FIBER REINFORCED PLASTIC MEMBER

Abstract

Provided is a fiber reinforced plastic member made by a braiding technique to obtain high rigidity and superior vibration damping performance under a bending load. A reinforcing member made of carbon fiber reinforced plastic resin extends in a specific direction along an axis of the reinforcing member and includes a carbon fiber braided structure. The carbon fiber braided structure has a structure in which a plurality of axial yarns, a plurality of first braid yarns, and a plurality of second braid yarns are braided. A plurality of first braid yarns are wound to intersect the axis at a first braid angle. A plurality of second braid yarns are wound to intersect the axis at a second braid angle. The first braid yarns and the second braid yarns intersect each other. The reinforcing member has a region approximately in the longitudinal middle where the first braid angle and the second braid angle of the first braid yarns and the second braid yarns take values larger than in other region regarding the longitudinal direction.

Description

TECHNICAL FIELD

The present invention relates to a fiber reinforced plastic member, more particularly, a fiber reinforced plastic member made by a braiding technique.

BACKGROUND ART

Carbon fiber reinforced plastic members are used for structural members for automobiles, aircrafts, and industrial machines (JP 2017-61170 A, JP 2015-160551 A).

JP 2017-61170 A discloses a structure using a carbon fiber reinforced plastic strip member to increase rigidity of a bottom of a vehicle body of an automobile. When the vehicle body deforms, the structure disclosed in JP 2017-61170 A applies a twist moment to the strip member.

JP 2015-160551 A discloses a carbon fiber reinforced plastic shaft used as a steering shaft of an automobile. The shaft disclosed in JP 2015-160551 A includes a carbon fiber reinforced plastic made by a braiding technique to braid carbon fibers oriented at predetermined braid angles.

As disclosed in the documents, light weight and high rigidity can be achieved using a carbon fiber reinforced plastic material.

Conventional techniques, such as that disclosed in JP 2015-160551 A, however, cannot achieve both high rigidity and superior damping performance. Using the technique disclosed in JP 2015-160551 A, high rigidity can be achieved using a carbon fiber reinforced plastic member made by the braiding technique. But a structural member made by the technique cannot obtain high damping performance.

For example, in a case of using a carbon fiber reinforced plastic member made by the braiding technique as a reinforcing member for a vehicle body of an automobile, the fiber reinforced plastic member including carbon fibers oriented to extend parallel to the vehicle width direction in the entire longitudinal region of the fiber reinforced plastic member obtains poor damping performance under a bending load.

Meanwhile, it is difficult for the fiber reinforced plastic member including carbon fibers oriented to extend diagonal to the vehicle width direction in the entire longitudinal region to obtain high rigidity under a bending load.

Such a problem also exists in other structures other than vehicle bodies of automobiles.

An object of the present invention is to provide a fiber reinforced plastic member that is made by a braiding technique and obtains high rigidity and superior vibration damping performance under a bending load.

SUMMARY OF INVENTION

A fiber reinforced plastic member according to an embodiment is made of fiber reinforced plastic resin and extends in a specific direction. The fiber reinforced plastic member comprises a fiber-braided structure. The fiber-braided structure includes first braid yarns wound to intersect a specific direction at a first braid angle, and second braid yarns wound to intersect the specific direction at a second braid angle, the first braid yarns and the second braid yarns being braided together. The fiber-braided structure includes a predetermined region between both ends, regarding a longitudinal direction of the fiber reinforced plastic member. At least one of the first braid angle and the second braid angle in the predetermined region is larger than the braid angle in an other region other than the predetermined region.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic bottom view illustrating a configuration of a bottom of a vehicle body using a fiber reinforced plastic member according to an embodiment of the present invention;

FIG. 2 is a schematic bottom view illustrating a configuration of a portion of the bottom of the vehicle body;

FIG. 3 is a schematic perspective view illustrating a configuration of a vehicle interior of the vehicle body;

FIG. 4 is a schematic perspective view illustrating a configuration of a reinforcing member;

FIG. 5 is a schematic view illustrating a configuration of a carbon fiber braided structure of a portion A, in FIG. 4, of the reinforcing member;

FIG. 6 is a schematic view of a carbon fiber braided structure of a portion B, in FIG. 4, of the reinforcing member;

FIG. 7 is a schematic perspective view illustrating a method for manufacturing a carbon fiber braided structure;

FIG. 8A is a cross-sectional view illustrating a cross-section of the portion A, in FIG. 4, of the reinforcing member;

FIG. 8B is a cross-sectional view illustrating a cross-section of the portion B, in FIG. 4, of the reinforcing member;

FIG. 9 is a performance chart illustrating a threshold line for evaluating an effect obtained by a high damping portion of the reinforcing member;

FIG. 10A is a performance chart where a braid angle θ₁ is 15 degrees and L₃/L₁ is 0.01;

FIG. 10B is a performance chart where the braid angle θ₁ is 15 degrees and L₃/L₁ is 0.004;

FIG. 10C is a performance chart where the braid angle θ₁ is 15 degrees and L₃/L₁ is 0.002;

FIG. 10D is a performance chart where the braid angle θ₁ is 15 degrees and L₃/L₁ is 0.001;

FIG. 11A is a performance chart where the braid angle θ₁ is 30 degrees and L₃/L₁ is 0.01;

FIG. 11B is a performance chart where the braid angle θ₁ is 30 degrees and L₃/L₁ is 0.004;

FIG. 11C is a performance chart where the braid angle θ₁ is 30 degrees and L₃/L₁ is 0.002;

FIG. 11D is a performance chart where the braid angle θ₁ is 30 degrees and L₃/L₁ is 0.001;

FIG. 12 is a performance chart where the braid angle θ₁ is 45 degrees and L₃/L₁ is 0.001; and

FIG. 13 is a schematic view illustrating a configuration of a carbon fiber braided structure of a longitudinal middle of a reinforcing member according to an exemplary modification of the present invention.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present invention will be described with reference to the drawings. It should be noted that the embodiment described below is an example of the present invention. The embodiment is disclosed by means of illustration and not by means of limitation except for an essential configuration of the present invention.

In FIGS. 1 to 3 used for the description below, “Fr”, “Re”, “Le”, and “Ri” respectively indicate the front side, the rear side, the left side, and the right side of the vehicle body. These are directions determined with reference to the moving direction of a vehicle as a product.

Embodiment

• 1. Bottom and Vehicle Interior of Vehicle Body 1

A bottom and a vehicle interior 1b of a vehicle body 1 according to an embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a schematic bottom view illustrating the bottom of the vehicle body 1. FIG. 2 is a schematic bottom view illustrating a configuration of a portion of the bottom of the vehicle body 1. FIG. 3 is a schematic perspective view illustrating a configuration of the vehicle interior 1b of the vehicle body 1.

The vehicle body 1 of the vehicle according to the embodiment is a monocoque vehicle body. As illustrated in FIGS. 1 to 3, the vehicle body 1 includes a floor panel 2 constituting a bottom (bottom face) of the vehicle interior 1b, a dash panel 3 partitioning an engine room 1a from the vehicle interior 1b, a pair of right and left front side frames 4 extending forward from the dash panel 3, and a pair of right and left rear side frames 5 extending rearward from the rear end portion of the floor panel 2.

The dash panel 3 extends upward from the front end portion of the floor panel 2.

The vehicle body 1 also includes a pair of right and left side sills 6 provided at right and left end portions of the floor panel 2, a pair of right and left hinge pillars 7 extending upward from the front end portions of a pair of the side sills 6, a pair of right and left center pillars 8 extending upward from the middle portions of a pair of the side sills 6, a pair of right and left front pillars 9 extending diagonally rearward from the top end portions of a pair of the hinge pillars 7, and a pair of right and left roof side rails 10 extending rearward from the rear end portions of a pair of the front pillars 9.

A pair of the roof side rails 10 are joined to the rear end portions of the upper end portions of the center pillars 8.

As illustrated in FIGS. 1 to 3, the floor panel 2 of the vehicle body 1 includes a tunnel 11 that has an approximately square shape in a bottom plan view. The tunnel 11 is provided in the middle portion regarding the vehicle width direction (Le-Ri direction), extends along the front-and-rear direction (Fr-Re direction), and protrudes into the vehicle interior 1b.

A pair of right and left tunnel frames 12 each extending in the front-and-rear direction (Fr-Re direction) are provided at right and left end portions of the tunnel 11. A pair of the tunnel frames 12 each has an approximately hat-shaped cross-section. The tunnel frames 12 each extend approximately parallel to the front-and-rear direction (Fr-Re direction) and forms together with the bottom of the floor panel 2 an approximately square closed cross-section.

A floor frame 13 extending in the front-and-rear direction (Fr-Re direction) and having an approximately hat-shaped cross-section is provided in a space between one of the side sills 6 and one of the tunnel frames 12 and in a space between the other side still 6 and the other tunnel frame 12. Each of the floor frames 13 is shaped such that a portion of the floor frame 13 further in the rear side (Re side) of the vehicle body 1 is closer to the outside of the vehicle body 1. The floor frame 13 extends approximately parallel to the front-and-rear direction (Fr-Re direction) and forms together with the floor panel 2 an approximately square closed cross-section.

The front end portion of each of the floor frames 13 is joined to the rear end portion of the front side frame 4.

The floor panel 2 includes cross members 14 and 15 provided in both sides of the tunnel 11 in the vehicle interior 1b and extending in the right-and left-direction (Le-Ri direction). Each of the cross members 14 and 15 has an approximately hat-shaped cross-section. Each of the cross members 14 and 15 extends in the right-and-left direction (Le-Ri direction) from the side wall of the tunnel 11 to the side wall of the side sill 6 and forms together with the top of the floor panel 2 an approximately square cross-section.

The cross member 14 is disposed in the middle regarding the direction from the hinge pillar 7 to the center pillar 8. The rear end portion of an upper frame 16 is joined to the front wall of the cross member 14. The rear end portion of the upper frame 16 is joined to the floor panel 2. In the opposite side of the joint, the front end portion of the floor frame 13 is joined to the floor panel 2.

The cross member 15 is disposed at a location corresponding to the center pillar 8 to be approximately parallel to the cross member 14.

A pair of right and left front seats (not shown) are provided in the vehicle interior 1b. Each seat includes a seat frame that gives strength and rigidity to the seat. Each seat is movable along a pair of right and left seat rails 17.

As illustrated in FIG. 3, one of the seat rails 17 is provided in the outer side regarding the vehicle width direction. This seat rail 17 has a front end portion (a front seat mount) fixed to the outer portion, regarding the vehicle width direction of the cross member 14 and a rear end portion (a rear seat mount) fixed to the outer portion, regarding the vehicle width direction of the cross member 15.

The other one of the seat rails 17 is provided in the inner side regarding the vehicle width direction. This seat rail 17 has a front end portion (a front seat mount) fixed to the inner portion, regarding the vehicle width direction of the cross member 14 and a rear end portion (a rear seat mount) fixed to the inner portion, regarding the vehicle width direction of the cross member 15.

A plurality of reinforcing members 21 to 27 are disposed under the floor panel 2.

• 2. Configuration of Reinforcing Members 21 to 27 and Structure for Mounting Reinforcing Members 21 to 27 to Vehicle Body 1

A configuration of reinforcing members 21 to 27 and a structure of mounting the reinforcing members 21 to 27 to the vehicle body 1 will be described using FIGS. 2 and 4. FIG. 4 is a schematic perspective view illustrating the configuration of the reinforcing member 21 (as an example of the reinforcing members 21 to 27).

As illustrated in FIG. 2, the vehicle body 1 according to an embodiment includes a plurality of the reinforcing members 21 to 27 disposed in a bilaterally symmetric arrangement. The reinforcing member 21 extends between the right side sill 6 and the right tunnel frame 12 of the vehicle body 1 and is fixed to the right side sill 6 and the right tunnel frame 12 at fix points P.

The reinforcing member 22 extends between the right and left tunnel frames 12 across the tunnel 11 and is fixed to the right and left tunnel frames 12 at fix points P. The reinforcing member 23 extends between the left side sill 6 and the left tunnel frame 12 of the vehicle body 1 and is fixed to the left side sill 6 and the tunnel frame 12 at fix points P.

The reinforcing member 24 is disposed further in the front side of the vehicle body 1 than the reinforcing member 23, extends between the left side sill 6 and the left tunnel frame 12 of the vehicle body 1, and is fixed to the left side sill 6 and the tunnel frame 12 at fix points P. The reinforcing member 25 extends between the right and left tunnel frames 12 across the tunnel 11 and is fixed to the right and left tunnel frames 12 at fix points P.

The reinforcing member 26 is disposed further in the rear side of the vehicle body 1 than the reinforcing member 25, extends between the right and left tunnel frames 12 across the tunnel 11, and is fixed to the right and left tunnel frames 12 at fix points P. The reinforcing member 27 interconnects the rear end of the reinforcing member 26 and an end of the reinforcing member 22 as well as an end of the reinforcing member 21, and is fixed to the tunnel frame 12 at fix points P.

As illustrated in FIG. 4, the reinforcing member 21 is a long cylinder-shaped or bar-shaped member extending in a predetermined specific direction. Specifically, the reinforcing member 21 includes a long cylindrical portion 21a extending in a predetermined specific direction, and fix-portions 21b and 21c provided at the ends of the long cylindrical portion 21a. Holes 21d and 21e allowing a bolt to be inserted (see arrows C and D) therein are respectively provided in the fix-portions 21b and 21c. The fix-portions 21b and 21c of the reinforcing member 21 are fixed to portions of the vehicle body 1 by bolts.

Although not illustrated in FIG. 4, the reinforcing members 22 to 27 have the same configuration as the reinforcing member 21. However, the length of the long cylindrical portion 21a is suitably determined according to the place where the long cylindrical portion 21a is used for the vehicle body 1.

The long cylindrical portions 21a of the reinforcing members 21 to 27 according to the embodiment include carbon fiber reinforced plastic resin (CFRP). Specifically, the long cylindrical portion 21a includes a carbon fiber reinforced plastic resin including a carbon fiber braided structure and a plastic resin part made by a braiding technique. The detail will be described later.

The reinforcing member 21 according to the embodiment includes the long cylindrical portion 21a having a length of L₁. A portion of the long cylindrical portion 21a which is at a distance L₂ from the end of the long cylindrical portion 21a, namely, the longitudinal middle and the peripheral region thereof of the long cylindrical portion 21a (the region indicated by an arrow B), has a low modulus and obtains high vibration damping performance.

Meanwhile, the reinforcing member 21 has a high-modulus region not including the region indicated by the arrow B (for example, the region indicated by an arrow A). The high-modulus region obtains high rigidity when the reinforcing member 21 is subjected to a bending load.

• 3. Carbon Fiber Braided Structure 210

A carbon fiber braided structure 210 of the reinforcing members 21 to 27 will be described using FIGS. 5 and 6. FIG. 5 is a schematic view of a portion A, in FIG. 4, of the carbon fiber braided structure 210 of the long cylindrical portion 21a of the reinforcing members 21 to 27. FIG. 6 is a schematic view of a portion B, in FIG. 4, of the carbon fiber braided structure 210 of the long cylindrical portion 21a of the reinforcing members 21 to 27.

As illustrated in FIG. 5, the carbon fiber braided structure 210 includes a plurality of axial yarns 211, a plurality of braid yarns 212, and a plurality of braid yarns 213, the yarns 211, 212, and 213 being braided together. The group of the braid yarns 212 or the group of the braid yarns 213 according to the embodiment is the group of first braid yarns and the other group is the group of second braid yarns.

As illustrated in FIG. 5, each of the axial yarns 211 is disposed approximately parallel to an axis Ax₂₁₀ of the carbon fiber braided structure 210. That is, each of the axial yarns 211 is disposed approximately parallel to the extending direction of the long cylindrical portion 21a. The adjacent axial yarns 211 are spaced apart from each other in the circumferential direction.

Meanwhile, each of the braid yarns 212 is wound around the axis Ax₂₁₀ at a braid angle of θ₁. The adjacent braid yarns 212 are also spaced apart from each other in the circumferential direction.

Each of the braid yarns 213 is wound around the axis Ax₂₁₀ at a braid angle of θ₁ and intersects the braid yarns 212. The adjacent braid yarns 213 are also spaced apart from each other in the circumferential direction.

For example, the braid angle θ₁ is 15 degrees or larger up to 45 degrees.

As illustrated in FIG. 6, in a region Ar₁ which is in an approximately middle portion of the long cylindrical portion 21a, the braid angle of the braid yarns 212 is θ₂ and the braid angle of the braid yarns 213 is also θ₂. That is, both the first braid angle and second braid angle are θ₂ in the embodiment.

For example, the braid angle θ₂ is 60 degrees or larger but smaller than 90 degrees.

As illustrated in FIG. 6, the region Ar₁ of the carbon fiber braided structure 210 according to the embodiment is centered on a longitudinal center C_L of the long cylindrical portion 21a and has a width L₃. For example, the length L₃ is determined by a ratio of L₃ to the length L₁ of the long cylindrical portion 21a, where the ratio takes a value of 0.001 or larger up to 0.01.

• 4. Method for Manufacturing Carbon Fiber Braided Structure 210

As described above, the carbon fiber braided structure 210 according to the embodiment has the braid angle in the middle region Ar₁ larger than the braid angle in the other region (for example, the region indicated by the arrow A in FIG. 4). A method for manufacturing the carbon fiber braided structure 210 having such a configuration will be described using FIG. 7. FIG. 7 is a schematic perspective view illustrating a configuration of a portion of a manufacturing apparatus used for manufacturing the carbon fiber braided structure 210.

As illustrated in FIG. 7, a braiding apparatus 500 is used for manufacturing the carbon fiber braided structure 210. The braiding apparatus 500 includes a plurality of bobbins 501, a track 502, and carriers 503. A plurality of the bobbins 501 feed carbon fibers (axial yarns 211 and braid yarns 212 and 213) while revolving, keeping the relative positional relationship between each other. The carbon fibers are wound around the circumferential face of a column-shaped mandrel M simply illustrated in the drawing.

The mandrel M and the elements disposed around the mandrel M, such as the bobbins 501, move relative to each other along the longitudinal direction of the mandrel M (that is, a linear relative movement) at a relative speed of V1. In the embodiment, the relative moving speed V1 is reduced only in a period when the braid yarns 212 and 213 are wound around a portion corresponding to the region Ar₁ of the carbon fiber braided structure 210. Alternatively, the revolving speed and the rotational speed of the bobbins 501 are increased only in a period when the braid yarns 212 and 213 are wound around a portion corresponding to the region Ar₁ of the carbon fiber braided structure 210.

• 5. Inner Diameters D₁ and D₂ and Outer Diameters D₃ and D₄ of Long Cylindrical Member 21a

Inner diameters D₁ and D₂ and outer diameters D₃ and D₄ of the long cylindrical portion 21a will be described using FIG. 8. FIG. 8A illustrates a cross-sectional view of the portion A, illustrated in FIG. 4, of the reinforcing member 21. FIG. 8B illustrates a cross-sectional view of the portion B, illustrated in FIG. 4, of the reinforcing member 21.

As illustrated in FIG. 8A, the long cylindrical portion 21a has the inner diameter D₁ and the outer diameter D₃ in the portion A in FIG. 4.

As illustrated in FIG. 8B, the long cylindrical portion 21a has the inner diameter D₂ and the outer diameter D₄ in the portion B (region Ar₁ in FIG. 4. The relationship between the inner diameters D₁ and D₂ and the outer diameters D₃ and D₄ of the long cylindrical portion 21a according to the embodiment is expressed below.

D₁>D₂   Formula 1

D₃=D₄   Formula 2

The relationship expressed by Formula 1 is due to the relationship between the braid angle θ₁ and the braid angle θ₂ of the braid yarns 212 and 213. As described above, the relationship θ₂>θ₁ means that the braid yarn 212 and the braid yarn 213 overlap each other by a longer circumferential length in the region where the braid angle is θ₂. By the manufacturing method described above, the mandrel is removed from the braided material and the braided material is heat-treated, resulting in shrinking of the inner circumferential face in the region Ar₁ along the radial direction. Formula 1 is thus satisfied.

• 6. Determination of Length L₃ and Braid Angle θ₂ in Region Ar₁

Determining the length L₃ and the braid angle θ₂ for the region Ar₁ will be described using FIGS. 9 to 12. FIG. 9 is a performance chart illustrating a threshold line of an area where the region Ar₁ of the reinforcing members 21 to 27 effectively works as a high damping portion. FIGS. 10A to 10D are performance charts where the braid angle θ₁ is 15 degrees. FIG. 10A shows the case where L₃/L₁=0.01. FIG. 10B shows the case where L₃/L₁=0.004. FIG. 10C shows the case where L₃/L₁=0.002. FIG. 10D shows the case where L₃/L₁=0.001. FIGS. 11A to 11D are performance charts where the braid angle θ₁ is 30 degrees. FIG. 11A shows the case where L₃/L₁=0.01. FIG. 11B shows the case where L₃/L₁=0.004. FIG. 11C shows the case where L₃/L₁=0.002. FIG. 11D shows the case where L₃/L₁=0.001. FIG. 12 is a performance chart where a braid angle θ₁ is 45 degrees and L₃/L₁ is 0.001.

• (1) Determining Threshold Line

As illustrated in FIG. 9, the performance chart has the horizontal axis indicating rigidity of the long cylindrical portion 21a and the vertical axis indicating damping performance. Absolute values indicated by the horizontal axis and the vertical axis depends on the shape and material of test pieces.

The solid line in FIG. 9 is a performance line of a case where a long cylindrical portion is formed by winding braid yarns at a uniform braid angle.

A threshold line for the embodiment is indicated by a broken line in FIG. 9. This line represents a configuration assumed to obtain a damping performance raised by 50% and the same level of rigidity compared to a configuration in which braid yarns are wound at a uniform braid angle. In the embodiment, the length L₃ and the braid angle θ₂ for the region Ar₁ are determined so as a point determining damping performance and rigidity to be in the upper right area of the threshold line in the chart illustrated in FIG. 9.

In FIG. 9, a broken line extending along the horizontal axis to indicate a damping performance of 0.00125 is the lower limit value of the damping ratio.

• (2) Case for θ₁=15 Degrees

FIGS. 10A to 10D are charts illustrating the relationship between rigidity and damping ratio where the braid angle θ₁ of the braid yarns 212 and 213 in the portion A in FIG. 4 is 15 degrees.

Under the condition of L₃/L₁=0.01 as illustrated in FIG. 10A, the damping ratio takes the lower limit value when θ₂ is 60 degrees. It can be understood that the condition of θ₁=15 degrees with θ₂=60 degrees improves the damping performance by 50%.

Under the condition of L₃/L₁=0.004 as illustrated in FIG. 10B, the damping ratio takes the lower limit value when θ₂ is 83.5 degrees. It can be understood that the condition of θ₁=15 degrees with θ₂=83.5 degrees improves the damping performance by 50%.

Under the condition of L₃/L₁=0.002 as illustrated in FIG. 10C, the damping ratio takes the lower limit value when θ₂ is 85 degrees. It can be understood that the condition of θ₁=15 degrees with θ₂=85 degrees improves the damping performance by 50%.

Under the condition of L₃/L₁=0.001 as illustrated in FIG. 10D, the damping ratio takes the lower limit value when θ₂ is 87 degrees. It can be understood that the condition of θ₁=15 degrees with θ₂=87 degrees improves the damping performance by 50%.

• (3) Case for θ₁=30 Degrees

FIGS. 11A to 11D are charts illustrating the relationship between rigidity and damping ratio where the braid angle θ₁ of the braid yarns 212 and 213 in the portion A in FIG. 4 is 30 degrees.

Under the condition of L₃/L₁=0.01 as illustrated in FIG. 11A, the line of measured values is out of the upper right area of the threshold line, which means that the damping performance cannot be improved by 50%.

Under the condition of L₃/L₁=0.004 as illustrated in FIG. 11B, the damping ratio takes the lower limit value when θ₂ is 89 degrees. It can be understood that the condition of θ₁=15 degrees with θ₂=89 degrees improves the damping performance by 50%.

Under the condition of L₃/L₁=0.002 as illustrated in FIG. 11C, the damping ratio takes the lower limit value when θ₂ is 89 degrees. It can be understood that the condition of θ₁=15 degrees with θ₂=89 degrees improves the damping performance by 50%.

Under the condition of L₃/L₁=0.001 as illustrated in FIG. 11D, the damping ratio takes the lower limit value when θ₂ is 89 degrees. It can be understood that the condition of θ₁=15 degrees with θ₂=89 degrees improves the damping performance by 50%.

• (4) Case for θ₁=45 Degrees

FIG. 12 is a chart illustrating the relationship between rigidity and damping ratio where the braid angle θ₁ of the braid yarns 212 and 213 in the portion A in FIG. 4 is 45 degrees and L₃/L₁ is 0.001. Although no performance chart is illustrated in FIG. 12 for the cases of L₃/L₁=0.01, L₃/L₁=0.004, and L₃/L₁=0.002 with the braid angle θ₁ of the braid yarns 212 and 213 in the portion A in FIG. 4 being 45 degrees, the lines of measured values are out of each upper right area of the threshold line, which means that the damping performance cannot be improved by 50%.

Under the condition of L₃/L₁=0.001 as illustrated in FIG. 12, the damping ratio takes the lower limit value when θ₂ is 89.9 degrees. It can be understood that the condition of θ₁=15 degrees with θ₂=89.9 degrees improves the damping performance by 50%.

• (5) Summary

The above results are summarized in the table below.

	TABLE 1
	{circle around (2)} END BRAID ANGLE
	60°	45°	30°	15°
{circle around (1)} MIDDLE REGION	0.01	NG	NG	NG	60°
LENGTH/TOTAL LENGTH	0.004	NG	NG	89°	83.5°
	0.002	NG	NG	89°	85°
	0.001	NG	89.9°	89°	87°

“NG” in Table 1 indicates that the line of measured values is out of the upper right area of the threshold line, which means that the damping performance cannot be improved by 50%.

As shown in Table 1, whether the long cylindrical portion 21a can have a vibration damping ratio improved by 50% while keeping a high rigidity depends on the relationship between the ratio L₃/L₁, θ₁, and θ₂. Specifically, for a smaller ratio L₃/L₁, θ₂ can take a certain value to improve the damping ratio by 50% even when θ₁ takes a relatively large value (45 degrees in Table 1).

For a smaller θ₁, θ₂ can take a relatively small value (60 degrees in Table 1) to improve the damping ratio by 50%.

• 7. Effect

The long cylindrical portions 21a of the reinforcing members 21 to 27 according to the embodiment each includes the carbon fiber braided structure 210 in which the axial yarns 211 and the braid yarns 212 and 213 each including carbon fibers are braided, and thus the long cylindrical portion 21a obtains high rigidity. That is, the long cylindrical portion 21a according to the embodiment obtains high rigidity because the long cylindrical portion 21a includes the braided braid yarns 212 and 213 and is reinforced by plastic resin.

The long cylindrical portion 21a according to the embodiment has the braid angle θ₂ of the braid yarns 212 and 213 in a region Ar₁ in the longitudinal middle larger than the braid angle θ₁ in the other region (a region in the end portion of the long cylindrical portion 21a, for example, the portion A in FIG. 4). The region Ar₁ therefore has a low modulus and thus obtains high vibration damping performance. The long cylindrical portion 21a having the region Ar₁ that is in the longitudinal middle and has the braid angle θ₂ larger than the braid angle θ₁ obtains high rigidity and superior vibration damping performance under a bending load.

As described using FIGS. 9 to 12 and Table 1, the long cylindrical portion 21a according to the embodiment has the braid angle θ₂ of 60 degrees or larger but smaller than 90 degrees, which reliably obtains superior vibration damping performance in the region Ar₁.

As described using FIGS. 9 to 12 and Table 1, the modulus in the region other than the middle portion of the long cylindrical portion 21a according to the embodiment can be increased by setting the braid angle θ₁ to 15 degrees or larger up to 45 degrees. Accordingly, the long cylindrical portion 21a according to the embodiment obtains high rigidity in the region other than the middle portion under a bending load.

The long cylindrical portion 21a according to the embodiment can obtain both high rigidity and superior vibration damping performance under a bending load by setting a ratio of the length L₃ to the length L₁ of the region Ar₁ to 0.001 or larger up to 0.01.

The long cylindrical portion 21a according to the embodiment can obtain higher rigidity by using the carbon fiber braided structure 210 including the axial yarn 211 braided to extend in the axis Ax₂₁₀.

As described using FIG. 8, the long cylindrical portion 21a according to the embodiment can advantageously obtain high rigidity with a small chance of stress concentration happening on a portion of the outer circumferential face under a bending load by setting the outer diameter D₃ same as the outer diameter D₄.

The long cylindrical portion 21a according to the embodiment has the larger braid angle θ₂ in the region Ar₁ than the braid angle θ₁, so that the braid yarns 212 and 213 in the region Ar₁ are more dense (the braid yarns 212 and 213 densely overlap) than the other region (an end, for example), resulting in the smaller inner diameter D₂ than the inner diameter D₁. Accordingly, the outer diameter D₃ and the outer diameter D₄ being the same provides high outward appearance quality and avoids local stress concentration and at the same time the region Ar₁ provides a low modulus to improve vibration damping performance.

The long cylindrical portion 21a according to the embodiment advantageously obtains high rigidity because the axial yarns 211 and the braid yarns 212 and 213 each comprise carbon fibers.

As described above, the reinforcing members 21 to 27 according to the embodiment each include the long cylindrical portion 21a which is a carbon fiber reinforced plastic member made by the braiding technique and therefore obtain high rigidity and superior vibration damping performance under a bending load.

Exemplary Modification

A carbon fiber braided structure 310 according to an exemplary modification will be described using FIG. 13. FIG. 13 is a schematic view illustrating a configuration of the carbon fiber braided structure 310 of a region Ar₁ in a longitudinal middle and the peripheral region of the region Ar₁ of a reinforcing member according to an exemplary modification of the present invention. The carbon fiber reinforced plastic member according to the exemplary modification is configured the same as the embodiment described above except for the carbon fiber braided structure 310. The description of the same configuration will not be repeated.

As illustrated in FIG. 13, the carbon fiber braided structure 310 according to the exemplary modification is also formed by braiding a plurality of axial yarns 311 and a plurality of braid yarns 312 and 313. Like the axial yarns 211 according to the embodiment described above, the axial yarns 311 linearly extend along an axis Ax₂₁₀ of the carbon fiber braided structure 310.

The braid yarns 312 and 313 are wound around the axis Ax₃₁₀ at a braid angle θ₂ in the region Ar₁ in the longitudinal middle and at a braid angle θ₁ in a region in the longitudinal end. This is the same as the embodiment described above, although not illustrated in FIG. 13.

The exemplary modification is different from the embodiment described above in that regions Ar₂ and Ar₃ are provided adjacent to both ends of the region Ar₁, regarding the longitudinal direction of the carbon fiber braided structure 310, where the braid yarns 312 and 313 are wound at a braid angle θ₃ in the region Ar₂ and Ar₃. The braid angle θ₃ satisfies the relationship expressed below.

θ₂>θ₃>θ₁   Formula 3

With the regions Ar₂ and Ar₃ provided to the carbon fiber braided structure 310 according to the exemplary modification, a steep change in the braid angles of the braid yarns 312 and 313 between the region Ar₁ in the middle and the region in the end, regarding the longitudinal direction of the carbon fiber braided structure 310, is moderated, and thereby the stress concentration caused by the change in the braid angle is reduced.

A reinforcing member including the carbon fiber braided structure 310 according to the exemplary modification is also configured the same as the reinforcing members 21 to 27 according to the embodiment described above except for the carbon fiber braided structure 310, and provides the same effect as described above.

Other Exemplary Modifications

In the embodiment and the exemplary modification described above, the reinforcing members 21 to 27 used for reinforcing the bottom of the vehicle body 1 are examples of a fiber reinforced plastic material. The present invention is however not limited to such members. For example, the fiber reinforced plastic material can be used as a strut tower bar.

The member according to the embodiment of the present invention can be used not only as a member for reinforcing a certain portion but as a structural member itself that obtains the effect described above. Regarding a vehicle body, for example, the member can be used as a roof side rail, a center pillar, or a front pillar.

Not only for a vehicle body of an automobile, the member configured as described above can be used for various structural bodies (for example, an industrial machines).

In the embodiment and the exemplary modification described above, the long cylindrical portion 21a having a hollow cylindrical shape is an example of a fiber reinforced plastic member. The present invention is not limited to such a member. For example, the member can be used for a solid member and the cross-section of a member may not always be a circular shape but may be an oval shape, an elliptical shape, or a polygonal shape.

The embodiment and the exemplary modification described above have exemplary configurations in which a plurality of axial yarns 211 or 311 are provided throughout the longitudinal direction of the long cylindrical portion 21a. The present invention is not limited to such a configuration. For example, a plurality of the axial yarns 211 or 311 in the region Ar₁ in the longitudinal middle may partially or entirely be eliminated. Such a configuration allows easily striking a balance between rigidity and vibration damping performance in the middle region.

In the embodiment and the exemplary modification described above, both the group of the braid yarns 212 or 312 and the group of the braid yarns 213 or 313 have the braid angle θ₂ in the region Ar₁ in the longitudinal middle larger than the braid angle θ₁ in the other region. The present invention is not limited to such a configuration. For example, only one of the group of the braid yarns 212 or 312 and the group of the braid yarns 213 or 313 may have the braid angle in the region in the longitudinal middle larger than the braid angle in the other region.

In the embodiment and the exemplary modification described above, the braid yarns 212 or 312 and braid yarns 213 or 313 have the braid angle θ₂ in the region Ar₁ in the longitudinal middle larger than the braid angle θ₁ in the other region. The region where the braid angle is larger than the braid angle in the other region is not limited to the longitudinal middle of the fiber reinforced plastic member. For example, a region closer to the end than the longitudinal middle of the fiber reinforced plastic member may have the braid angle of the braid yarns larger than the other region. The region of the fiber reinforced plastic member having the large braid angle of the braid yarns is not limited to a region in a particular portion in the longitudinal direction. A plurality of such regions may be provided.

In the embodiment and the exemplary modification described above, the carbon fiber reinforced plastic resin is an example of a fiber reinforced plastic resin. The present invention is not limited to such a plastic resin. For example, glass fiber reinforced plastic resin (GFRP), aramid fiber reinforced plastic resin (ArFRP), silicon carbide fiber reinforced plastic resin (SiCFRP), or fiber reinforced plastic resin containing metal fibers, such as non-ferrous metal may be used.

An illumination device for a vehicle described in relation with the embodiment mainly includes the features described below.

A fiber reinforced plastic member according to the embodiment is made of a fiber reinforced plastic resin and extends in a specific direction. The fiber reinforced plastic member comprises a fiber-braided structure. The fiber-braided structure includes first braid yarns wound to intersect the specific direction at a first braid angle, and a second braid yams wound to intersect the specific direction at a second braid angle, the first braid yarns and the second braid yarns being braided together. The fiber-braided structure includes a predetermined region between both ends, regarding a longitudinal direction of the fiber reinforced plastic member. At least one of the first braid angle and the second braid angle in the predetermined region is larger than the braid angle in an other region other than the predetermined region.

The fiber reinforced plastic member having a configuration described above includes a fiber-braided structure in which fibers are braided, and thus obtains high rigidity. That is, the fiber reinforced plastic member includes the first braid yarns and the second braid yarns braided together, is reinforced with plastic resin, and thus has high rigidity.

The fiber reinforced plastic member configured as described above has the larger first braid angle and the larger second braid angle in the predetermined region than the braid angle in the other region, and thus has a low modulus in the predetermined region, obtaining high vibration damping performance. With the predetermined region in which at least one of the first braid angle and the second braid angle is larger than the angle in the other region is provided in the longitudinal middle, the member according to the embodiment obtains high rigidity and superior vibration damping performance under a bending load.

The fiber reinforced plastic member according to the embodiment may have the first braid angle and the second braid angle set to 60 degrees or larger but smaller than 90 degrees.

By setting the first braid angle and the second braid angle to values of 60 degrees or larger but smaller than 90 degrees, the predetermined region reliably obtains superior vibration damping performance.

The fiber reinforced plastic member according to the embodiment may have the braid angles of the first braid yarns and the second braid yarns in the other region set to 15 degrees or larger up to 45 degrees.

By setting the braid angles of the first braid yarns and the second braid yarns in the other region to 15 degrees or larger up to 45 degrees, the modulus in the other region can be raised. Using the configuration described above, the other region obtains high rigidity when the fiber reinforced plastic member is subjected to a bending load.

The fiber reinforced plastic member according to the embodiment may have the ratio of the longitudinal length of the predetermined region to the total longitudinal length of the member set to 0.001 or larger up to 0.01.

By setting the ratio of the longitudinal length of the predetermined region to the total longitudinal length of the fiber reinforced plastic member to 0.001 or larger up to 0.01, both high rigidity and superior vibration damping performance under a bending load can be obtained.

The fiber-braided structure of the fiber reinforced plastic member according to the embodiment may include, in addition to the first braid yarns and the second braid yarns, axial yarns braided to extend in the specific direction.

As described above, with the axial yarns braided in the fiber-braided structure to extend in the specific direction, the fiber reinforced plastic member obtains further high rigidity.

The fiber reinforced plastic member according to the embodiment may have a constant outer diameter throughout the longitudinal direction.

As described above, with the outer diameter of the fiber reinforced plastic member having a constant size throughout the longitudinal direction, the fiber reinforced plastic member advantageously obtains high rigidity with a small chance of local stress concentration happening in the outer circumferential face when subjected to a bending load.

The fiber reinforced plastic member according to the embodiment may be a hollow cylindrical member having the inner diameter of the predetermined region smaller than the inner diameter of the other region.

Since at least one of the first braid angle and the second braid angle takes a larger value in the predetermined region than in the other region, the density of the braid yarns becomes high (the braid yarns densely overlap) in the predetermined region, resulting in the small inner diameter in the predetermined region of the fiber reinforced plastic member. Accordingly, the predetermined region having the inner diameter smaller than the other region has a low modulus and obtains high vibration damping performance.

The fiber reinforced plastic member according to the embodiment may have the first braid yarns and the second braid yarns made of carbon fibers.

Use of the first braid yarns and the second braid yarns made of carbon fibers is advantageous in obtaining high bending rigidity.

The fiber reinforced plastic member made by the braiding technique obtains high rigidity and superior vibration damping performance under a bending load.

This application is based on Japanese Patent application No. 2018-161400 filed in Japan Patent Office on Aug. 30, 2018, the contents of which are hereby incorporated by reference.

Although the present invention has been fully described by way of example with reference to the accompanying drawings, it is to be understood that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modifications depart from the scope of the present invention hereinafter defined, they should be construed as being included therein.

Claims

1. A fiber reinforced plastic member, which is made of fiber reinforced plastic resin and

extends in a specific direction,

the fiber reinforced plastic member comprising a fiber-braided structure,

the fiber-braided structure including

first braid yarns wound to intersect the specific direction at a first braid angle, and

second braid yarns wound to intersect the specific direction at a second braid angle, the first braid yarns and the second braid yarns being braided together, wherein

the fiber-braided structure includes a predetermined region between both ends, regarding a longitudinal direction of the fiber reinforced plastic member, at least one of the first braid angle and the second braid angle in the predetermined region being larger than the braid angle in an other region other than the predetermined region.

2. The fiber reinforced plastic member according to claim 1, wherein the first braid angle and the second braid angle are 60 degrees or larger but smaller than 90 degrees.

3. The fiber reinforced plastic member according to claim 1, wherein

the first braid angle of the first braid yarns and the second braid angle of the second braid yarns in the other region are 15 degrees or larger up to 45 degrees.

4. The fiber reinforced plastic member according to claim 1, wherein

a ratio of a longitudinal length of the predetermined region to a total longitudinal length of the fiber reinforced plastic member is 0.001 or larger up to 0.01.

5. The fiber reinforced plastic member according to claim 1, wherein

the fiber-braided structure includes, in addition to the first braid yarns and the second braid yarns, axial yarns braided to extend in the specific direction.

6. The fiber reinforced plastic member according to claim 1, wherein

an outer diameter of the fiber reinforced plastic member is constant throughout the longitudinal direction.

7. The fiber reinforced plastic member according to claim 1, wherein

the fiber reinforced plastic member has a form of a hollow cylindrical member, and

the fiber reinforced plastic member has an inner diameter smaller in the predetermined region than in the other region.

8. The fiber reinforced plastic member according to claim 1, wherein

the first braid yarns and the second braid yarns include carbon fibers.