon fiber reinforced plastic material increases. Therefore, there is a problem that the lamination man-hours increase and it is difficult to improve the productivity.

[0009] An object of the present invention is to provide a fiber reinforced plastic member for a vehicle body that can improve mechanical properties and at the same time improve productivity.

[0010] Means for Solving the Problems

[0011] The fiber-reinforced resin material for vehicle body according to the first feature of the present invention includes: a plurality of first reinforcing fiber layers formed of unopened reinforcing fiber bundles; a second reinforcing fiber layer group formed by continuously laminating a plurality of second reinforcing fiber layers formed of opened reinforcing fiber bundles; and a matrix resin that infiltrates into the first reinforcing fiber layers and the second reinforcing fiber layers and is reinforced by the first reinforcing fiber layers and the second reinforcing fiber layers. When a load, a compressive force, or a tensile force acts on the fiber-reinforced resin material in the in-plane direction due to an external force that bends the fiber-reinforced resin material, with respect to the central plane of the thickness of the fiber-reinforced resin material, the region on the inner side of the bend is set as the compression-side region where compressive stress acts, and the region on the outer side of the bend is set as the tension-side region where tensile stress acts. The second reinforcing fiber layer group is disposed in the tension-side region.

[0012] The fiber-reinforced resin material for vehicle body according to the second feature of the present invention includes: a plurality of first reinforcing fiber layers formed of unopened reinforcing fiber bundles; a second reinforcing fiber layer group formed by continuously laminating a plurality of second reinforcing fiber layers formed of opened reinforcing fiber bundles; and a matrix resin that infiltrates into the first reinforcing fiber layers and the second reinforcing fiber layers and is reinforced by the first reinforcing fiber layers and the second reinforcing fiber layers. When a load, a compressive force, or a tensile force acts on the fiber-reinforced resin material in the in-plane direction due to an external force that bends the fiber-reinforced resin material, with respect to the central plane of the thickness of the fiber-reinforced resin material, the region on the inner side of the bend is set as the compression-side region where compressive stress acts, and the region on the outer side of the bend is set as the tension-side region where tensile stress acts. The second reinforcing fiber layer group is disposed in the compression-side region.

[0013] Effects of the Invention

[0014] According to the above first feature, it is possible to reduce the number of laminations of the second reinforcing fiber layers that form a thin layer, thereby improving the productivity, and at the same time, the strength of the fiber-reinforced resin material is increased by the second reinforcing fiber layer group.

[0015] According to the above second feature, it is possible to reduce the number of laminations of the second reinforcing fiber layers that form a thin layer, thereby improving the productivity, and at the same time, the hardness of the fiber-reinforced resin material is increased by the second reinforcing fiber layer group. Description of the Drawings

[0016] Figure 1 is a schematic perspective view for explaining opening of fibers.

[0017] Figure 2 is a partial cross-sectional view of the fiber-reinforced resin material for explaining the tension / compression-side region.

[0018] Figure 3 is a schematic partial cross-sectional view of the fiber-reinforced resin material of the first embodiment.

[0019] Figure 4 is a schematic partial cross-sectional view of the fiber-reinforced resin material of the second embodiment.

[0020] Figure 5 is a schematic partial cross-sectional view of the fiber-reinforced resin material of the third embodiment. Detailed Embodiments

[0021] First, with reference to Figure 1 "fiber spreading" will be described. Fiber spreading is a technique related to the reinforcing fibers of long fibers and is not used for the reinforcing fibers of short fibers. The reinforcing fibers of unspread long fibers are in the state of a fiber bundle 11 in which many single filaments 10 are bundled as shown on the left, that is, a tow 11. The tow 11 includes several thousand to several tens of thousands of single filaments. In addition, Figure 1 this is a schematic diagram, and the number of single filaments 10 is not accurate. The cross-section of the unspread tow 11 is circular or elliptical. The technique of flattening and expanding it into a tow 12 as shown on the right is the fiber spreading technique, and there are various fiber spreading methods. The spread tow 12 can be arranged in parallel to form a unidirectional (UD) reinforcing fiber layer, or the spread tow 12 can be woven to form a quasi-isotropic reinforcing fiber layer. Quasi-isotropy can also be achieved by laminating multiple tows 12 with the directions of the unidirectional layers crossed. Figure 1 Figure 1 In addition, by observing the thickness of the reinforcing fiber layer and the uniformity of the distribution of the single filaments within the reinforcing fiber layer, it is possible to determine whether the reinforcing fiber layer in the formed fiber-reinforced resin material is formed from a spread fiber bundle (tow).

[0022] The thickness of the reinforcing fiber layer composed of the spread tow 12 becomes thinner. Therefore, the matrix resin can be sufficiently infiltrated into the reinforcing fiber layer. As a result, resin peeling within the reinforcing fiber layer can be suppressed. In addition, if tows 11 with a circular cross-section are arranged, gaps are likely to be formed, and by laminating flat tows 12, the fiber volume content Vf [%] of the reinforcing fibers can also be increased. As a result, the mechanical properties of the fiber-reinforced resin can be improved. Therefore, the fiber-reinforced resin using the spread tow 12 has improved mechanical properties. However, in the case of forming a fiber-reinforced resin material using only the spread tow 12, as described above, a larger number of laminations are required compared to the reinforcing fiber layer composed of the unspread tow 11.

[0023]

[0024] ​​There are various methods for forming a fiber-reinforced resin material, such as a method using prepreg and an RTM method using a thermoplastic resin. The prepreg uses a thermosetting resin. In the method using prepreg, a large number of laminations are required when laminating a thin prepreg using a spread fiber tow 12 on a shaping mold. In the RTM method, a large number of laminations are also required when laminating the spread fiber tow 12 in the mold. Therefore, the lamination process takes a lot of time and it is difficult to improve productivity. In the embodiment described below, by using both a reinforcing fiber layer using a spread fiber tow 12 and a reinforcing fiber layer using an unspread fiber tow 11, and optimizing the arrangement of the reinforcing fiber layer using the spread fiber tow 12 at the same time, the productivity is improved.

[0025] Next, before describing the following embodiments, refer to Figure 2 and explain the terms "tensile side region" and "compressive side region". In Figure 2 a general fiber-reinforced resin material 100 is shown. Due to the external force F that bends the fiber-reinforced resin material 100, a load is generated in the in-plane direction, and a compressive force or a tensile force acts on the fiber-reinforced resin material 100. In Figure 2 the example shown, the external force F acts in the thickness direction of the fiber-reinforced resin material 100, that is, in the lamination direction of the reinforcing fiber layer 101. In addition, Figure 2 also Figure 1 schematically shows a cross-section of the fiber-reinforced resin material 100 in the same way. In Figure 2 the reinforcing fibers themselves in each reinforcing fiber layer 101 are not explicitly shown, and a state where the matrix resin infiltrates into each reinforcing fiber layer 101 is shown. In addition, the matrix resins of the respective reinforcing fiber layers 101 do not actually form a clear boundary with each other, but are continuous with each other. For example, after laminating prepregs in which the matrix resin infiltrates the reinforcing fiber layer and then hardening the matrix resin by heating, after temporarily softening (liquefying) the matrix resin as a thermosetting resin, a hardening reaction occurs and it solidifies. During this process, there is no clear boundary between the matrix resins of the prepregs, and the matrix resins are integrated. Figure 1 and Figure 2 such schematic representations are the same in Figures 3 to 5 described later.

[0026] As Figure 2As shown, when a load is generated in the in-plane direction due to an external force F that bends the fiber-reinforced resin material 100 and a compressive force or a tensile force acts on the fiber-reinforced resin material 100, a compressive stress acts on the inner side of the bend (the bending concave side) inside the fiber-reinforced resin material 100, and a tensile stress acts on the outer side of the bend (the bending convex side). Here, with respect to the central plane CP of the thickness of the fiber-reinforced resin material 100, the region on the inner side of the bend of the fiber-reinforced resin material 100 is defined as the compressive-side region CR where the compressive stress acts. Similarly, the region on the outer side of the bend of the fiber-reinforced resin material 100 is defined as the tensile-side region TR where the tensile stress acts. Hereinafter, with reference to Figures 3 to 5 the first to third embodiments of the present invention will be described. The terms "tensile-side region TR" and "compressive-side region CR" are as defined herein.

[0027] As described below Figures 3 to 5 the fiber-reinforced resin material M of the first to third embodiments shown below is used for a vehicle body. As the fiber-reinforced resin material M for a vehicle body, examples thereof include a vehicle body frame structure material and a vehicle body panel. The vehicle body frame structure material is a member that bears a collision load during a vehicle collision. More specifically, as the vehicle body frame structure material, examples thereof include front / rear longitudinal beams, side beams, A / B / C pillars, roof longitudinal beams, and the like. In addition, as the vehicle body panel, more specifically, examples thereof include a hood / bonnet that covers the engine / motor room at the front of the vehicle body, a trunk lid / boot that covers the trunk room at the rear of the vehicle body, front / rear fenders, door panels, a vehicle body roof panel, and the like.

[0028] The vehicle body frame structure material is a member that bears a collision load during a vehicle collision. When the fiber-reinforced resin material M is a longitudinal beam, the longitudinal beam buckles during a front collision or a rear collision to absorb the collision energy. The buckling mode of the longitudinal beam is controlled by its stiffeners, reinforcing ribs formed in the longitudinal beam, and the like. That is, it is possible to know how the external force F that bends the fiber-reinforced resin material M acts on the fiber-reinforced resin material M based on the position in the longitudinal beam of the fiber-reinforced resin material M. Therefore, it is possible to know the "tensile-side region TR" and the "compressive-side region CR" of the fiber-reinforced resin material M when the external force F that bends the fiber-reinforced resin material M acts. When the fiber-reinforced resin material M is a side beam or a B-pillar, the side beam and the B-pillar ensure the passenger compartment, that is, the survival space, during a side collision. That is, it can be known that: if the external force F during a side collision is considered, the passenger compartment side of the fiber-reinforced resin material M becomes the "tensile-side region TR". When the fiber-reinforced resin material M is an A / C pillar or a roof longitudinal beam, the A / C pillar and the roof longitudinal beam ensure the passenger compartment, that is, the survival space, during a vehicle rollover. That is, it can be known that: if the external force F during a vehicle rollover is considered, the passenger compartment side of the fiber-reinforced resin material M becomes the "tensile-side region TR".

[0029] The body panel is mainly a member that forms the outer panel of the body. When the fiber-reinforced resin material M is the body panel, an external force F acts from the outside of the vehicle. There are also cases where luggage is placed on the hood / bonnet and the roof panel, and cases where a person leans on the fender and the door panel. Therefore, it can be known that when the fiber-reinforced resin material M is the body panel, the outer surface side of the body panel where the external force F acts becomes the "compression side region CR". If the body panel easily flexes, the quality perception is damaged.

[0030] As Figure 3 shown, the fiber-reinforced resin material M of the first embodiment includes a plurality of first reinforcing fiber layers 1, a second reinforcing fiber layer group 2 formed by continuously laminating a plurality of second reinforcing fiber layers 2a, and a matrix resin. Each first reinforcing fiber layer 1 is formed of an unopened reinforcing fiber bundle (tow). Each second reinforcing fiber layer 2a is formed of an opened reinforcing fiber bundle (tow). The matrix resin infiltrates into the first reinforcing fiber layer 1 and the second reinforcing fiber layer 2a and is reinforced by the first reinforcing fiber layer 1 and the second reinforcing fiber layer 2a.

[0031] The first reinforcing fiber layer 1 and the second reinforcing fiber layer 2a may each have a single directionality in which the tows are arranged in parallel, or may be woven to have quasi-isotropy. In addition, by laminating these fiber layers, quasi-isotropy can also be achieved by crossing the directionality of the angular layers. The reinforcing fiber of the present embodiment is a carbon fiber. The second reinforcing fiber layer group 2 is formed by continuously laminating the second reinforcing fiber layers 2a formed of opened tows. Therefore, as described above, the second reinforcing fiber layer group 2 has good mechanical properties.

[0032] The second reinforcing fiber layer group 2 is disposed in the tensile side region TR. The carbon fiber reinforced resin (CFRP) reinforced by the reinforcing fiber, especially the carbon fiber used in the present embodiment, can effectively resist the tensile force. Therefore, by disposing the second reinforcing fiber layer group 2 in the tensile side region TR, the bending strength of the fiber-reinforced resin material M can be increased. For example, strength is required for the above-described body frame structure material, and therefore, the fiber-reinforced resin material M of the present embodiment can be used as a body frame structure material.

[0033] The fiber-reinforced resin material M may also be formed only by a number of second reinforcing fiber layers 2a. However, as described above, it is difficult to improve the productivity as the number of layers increases. As in the present embodiment, by using the second reinforcing fiber layer group 2 only locally and the first reinforcing fiber layer 1 for the remaining part, it is possible to minimize the increase in the number of layers and improve the productivity, while increasing the strength of the fiber-reinforced resin material M by using the second reinforcing fiber layer group 2. In addition, since the second reinforcing fiber layer group 2 with a relatively high fiber volume fraction Vf of carbon fiber is used only locally, it is also possible to minimize the increase in the usage amount of expensive carbon fiber and suppress the increase in the production cost of the fiber-reinforced resin material M.

[0034] In particular, in the present embodiment, the second reinforcing fiber layer group 2 is used as the outermost layer in the tensile side region TR of the fiber-reinforced resin material M. Therefore, the second reinforcing fiber layer group 2 can most effectively increase the strength of the fiber-reinforced resin material M. Even if it is not the outermost layer, as long as the second reinforcing fiber layer group 2 is arranged in the tensile side region TR, the strength of the fiber-reinforced resin material M can be increased. However, by arranging the second reinforcing fiber layer group 2 in the outermost layer where the tensile stress generated due to the external force F is the largest within the fiber-reinforced resin material M, the bending strength of the fiber-reinforced resin material M can be most effectively increased.

[0035] In addition, it is also known that the bending strength is increased by the method of using the second reinforcing fiber layer group 2 only as the outermost layer in the tensile side region TR as in the present embodiment, compared with the case where the fiber-reinforced resin material M is formed only by a number of second reinforcing fiber layers 2a. The reason is that if the fiber-reinforced resin material M is formed only by a number of second reinforcing fiber layers 2a, delamination due to compressive failure is likely to occur in the second reinforcing fiber layer 2a in the compressive side region CR. In the case of only considering strength, when the second reinforcing fiber layer group 2 is arranged in the tensile side region TR, the strength of the fiber-reinforced resin material M can be increased by arranging only the first reinforcing fiber layer 1 in the compressive side region CR.

[0036] In addition, it is also known that as in the present embodiment, if a single second reinforcing fiber layer group 2 is arranged in the tensile side region TR and the remaining reinforcing fiber layers are the first reinforcing fiber layer 1, the deviation of the strength of the fiber-reinforced resin material M is less. Specifically, the CV (Coefficient of Variation) value of the strength of the fiber-reinforced resin material M can be suppressed to a lower level. In the case of only considering strength, when the second reinforcing fiber layer group 2 is arranged in the tensile side region TR, arranging the first reinforcing fiber layer 1 in the compressive side region CR can suppress the deviation of the strength of the fiber-reinforced resin material M.

[0037] In addition, in the present embodiment, only a single second reinforcing fiber layer group 2 is disposed in the stretching side region TR. In order to suppress the number of layers, it may be a single second reinforcing fiber layer group 2, but it does not prevent two or more second reinforcing fiber layer groups 2 from being disposed in the stretching side region TR. For example, the structure may be as follows. The second reinforcing fiber layer group 2 is disposed on the outermost layer of the stretching side region TR, and the first reinforcing fiber layer 1 is disposed on the inner side adjacent thereto. Then, the second reinforcing fiber layer group 2 is disposed further inside the first reinforcing fiber layer 1. The reinforcing fiber layer inside the second second reinforcing fiber layer group 2 and the remaining reinforcing fiber layers in the compression side region CR are the first reinforcing fiber layer 1.

[0038] In Figure 4 FIG. shows the fiber reinforced resin material M of the second embodiment. In the present embodiment, the second reinforcing fiber layer group 2 is disposed in the compression side region CR. Each first reinforcing fiber layer 1 of the present embodiment has the same structure as the first reinforcing fiber layer 1 of the first embodiment. Each second reinforcing fiber layer 2a of the present embodiment also has the same structure as the second reinforcing fiber layer 2a of the first embodiment. The second reinforcing fiber layer group 2 of the present embodiment also has the same structure as the second reinforcing fiber layer group 2 of the first embodiment. Therefore, the repeated description thereof is omitted.

[0039] By disposing the second reinforcing fiber layer group 2 in the compression side region CR, the elastic modulus of the fiber reinforced resin material M, that is, the hardness can be increased. For example, by using the fiber reinforced resin material M of the present embodiment for the above-described vehicle body panel, the deflection of the vehicle body panel can be effectively suppressed. In addition, the fiber reinforced resin material M of the present embodiment has a strength higher than that of the fiber reinforced resin material formed only of a plurality of first reinforcing fiber layers 1 (however, lower than the strength of the fiber reinforced resin material M of the first embodiment). It can be seen that in order to increase the elastic modulus (hardness) of the fiber reinforced resin material M, it is more effective to dispose the second reinforcing fiber layer group 2 only in the compression side region CR than to dispose the second reinforcing fiber layer group 2 only in the stretching side region TR.

[0040] As described above, if the fiber reinforced resin material M is formed of many second reinforcing fiber layers 2a, the number of layers increases and it is difficult to improve the productivity. As in the present embodiment, by using the second reinforcing fiber layer group 2 only locally and using the first reinforcing fiber layer 1 for the remaining part, the increase in the number of layers can be minimized to improve the productivity, and at the same time, the elastic modulus (hardness) of the fiber reinforced resin material M can be increased by using the second reinforcing fiber layer group 2. In addition, since the second reinforcing fiber layer group 2 having a high fiber volume fraction Vf of carbon fiber is used only locally, the increase in the use amount of expensive carbon fiber can also be minimized to suppress the increase in the production cost of the fiber reinforced resin material M.

[0041] In particular, in the present embodiment, the second reinforcing fiber layer group 2 serves as the outermost layer in the compression side region CR of the fiber reinforced resin material M. Therefore, the second reinforcing fiber layer group 2 can most effectively increase the elastic modulus (hardness) of the fiber reinforced resin material M. Even if it is not the outermost layer, as long as the second reinforcing fiber layer group 2 is arranged in the tensile side region TR, the elastic modulus (hardness) of the fiber reinforced resin material M can be increased. However, by arranging the second reinforcing fiber layer group 2 in the outermost layer, the flexural hardness of the fiber reinforced resin material M can be most effectively increased.

[0042] In addition, in the present embodiment, only a single second reinforcing fiber layer group 2 is arranged in the compression side region CR. In order to suppress the number of layers, it can be a single second reinforcing fiber layer group 2, but it does not prevent arranging two or more second reinforcing fiber layer groups 2 in the compression side region CR. For example, the structure can be as follows. The second reinforcing fiber layer group 2 is arranged in the outermost layer of the compression side region CR, and the first reinforcing fiber layer 1 is arranged in the adjacent inner side thereof. Then, the second reinforcing fiber layer group 2 is arranged in the more inner side of the first reinforcing fiber layer 1. The reinforcing fiber layer on the inner side of the second second reinforcing fiber layer group 2 and the remaining reinforcing fiber layers in the tensile side region TR are set as the first reinforcing fiber layer 1.

[0043] In Figure 5 shows the fiber reinforced resin material M of the third embodiment. In the present embodiment, the second reinforcing fiber layer groups 2 are respectively arranged in the tensile side region TR and the compression side region CR. If the structure is like this, the flexural elastic modulus (hardness) of the fiber reinforced resin material M can be increased compared with the case where the second reinforcing fiber layer group 2 is only arranged in the compression side region CR like the second embodiment. However, the flexural strength of the fiber reinforced resin material M is worse than that in the first embodiment where the second reinforcing fiber layer group 2 is only arranged in the tensile side region TR, and is increased compared with the case where the second reinforcing fiber layer group 2 is only arranged in the compression side region CR like the second embodiment. The reason why the flexural strength of the fiber reinforced resin material M in the present embodiment is lower than that in the first embodiment is that layer peeling caused by compression failure is likely to occur at the second reinforcing fiber layer 2a of the second reinforcing fiber layer group 2 in the compression side region CR.

[0044] Therefore, there are cases where the arrangement of the second reinforcing fiber layer group 2 like the present embodiment is effective according to the mechanical properties (strength and elastic modulus) required for the position in the vehicle body using the fiber reinforced resin material M. In addition, in the present embodiment, the second reinforcing fiber layer groups 2 are respectively arranged in the tensile side region TR and the compression side region CR, but in addition to these two second reinforcing fiber layer groups 2, it does not prevent further arranging the second reinforcing fiber layer group 2.

[0045] In particular, in the present embodiment, the second reinforcing fiber layer group 2 serves as the outermost layer in the tensile side region TR of the fiber reinforced resin material M and also serves as the outermost layer in the compressive side region CR of the fiber reinforced resin material M. Therefore, the second reinforcing fiber layer group 2 can most effectively increase the elastic modulus (hardness) of the fiber reinforced resin material M, and can also increase the strength to a certain extent, and can improve the mechanical strength balance of the fiber reinforced resin material M well.

[0046] In the above-described first to third embodiments, the layer thickness of the second reinforcing fiber layer 2a is preferably 80 μm or more and 300 μm or less. The second reinforcing fiber layer 2a formed using a spread fiber tow brings about the improvement of the above-described mechanical properties by making the monofilaments thinner. If the thickness is less than 80 μm, the thickness of the spread fiber tow is too thin and the straightness of the tow decreases, and gaps are likely to be generated between the reinforcing fibers during lamination. If gaps are likely to be generated, it is difficult to obtain the effect of improving the mechanical properties due to the increase in the fiber volume fraction Vf. In addition, if the thickness is less than 80 μm, the number of laminations of the second reinforcing fiber layer 2a increases, and thus it is difficult to obtain the effect of improving productivity. On the other hand, if the thickness is greater than 300 μm, it is difficult to obtain the above-described effect due to the thinning of the "spread fiber" into a thin layer.

[0047] In the above-described first to third embodiments, the reinforcing fiber of the second reinforcing fiber layer 2a is preferably a carbon fiber. Since carbon fiber is also lightweight among the reinforcing fibers, it can effectively contribute to the weight reduction of the vehicle body. In addition, carbon fiber also has excellent fatigue resistance, chemical resistance, and corrosion resistance among the reinforcing fibers, and is convenient for use in the vehicle body. Moreover, carbon fiber is also excellent in terms of strength and is also easy to apply to the spread fiber technology.

[0048] The present invention is not limited to the above-described embodiments. For example, in Figure 2 it is illustrated that an external force F that bends the fiber reinforced resin material 100 acts in the thickness direction of the fiber reinforced resin material 100, that is, in the lamination direction of the reinforcing fiber layer 101. However, the direction of the external force F that bends the fiber reinforced resin material M is not limited to the thickness direction or the lamination direction. There are also cases where the fiber reinforced resin material M bends due to an external force F from a direction other than the thickness direction and the lamination direction. In such a case, the "tensile side region TR" and the "compressive side region CR" can be defined as long as the bending shape (bending inner / outer side) of the fiber reinforced resin material M is considered.

[0049] In addition, in the above-described embodiment, the reinforcing fibers of the first reinforcing fiber layer 1 and the second reinforcing fiber layer 2a are carbon fibers. As described above, the reinforcing fibers of the second reinforcing fiber layer 2a are preferably carbon fibers, but the reinforcing fibers of the first reinforcing fiber layer 1 and the second reinforcing fiber layer 2a are not limited to carbon fibers. Other reinforcing fibers such as glass fibers, aramid fibers, boron fibers, Kevlar fibers, and natural fibers can also be used. In addition, the type of matrix resin of the fiber reinforced resin material M is not limited. For example, as described above, it can be either a thermosetting resin or a thermoplastic resin. Moreover, the forming method of the fiber reinforced resin material M is not limited, and various forming methods using long fiber reinforcing fibers such as autoclave forming and RTM forming using prepregs can be used.

[0050] Explanation of reference numerals

[0051] M, fiber reinforced resin material; 1, first reinforcing fiber layer; 2a, second reinforcing fiber layer; 2, second reinforcing fiber layer group; CP, (central plane in the thickness direction of the fiber reinforced resin material M); TR, tensile side region; CR, compression side region; F, external force.

Claims

1. A fiber-reinforced resin material, which is a fiber-reinforced resin material for a vehicle body, wherein, the fiber-reinforced resin material includes: a plurality of first reinforcing fiber layers formed of unopened reinforcing fiber bundles; a second reinforcing fiber layer group formed by continuously laminating a plurality of second reinforcing fiber layers formed of opened reinforcing fiber bundles; and a matrix resin that infiltrates into the plurality of first reinforcing fiber layers and the plurality of second reinforcing fiber layers and is reinforced by the plurality of first reinforcing fiber layers and the plurality of second reinforcing fiber layers. When a load, a compressive force, or a tensile force acts on the fiber-reinforced resin material in the in-plane direction due to an external force that bends the fiber-reinforced resin material, in the case where the region on the inner side of the bend of the fiber-reinforced resin material with respect to the central plane of the thickness of the fiber-reinforced resin material is set as a compression-side region where compressive stress acts and the region on the outer side of the bend of the fiber-reinforced resin material is set as a tension-side region where tensile stress acts, the second reinforcing fiber layer group is disposed in the tension-side region.

2. The fiber-reinforced resin material according to claim 1, wherein, the second reinforcing fiber layer group is also disposed in the compression-side region.

3. A fiber-reinforced resin material, which is a fiber-reinforced resin material for a vehicle body, wherein, the fiber-reinforced resin material includes: a plurality of first reinforcing fiber layers formed of unopened reinforcing fiber bundles; a second reinforcing fiber layer group formed by continuously laminating a plurality of second reinforcing fiber layers formed of opened reinforcing fiber bundles; and a matrix resin that infiltrates into the plurality of first reinforcing fiber layers and the plurality of second reinforcing fiber layers and is reinforced by the plurality of first reinforcing fiber layers and the plurality of second reinforcing fiber layers. When a load, a compressive force, or a tensile force acts on the fiber-reinforced resin material in the in-plane direction due to an external force that bends the fiber-reinforced resin material, in the case where the region on the inner side of the bend of the fiber-reinforced resin material with respect to the central plane of the thickness of the fiber-reinforced resin material is set as a compression-side region where compressive stress acts and the region on the outer side of the bend of the fiber-reinforced resin material is set as a tension-side region where tensile stress acts, the second reinforcing fiber layer group is disposed in the compression-side region.

4. The fiber-reinforced resin material according to any one of claims 1 to 3, wherein, the second reinforcing fiber layer group is the outermost layer of the fiber-reinforced resin material.

5. The fiber-reinforced resin material according to any one of claims 1 to 4, wherein, the thickness of each layer of the plurality of second reinforcing fiber layers is 80 μm or more and 300 μm or less.

6. The fiber-reinforced resin material according to any one of claims 1 to 5, wherein, the reinforcing fiber of the reinforcing fiber bundle for the plurality of second reinforcing fiber layers is a carbon fiber.

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