JP7614060B2 - Composite Materials - Google Patents

Description

The present invention relates to a composite material containing fibers in a resin.

Patent Document 1 discloses a fiber-reinforced resin member that increases the fiber volume ratio of the fastening portion where a separate part is attached and suppresses the impregnation of the fastening portion with resin, thereby enabling easy bolt tightening without pre-drilling bolt holes. In this fiber-reinforced resin member, by impregnating the fastening portion with resin, deterioration and deformation of the fastening portion are suppressed.

Japanese Patent Application Publication No. 7-256769

However, in fiber-reinforced resin components such as those in Patent Document 1, increasing the fiber density may result in the resin not being able to penetrate between the fibers even when impregnated with resin. In other words, increasing the fiber density at the fastening portion with another component may actually weaken the bond strength between the fibers, which may cause deterioration and deformation of the fastening portion.

The present invention aims to provide a composite member that suppresses deterioration and deformation of the fastening parts.

The composite member described in claim 1 has a main body portion containing resin as a base material and fibers in the resin, a first region in the main body portion that is composed of the fibers to which nanomaterial has been added and that includes a fastening portion for fastening to another member, and a second region in the main body portion that is provided around the first region and that contains fewer fibers to which nanomaterial has been added than in the first region.

The composite member described in claim 1 contains fibers in a resin, and is fastened to another member at a fastening portion provided in the main body. The main body of the composite member has a first region having a fastening portion, and a second region provided around the first region. Since the fibers included in the first region contain more nanomaterial than the fibers included in the second region, the density of the nanomaterial in the fastening portion is higher than in the surrounding area. Therefore, with this composite member, the bonding strength between the fibers can be ensured, and deterioration and deformation of the fastening portion can be suppressed.

The composite member described in claim 2 is the composite member described in claim 1, in which the boundary between the first region and the second region is inclined with respect to the fastening direction.

The composite member described in claim 2 can ensure the adhesion area between two regions with different levels of nanomaterial addition, and ensure the bonding strength at the boundary between the two regions.

The composite member described in claim 3 is the composite member described in claim 1 or 2, in which the thickness of the first region in the fastening portion is equal to or greater than half the thickness of the main body portion.

According to the composite member described in claim 3, by setting the lower limit of the thickness of the first region to half the thickness of the main body, it is possible to suppress deterioration and deformation of the fastening portion while reducing the amount of expensive nanomaterial used.

The composite member described in claim 4 is the composite member described in any one of claims 1 to 3, in which the outer edge of the first region is in the range of 1.5D to 5D, where D is the diameter of the bolt fastened in the fastening portion.

According to the composite member described in claim 4, by setting the range of the first region to a range of 1.5 to 5 times the diameter of the bolt, it is possible to suppress deterioration and deformation of the fastening portion while reducing the amount of costly nanomaterial used.

The composite material described in claim 5 is the composite material described in any one of claims 1 to 4, in which the fibers to which the nanomaterial has been added and the fibers to which the nanomaterial has not been added are mixed in the second region near the boundary between the first region and the second region, and the fibers to which the nanomaterial has not been added are composed of the fibers to which the nanomaterial has not been added in places in the second region away from the boundary.

According to the composite material described in claim 5, by suppressing a sudden change in the degree of nanomaterial addition at the boundary between the first region and the second region, peeling at the boundary can be suppressed.

The composite material described in claim 6 is the composite material described in any one of claims 1 to 5, in which the nanomaterial is derived from a natural material.

The composite member described in claim 6 can suppress cost increases compared to using carbon nanotubes as the nanomaterial, and can also achieve carbon neutrality.

The present invention allows for increased fiber density in the fastening section.

FIG. 2 is a plan view of the panel and reinforcement of the first embodiment. A cross-sectional view of the joint between the panel and the reinforcement in the first embodiment. A cross-sectional view of the joint between a panel and a reinforcement in the second embodiment. A cross-sectional view of the joint between a panel and a reinforcement in the third embodiment. A cross-sectional view of the joint between a panel and a reinforcement in the fourth embodiment.

[First embodiment]
1 and 2 show a panel 10 of the present embodiment and a reinforcement 30 to which the panel 10 is fixed. The reinforcement 30 is an example of another member. The panel 10 as a composite member includes a main body 12 made of carbon fiber reinforced plastics (CFRP). The main body 12 has an insertion hole 14A through which a bolt 42 is inserted, and the bolt 42 is screwed into a nut 44 to form a portion to which a fastening force is applied as a fastening portion 14. Here, the portion to which the fastening force is applied is a peripheral portion of the insertion hole 14A, and includes at least a range in contact with the head of the bolt 42.

As shown in FIG. 2, the main body 12 of the panel 10 has a first region 12A including the fastening portion 14, and a second region 12B provided around the first region. In this embodiment, the boundary portion 12C between the first region 12A and the second region 12B is inclined with respect to the fastening direction of the bolt 42, i.e., the axial direction. More specifically, it is inclined in a direction away from the insertion hole 14A as it goes from the bottom to the top of the main body 12.

The panel 10 also includes resin 20 as a base material and carbon fibers 22, which are fibers contained in the resin 20. In FIG. 2, the extension direction of the carbon fibers 22 is set to one direction extending from the front to the back of the drawing, but this is not limited thereto, and the extension direction of the carbon fibers 22 may be changed for each layer, or the carbon fibers 22 may be woven vertically and horizontally (the same applies to other embodiments). Here, the carbon fibers 22 in the first region 12A have carbon nanotubes 24, which are nanomaterials, added to their surfaces. The state in which the carbon nanotubes 24 are added to the carbon fibers 22 includes not only a state in which the carbon nanotubes 24 are attached to the surface of the carbon fibers 22, but also a state in which the carbon nanotubes 24 are dispersed on and around the surface of the carbon fibers 22. On the other hand, the carbon nanotubes 24 are not added to the carbon fibers 22 in the second region 12B.

In addition, if the weight ratio of the carbon fibers 22 to which the carbon nanotubes 24 have been added is smaller than that in the first region 12A, the carbon nanotubes 24 may be added to the carbon fibers 22 in the second region 12B.

The panel 10 of this embodiment can be manufactured by stacking prepregs in which carbon fibers 22 are impregnated with resin 20, and then molding by pressing. Here, the carbon fibers 22 in the prepregs that make up the first region 12A have carbon nanotubes 24 added to their surfaces in advance. In addition, near the fastening portion 14, a slanted boundary portion 12C can be formed by stacking the prepregs with carbon nanotubes 24 while shifting them radially of the insertion hole 14A.

The main body 12 of the panel 10 may be manufactured by a method of impregnating a molded body of carbon fiber 22 shaped to the main body 12 with liquid resin, or by press molding a sheet molding compound (SMC).

As described above, in this embodiment, carbon nanotubes 24 are added to the carbon fibers 22 contained in the first region 12A, and carbon nanotubes 24 are not added to the carbon fibers 22 contained in the second region 12B. Therefore, the density of the carbon nanotubes 24 in the fastening portion 14 is higher than that in the surrounding area of the fastening portion 14.

For example, as disclosed in JP 2019-59871 A, it is known that in carbon fiber reinforced resin, providing carbon nanotubes on the surface of the carbon fiber improves the peel strength against the base resin and improves the mechanical strength. Therefore, as in this embodiment, by using carbon fibers 22 with carbon nanotubes 24 added to the surface near the fastening portion 14 where the fastening force is applied, the mechanical strength of the main body portion 12 can be improved without increasing the density of the carbon fibers 22. This makes it possible to suppress deterioration and deformation of the fastening portion 14.

In addition, since the mechanical strength of the main body 12 can be improved without increasing the density of the carbon fibers 22, insufficient impregnation of the resin 20 is suppressed when the panel 10 is manufactured by the above-mentioned method of impregnating the resin 20. Furthermore, this embodiment is advantageous in terms of cost because it does not require additional parts such as metal collars or additional manufacturing steps compared to the case where deterioration and deformation of the fastening portion 14 are suppressed by providing a metal collar or the like in the insertion hole 14A.

On the other hand, nanomaterials such as carbon nanotubes 24 are generally expensive, and there is an issue that applications are limited due to cost when nanomaterials are used for the entire part. In contrast, in this embodiment, carbon nanotubes 24 are added only to the first region 12A including the fastening portion 14, so manufacturing costs are reduced compared to when carbon nanotubes 24 are used for the entire main body portion 12.

In addition, when carbon fiber reinforced resin has multiple regions with different mechanical strengths, it is difficult to ensure the bonding strength at the boundary between the regions. In contrast, in the panel 10 of this embodiment, the boundary 12C between the first region 12A and the second region 12B is inclined with respect to the axial direction, which is the fastening direction of the bolt 42. Therefore, according to this embodiment, the bonding area between the first region 12A and the second region 12B can be secured, and the bonding strength between the two can be secured, compared to when the boundary 12C is formed perpendicular to the fastening direction.

Second Embodiment
The second embodiment differs from the first embodiment in the arrangement of the first region 12A and the second region 12B. The differences from the first embodiment will be described below. Note that the same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and detailed description thereof will be omitted.

As shown in FIG. 3, in this embodiment, the insertion hole 14A is arranged to straddle the first region 12A and the second region 12B, and the fastening portion 14 is included in both the first region 12A and the second region 12B. The range in which the first region 12A is arranged in the thickness direction of the main body portion 12 is determined by the thickness of the main body portion 12. Specifically, the thicknesses t1 and t2 of the first region 12A in the fastening portion 14 are set within a range of 80% to 90% of the thickness T of the main body portion 12. In FIG. 3, the thickness t1 of the first region 12A is the thickness on the radial inner side of the fastening portion 14, and the thickness t2 of the first region 12A is the thickness on the radial outer side of the fastening portion 14.

In the fastening portion 14 having the structure of this embodiment, the thicknesses t1 and t2 of the first region 12A are set to at least half the thickness T of the main body portion 12, thereby ensuring mechanical strength. Therefore, according to the panel 10 of this embodiment, by reducing the first region 12A in the thickness direction of the main body portion 12, it is possible to suppress deterioration and deformation of the fastening portion 14 while reducing the amount of carbon nanotubes 24 used, which are expensive. In addition, this embodiment has the same effects as the first embodiment.

[Third embodiment]
The third embodiment differs from the first and second embodiments in the arrangement of the first region 12A and the second region 12B. The differences from the first embodiment will be described below. Note that the same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and detailed description thereof will be omitted.

As shown in FIG. 4, in this embodiment, the insertion hole 14A is disposed in the first region 12A, but the fastening portion 14 is included in both the first region 12A and the second region 12B. The range in which the first region 12A is disposed in the width direction of the main body 12 is determined by the diameter of the bolt 42. Specifically, the outer diameter d of the outer edge of the first region 12A in the fastening portion 14 is set in the range of 1.5D to 5D, where D is the diameter of the bolt 42.

In the fastening portion 14 having the structure of this embodiment, the outer diameter d of the first region 12A is set in the range of 1.5 to 5 times the diameter D of the bolt 42, thereby ensuring mechanical strength. Therefore, according to the panel 10 of this embodiment, by reducing the first region 12A in the width direction of the main body portion 12, it is possible to suppress deterioration and deformation of the fastening portion while reducing the amount of carbon nanotubes 24 used, which are expensive. In addition, this embodiment has the same effects as the first embodiment.

[Fourth embodiment]
The fourth embodiment is different from the first embodiment in the structure near the boundary 12C between the first region 12A and the second region 12B. The differences from the first embodiment will be described below. Note that the same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and detailed description thereof will be omitted.

As shown in FIG. 5, in this embodiment, in the second region 12B near the boundary 12C, carbon fibers 22 to which carbon nanotubes 24 have been added and carbon fibers 22 to which carbon nanotubes 24 have not been added are mixed. Furthermore, in the second region 12B, in places away from the boundary 12C, carbon fibers 22 to which carbon nanotubes 24 have been added are not present.

According to this embodiment, by suppressing a sudden change in the degree of addition of carbon nanotubes 24 at boundary portion 12C, which is the boundary between first region 12A and second region 12B, peeling at boundary portion 12C can be suppressed.

[Fifth embodiment]
In the fourth embodiment, carbon nanotubes are used as the nanomaterial, but in the fifth embodiment, cellulose nanofibers derived from natural materials are used as the nanomaterial. Note that the structure other than the nanomaterial is the same as in the fourth embodiment, so detailed description will be omitted.

In this embodiment, the same effect as in the fourth embodiment can be obtained. Note that, like carbon nanotubes, cellulose nanofibers are also expensive materials, but like carbon nanotubes, only a small amount of cellulose nanofiber needs to be added. Therefore, according to this embodiment, the increase in cost of the panel 10 can be suppressed. Also, cellulose nanofibers are natural materials derived from plants. That is, because carbon dioxide is absorbed by photosynthesis during the growth process of plants, so-called carbon neutrality can be achieved by using cellulose nanofibers as a nanomaterial.

In the first to third embodiments, cellulose nanofibers may be used instead of carbon nanotubes. In this case, in addition to the effects of each embodiment, it is possible to suppress cost increases and achieve carbon neutrality.

Below, examples of the present invention will be described with reference to Tables 1 and 2. In each table, "CNT" stands for carbon nanotube, and "CNF" stands for cellulose nanofiber.

Table 1 summarizes the structures and effects of Examples 1 to 5. Example 1 has a structure similar to that of the first embodiment shown in FIG. 2. Example 2 has a structure similar to that of the second embodiment shown in FIG. 3, in which the thickness of the first region 12A in the fastening portion 14 is set to 50% of the main body portion 12. Example 3 has a structure similar to that of the third embodiment shown in FIG. 4, in which the area of the first region 12A in the fastening portion 14 is set to 1.2 times that of the bolt 42. Example 4 has a structure similar to that of the fourth embodiment shown in FIG. 5, in which carbon nanotubes 24 are mixed in near the boundary portion 12C. Example 5 has a structure similar to that of Example 4, in which cellulose nanofibers are used instead of the carbon nanotubes 24.

According to each embodiment, by including carbon nanotubes 24 or cellulose nanofibers in the fastening portion, it is possible to ensure the joint strength even 100 days after the bolt 42 is fastened, and to reduce costs. Note that in the case of embodiment 2, since the fastening portion 14 includes a second region 12B in the thickness direction that does not include carbon nanotubes 24, the joint strength is lower than in the other embodiments, but the amount of carbon nanotubes 24 used is reduced, which is advantageous in terms of cost.

Table 2 summarizes the structures and effects of Comparative Examples 1 to 6. Comparative Example 1 is an example in which the resin 20 does not contain carbon fiber 22, and a metal collar is provided in the insertion hole 14A. Comparative Example 2 is an example in which the main body 12 is formed from carbon fiber 22 to which no carbon nanotubes 24 have been added. Comparative Example 3 is an example in which the entire main body 12 is formed from resin 20 that does not contain carbon fiber 22, but does contain carbon nanotubes 24. Comparative Examples 4 to 6 are examples in which carbon fiber 22 to which carbon nanotubes 24 have been added is used for the entire main body 12.

Comparative Example 1 is disadvantageous in terms of cost compared to the other Examples, because the number of steps increases due to gluing the metal collar to the insertion hole 14A, etc.Comparative Example 2 increases the density of the carbon fiber 22, but does not contain carbon nanotubes 24, and the joint strength decreases 100 days after the bolt 42 is fastened, causing the bolt 42 to loosen. This is due to creep occurring in the fastening portion 14.Comparative Example 3 is able to ensure a certain level of joint strength even without containing carbon fiber 22. However, because it contains a large amount of carbon nanotubes 24, it is the most disadvantageous in terms of cost.Comparative Examples 4 to 6 contain carbon nanotubes 24 throughout the main body 12, so they are able to ensure a certain level of joint strength, but are disadvantageous in terms of cost compared to the other Examples.

As described above, according to each embodiment, it is possible to ensure the joining strength without increasing the cost compared to each comparative example. In other words, deterioration and deformation of the fastening portion 14 are suppressed.

[remarks]
In each of the above-described embodiments, the panel 10 as a composite member is made of carbon fiber reinforced plastics (CFRP), but this is not limiting. For example, the panel 10 may be made of glass fiber reinforced plastics (GFRP).

In the above first to fourth embodiments (FIGS. 2 to 5), the carbon nanotubes 24 are shown attached to the surface of the carbon fibers 22, but this is not limiting, and the carbon nanotubes 24 may be present dispersed on the surface of the carbon fibers 22 and in their surroundings. In this case, the carbon nanotubes 24 are also present between the carbon fibers 22 in the first region 12A. As in the fifth embodiment, the cellulose nanofibers may also be dispersed in the same manner when cellulose nanofibers are used as the nanomaterial instead of carbon nanotubes.

In the first to fourth embodiments, carbon nanotubes 24 are used as the nanomaterial. Furthermore, in the fifth embodiment, cellulose nanofibers are used as the nanomaterial. However, this is not limited thereto, and other nanomaterials such as fullerenes may also be used.

The second to fourth embodiments described above may be configured in combination with each other. For example, carbon fibers 22 to which carbon nanotubes 24 have been added may be mixed with carbon fibers 22 to which carbon nanotubes 24 have not been added near the boundary portion 12C of the second or third embodiment. Note that the aspects of each embodiment may also be combined when cellulose nanofibers are used as the nanomaterial instead of carbon nanotubes.

The present invention is suitable for joining structural parts of a vehicle. For example, it can be applied to joining a bulkhead and a reinforcement. When the present invention is applied to structural parts of a vehicle, the strength of the fastening portion 14 is ensured, and deterioration and deformation of the fastening portion 14 are suppressed, thereby increasing the torsional rigidity of the vehicle body.

10 Panel (composite material)
12 Main body portion 12A First region 12B Second region 12C Boundary portion 14 Fastening portion 20 Resin 22 Carbon fiber (fiber)
24 Carbon nanotubes (nanomaterials)
30 Reinforcement (other components)
42 Volts

Claims (5)

A main body portion including a resin as a base material and fibers in the resin;
A first region in the main body portion is made of the fiber to which a nanomaterial is added and includes a fastening portion for fastening the main body portion to another member;
a second region provided around the first region in the main body and having fewer fibers to which the nanomaterial is added than in the first region;
having
In the second region near the boundary between the first region and the second region, the fibers to which the nanomaterial has been added and the fibers to which the nanomaterial has not been added are mixed,
A composite member , wherein in the second region, in areas away from the boundary portion, the fibers are composed of fibers to which the nanomaterial is not added . The composite member according to claim 1, wherein the boundary between the first region and the second region is inclined with respect to the fastening direction. The composite member according to claim 1 or 2, wherein the thickness of the first region in the fastening portion is equal to or greater than half the thickness of the main body portion. The composite member according to any one of claims 1 to 3, wherein the outer edge of the first region is in the range of 1.5D to 5D, where D is the diameter of the bolt fastened in the fastening portion. The composite material according to any one of claims 1 to 4 , wherein the nanomaterial is derived from a natural material.