Fiber-reinforced resin molded article and method for manufacturing same

A fiber-reinforced resin molding includes a core layer and a pair of skin layers. The core layer includes a nonwoven fabric and impregnating resin that has been impregnated in the nonwoven fabric. The skin layers include fibers and a matrix resin that covers the fibers. The fibers and a matrix resin of the skin layers are joined to both surfaces of the core layer. The skin layers each have recesses that are formed on side surfaces that face the core layer such that a portion of the fibers in the matrix resin are exposed, and where portions of the nonwoven fabric and the impregnating resin have penetrated the recesses.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national stage application of International Application No. PCT/JP2016/063531, filed on May 2, 2016.

BACKGROUND

Field of the Invention

The present invention relates to a fiber-reinforced resin molding and a method for producing same.

Background Information

A fiber-reinforced resin molding configured comprising FRP (Fiber Reinforced Plastic), which is a type of composite material, is known from the prior art (refer, for example, to Japanese Patent No. 4615398—Patent Document 1).

Patent Document 1 discloses a carbon fiber composite material molding obtained by sandwiching a core layer of nonwoven fabric between two carbon fiber layers, which form skin layers, to form a stacked body, and impregnating the stacked body with an impregnating resin, followed by curing.

SUMMARY

In the carbon fiber composite material molding described above, the skin layers and the core layer are joined only by resin, and the joining force between the skin layers and the core layer is low; consequently, when a load is applied to the carbon fiber composite material molding, there is the possibility that the skin layers and the core layer between the layers will separate.

Thus, the object of the present invention is to prevent the skin layer from separating from the core layer by increasing the joining force between the skin layer and the core layer.

A first feature of the present invention is a fiber-reinforced resin molding comprising a core layer comprising a nonwoven fabric and impregnating resin that has been impregnated into the nonwoven fabric, and a pair of skin layers comprising fibers and a matrix resin that covers the fibers. The skin layers have recesses that are formed in the core layer side surfaces and in which some of the fibers in the matrix resin are exposed, and portions of the nonwoven fabric and the impregnating resin penetrate the recesses.

A second aspect of the present invention is a method for producing a fiber-reinforced resin molding. The production method includes a step for forming recesses in which some of the fibers in the matrix resin the skin layers are exposed to the core layer side surfaces, and a step for disposing a nonwoven fabric between a pair of the skin layers, causing portions of the nonwoven fabric and the impregnating resin to penetrate the recesses, and joining the skin layers and the core layer in that state.

According to the present invention, it is possible to prevent separation of the skin layers from the core layer by increasing the joining force between the skin layers and the core layer.

DETAILED DESCRIPTION OF THE EMBODIMENTS

A fiber-reinforced resin molding10according to an embodiment of the present invention will now be described with reference toFIGS. 1 to 3.

The fiber-reinforced resin molding10can be applied, for example, to vehicle component members, such as a hood (bonnet), a bumper, a trunk lid, a rear gate, a fender panel, a side body panel, and a roof panel. In addition, the fiber-reinforced resin molding10is not limited to vehicle component members and can be applied to various types of component members.

The fiber-reinforced resin molding10comprises a core layer11and a pair of skin layers12,12that are joined to both surfaces of the core layer11, as illustrated inFIGS. 1 and 2.

The core layer11is a nonwoven fabric layer comprising a nonwoven fabric13and an impregnating resin14that has been impregnated in the nonwoven fabric13. The thickness of the core layer11is, for example, about 0.2 mm-10.0 mm. The nonwoven fabric13is formed from known fibers, such as cotton, rayon, nylon, polyester, polypropylene, and aramid fibers. The impregnating resin14is formed from a thermosetting resin, such as epoxy resin, unsaturated polyester resin, vinyl ester resin, and phenol resin. In addition, the impregnating resin14may be formed from a thermoplastic resin, such as polyamide resin, polyolefin resin, dicyclopentadiene resin, and polyurethane resin.

The skin layers12are made up of a fiber layer comprising fibers15and a matrix resin16that covers the fibers15. That is, the skin layers12are what is referred to as an FRP (fiber-reinforced resin). The thicknesses of the skin layers12are, for example, about 0.4 mm to 5.0 mm. The fibers15can be formed from various fibers, such as carbon fiber, glass fiber, and aramid fiber (Kevlar fiber). The matrix resin16can be formed from thermosetting resin, such as epoxy resin, unsaturated polyester resin, vinyl ester resin, and phenol resin. In addition, the matrix resin16can be formed from a thermoplastic resin, such as polyamide resin, polyolefin resin, dicyclopentadiene resin, and polyurethane resin.

The impregnating resin14of the core layer11and the matrix resin16of the skin layers12can be of the same or of different types. From the standpoint of enhancing the joining force between the core layer11and the skin layers12, the impregnating resin14of the core layer11and the matrix resin16of the skin layers12are preferably resins that have high affinity.

The skin layers12have a plurality of recesses18formed on side surface17facing the core layer11such that portions of the fibers15in the matrix resin16are exposed. The matrix resin16of the skin layers12and the impregnating resin14of the core layer11are joined (bonded), in a state in which portions of the nonwoven fabric13and the impregnating resin14have penetrated the recesses18. Thus, the fiber-reinforced resin molding10is formed in the joint portion19between the core layer11and the skin layers12and includes a plurality of mixed regions20in which the nonwoven fabric13and the fibers15are mixed.

The recesses18and the mixed regions20are arranged at intervals in the longitudinal direction and the lateral direction on the surfaces of the skin layers12, as illustrated inFIG. 1. In the figure, the recesses18and the mixed regions20are arranged at equal intervals, but no limitation is imposed thereby, and the intervals need not be equal.

In addition, the positions of the recesses18and the mixed regions20in the in-plane direction of the skin layers12(direction that is parallel to the surface) are asymmetrical relative to the core layer11between one and the other of the pair of skin layers12,12, as illustrated inFIG. 2. That is, the recesses18and the mixed regions20are arranged in different locations between one and the other of the pair of skin layers12,12. However, no limitation is imposed thereby; the positions of the recesses18and the mixed regions20in the in-plane direction of the skin layer12can be symmetrical relative to the core layer11between one and the other of the pair of skin layers12,12.

Next, a method for producing the fiber-reinforced resin molding10according to the present embodiment will be described.

1. Application of Wax

First, a wax21is applied to a sheet or a bundle of fiber15, as illustrated inFIG. 3A, in randomly distributed fashion and the applied wax21is cured and hardened.

Thermoplastic resins such as polyvinyl alcohol (PVA), polyethylene (PE), or polypropylene (PP), for example, may be used as the wax21. Polyethylene and polypropylene have relatively low melting points; therefore, when polyethylene or polypropylene is used as the wax21, it is necessary to set the injection temperature of the matrix resin16to be less than or equal to the melting points of polyethylene and polypropylene.

2. Injection of Matrix Resin into the Mold

Next, the fibers15are placed in the mold and the matrix resin16is injected into the mold to impregnate the fibers15with the matrix resin16, as illustrated inFIG. 3B. Then, the impregnated matrix resin16is cured and hardened to prepare the skin layer12.

3. Removal of Wax

Next, the wax21is melted with warm water or a solvent to form recesses18on the skin layer12, as illustrated inFIG. 3C.

That is, in the present embodiment, the lost wax method is used to form the recesses18on the skin layer12.

Next, the nonwoven fabric13is stacked between a pair of skin layers12,12to prepare a stacked body22, as illustrated inFIG. 3D.

5. Injection of Impregnating Resin into the MOLD

Next, the stacked body22is placed in a mold, impregnating resin14is injected into the mold, and the nonwoven fabric13is impregnated with the impregnating resin14, as illustrated inFIG. 3E. In this step to inject the impregnating resin14into a mold, portions of the nonwoven fabric13and the impregnating resin14are made to penetrate each recess18, and the fibers15that are exposed due to the removal of the wax21become entangled with the nonwoven fabric13. Then, the impregnating resin14is cured and hardened to prepare a fiber-reinforced resin molding10.

That is, in the present embodiment, the RTM molding (Resin Transfer Molding) method is used to mold the stacked body22.

The action and effects of the present embodiment will be described below.

(1) A fiber-reinforced resin molding10according to the present embodiment comprises a core layer11comprising a nonwoven fabric13and impregnating resin14that has been impregnated into the nonwoven fabric13; and a pair of skin layers12,12comprising fibers15and a matrix resin16that covers the fibers15and that are joined to both surfaces of the core layer (11). The skin layers12have recesses18that are formed on side surfaces17facing the core layer11such that a portion of the fibers15in the matrix resin16are exposed, and portions of the nonwoven fabric13and the impregnating resin14have penetrated the recesses18.

In the fiber-reinforced resin molding10according to the present embodiment, the matrix resin16of the skin layer12and the impregnating resin14of the core layer11are joined in a state in which portions of the nonwoven fabric13and the impregnating resin14have penetrated the recesses18. That is, mixed regions20, in which the nonwoven fabric13and the fibers15are mixed, are formed in the joint portion19between the core layer11and the skin layer12. Thus, it is possible to enhance the joining force between the skin layer12and the core layer11and to reduce the possibility that the skin layer12and the core layer11will separate between the layers, even if a load is applied to the fiber-reinforced resin molding10.

Therefore, according to the fiber-reinforced resin molding10of the present embodiment, it is possible to prevent the skin layer12from separating from the core layer11by increasing the joining force between the skin layer12and the core layer11.

(2) The positions of the recesses18in the in-plane direction of the skin layer12are asymmetrical relative to the core layer11between one and the other of the pair of skin layers12,12.

Thus, it is possible to shift the positions of the mixed regions20, in which the nonwoven fabric13and the fibers15are mixed, in the in-plane direction of the skin layer12between one and the other of the pair of skin layers12,12, and to thereby prevent the generation of locations with low densities of the nonwoven fabric13in the core layer11.

(3) The method for producing a fiber-reinforced resin molding10according to the present embodiment comprises a step (Step 1) for forming recesses18in which portions of the fibers15in the matrix resin16are exposed on side surfaces17of the skin layer12facing the core layer11, and a step (Step 2) for disposing the nonwoven fabric13between the pair of skin layers12,12, causing some of the nonwoven fabric13and impregnating resin14to penetrate the recesses18, and joining the skin layer12and the core layer11in that state.

As a result, the matrix resin16of the skin layer12and the impregnating resin14of the core layer11are joined in a state in which some of the nonwoven fabric13and the impregnating resin14have penetrated the recesses18. That is, mixed regions20, in which the nonwoven fabric13and the fibers15are mixed, are formed in the joint portion19between the core layer11and the skin layer12. Thus, it is possible to enhance the joining force between the skin layer12and the core layer11and to reduce the possibility that the skin layer12and the core layer11will separate between the layers, even if a load is applied to the fiber-reinforced resin molding10.

Therefore, according to the method for producing a fiber-reinforced resin molding10of the present embodiment, it is possible to prevent the skin layer12from separating from the core layer11by increasing the joining force between the skin layer12and the core layer11.

(4) The recesses18are formed using a lost wax method.

Thus, it is possible to precisely form the recesses18on the skin layer12.

A method for producing a fiber-reinforced resin molding10according to another embodiment will be described with reference toFIG. 4.

1. Application of Wax

First, wax21is applied to a sheet or a bundle of fibers15, as illustrated inFIG. 4A, in randomly distributed fashion and the applied wax21is cured and hardened.

2. Injection of Matrix Resin into the Mold

Next, the fibers15are placed in the mold and the matrix resin16is injected into the mold to impregnate the fibers15with the matrix resin16, as illustrated inFIG. 4B. The impregnated matrix resin16is then cured and hardened to prepare the skin layer12.

3. Removal of the Wax

Next, the wax21is melted with warm water or a solvent to form recesses18on the skin layer12, as illustrated inFIG. 4C.

Next, a nonwoven fabric-containing adhesive (nonwoven fabric13that has been impregnated with impregnating resin14in advance) is stacked between a pair of skin layers12,12to prepare a stacked body23, as illustrated inFIG. 4D.

5. Forming the Fiber-Reinforced Resin Molding

Next, the stacked body23is placed in a mold, and a fiber-reinforced resin molding10is formed inside the mold, as illustrated inFIG. 4E. In this step to form the fiber-reinforced resin molding10in a mold, portions of the nonwoven fabric13and the impregnating resin14are made to penetrate each recess18, and the fibers15that are exposed due to the removal of the wax21become entangled with the nonwoven fabric13. The impregnating resin14is cured and hardened to prepare a fiber-reinforced resin molding10.

In this embodiment, a hot press molding method or an autoclave molding method may be used as the method for forming the fiber-reinforced resin molding10.

By using such a method for producing a fiber-reinforced resin molding10, it is possible to prevent the skin layer12from separating from the core layer11by increasing the joining force between the skin layer12and the core layer11.

The present invention was explained above in accordance with the embodiments, but the present invention is not limited by the foregoing descriptions, and it is obvious to a person skilled in the art that various modifications and improvements are possible.