Method for processing fiber-reinforced resin materials

A method for processing a fiber-reinforced resin material is disclosed. A fiber-reinforced resin material is disposed between an upper die having a projection and a lower die having a recess corresponding to the projection. The fiber-reinforced resin material includes reinforced fibers having alternately intersecting warp yarns and weft yarns and are impregnated with a thermoplastic resin. The fiber-reinforced resin material is then heated to soften the thermoplastic resin, and the upper die and the lower die are placed close to each other in order to insert the projection into a gap between the warp yarns and the weft yarns of the reinforced fibers such that the gap between the warp yarns and the weft yarns is expanded to form a through hole.

PRIORITY CLAIM

The present application claims benefit of priority under 35 U.S.C. §§ 120, 365 to the previously filed Japanese Patent Application No. JP2016-004640 with a priority date of Jan. 13, 2017, which is incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to fiber-reinforced resin materials in general, and in particular to a method for processing a fiber-reinforced resin material.

BACKGROUND

Chassis of electronic devices, such as laptop personal computers (laptop PCs), tablet personal computers (tablet Ps), smartphones, and cellular phones, need to be lightweight, thin and strong. In view of this, a fiber-reinforced resin, e.g., carbon fiber reinforced plastics (CFRP), in which reinforced fibers, e.g., carbon fibers, are impregnated with a resin has been widely employed for chassis of electronic devices.

For example, as shown inFIG. 10, in order to form a through hole31for screws or a through hole31A as air inlet/outlet in a fiber-reinforced resin material101, a technique known to-date includes a primary process of shaping a fiber-reinforced resin material101is performed, and then a secondary process of press-cutting with a press cutter, machining with a milling cutter, or cutting with a laser is performed. However, with the above-mentioned processing technique, the entire part of reinforced fibers10corresponding to through hole31or31A is cut off and removed in a hole forming step as illustrated inFIGS. 11-12, resulting in the problem of a decrease in strength of a region around the through hole31or31A.

Since the fiber-reinforced resin material is strong, press-cutting or machining can shorten the life of a tool, resulting in another problem of increased costs. In addition, since the fiber-reinforced resin material needs to be irradiated with high-power laser light for a long period in laser processing, the matrix resin around the through hole is burnt, resulting in yet another problem of a failure in forming a normal through hole.

Consequently, it would be preferable to provide an improved method for processing a fiber-reinforced resin material without a decrease in strength after processing, without an increase in costs, and without a degradation of processing accuracy.

SUMMARY

In accordance with an embodiment of the present disclosure, a fiber-reinforced resin material is disposed between an upper die having a projection and a lower die having a recess corresponding to the projection. The fiber-reinforced resin material includes reinforced fibers having alternately intersecting warp yarns and weft yarns and are impregnated with a thermoplastic resin. The fiber-reinforced resin material is then heated to soften the thermoplastic resin, and the upper die and the lower die are placed close to each other in order to insert the projection into a gap between the warp yarns and the weft yarns of the reinforced fibers such that the gap between the warp yarns and the weft yarns is expanded to form a through hole.

All features and advantages of the present disclosure will become apparent in the following detailed written description.

DETAILED DESCRIPTION

I. First Embodiment

A method for forming a through hole31or31A in a fiber-reinforced resin material1is illustrated inFIGS. 1-2. The fiber-reinforced resin material1to be processed in this embodiment is prepregs in which reinforced fibers10having a structure with alternately intersecting warp yarns11and weft yarns12(e.g., a woven structure) are impregnated with a matrix resin20. Specifically, the fiber-reinforced resin material1is a CFRP (a plate of laminated prepregs) in which prepregs are laminated to form a desired laminated structure or is in a state where prepregs are stacked to form a desired laminated structure. The reinforced fibers10are carbon fibers, and the matrix resin20is a thermoplastic resin. The through hole31or31A formed in the fiber-reinforced resin material1is used as a hole for screwing, an air inlet/outlet, a hole for a loudspeaker, and/or a hole for illumination, for example.

The method for processing a fiber-reinforced resin material according to this embodiment includes a disposing step and a through hole forming step. As illustrated inFIG. 3(a), the disposing step is a step of disposing a fiber-reinforced resin material1ayet to be processed in a die40including an upper die41and a lower die42. Specifically, in the disposing step, the upper die41having a projection41aand the lower die42having a recess42acorresponding to the projection41aare prepared, and the fiber-reinforced resin material1ais disposed between the upper die41and the lower die42.

Here, the projection41aof the upper die41is used for forming a through hole31or31A in the fiber-reinforced resin material1ain the subsequent through hole forming step. As illustrated inFIGS. 3(a)-3(c), the projection41ahas a tapered cross-sectional shape that gradually narrows toward the lower die42. A plane shape of the projection41awhen viewed from the lower die42corresponds to a plane shape of the through hole31or31A formed in the through hole forming step.

For example, as illustrated inFIG. 1, in the case of forming the circular through hole31in the fiber-reinforced resin material1a, the projection41ahas a circular plane shape when viewed from the lower die42. The overall shape of the projection41ain this case is, for example, a conical shape having a circular bottom. On the other hand, as illustrated inFIG. 2, in the case of forming the oval through hole31A in the fiber-reinforced resin material1a, the projection41ahas a rounded rectangle or oval plane shape when viewed from the lower die42. The overall shape of the projection41ain this case is, for example, a quadrangular pyramid shape having a rounded rectangular bottom.

Next, the through hole forming step is a step of forming the through hole31or31A in the fiber-reinforced resin material1a. In the through hole forming step, the fiber-reinforced resin material1ais heated by using contact heat transfer caused by heating the die40, for example, or by an unillustrated heater or the like, thereby melting and softening the thermoplastic resin (matrix resin20). In the state where the thermoplastic resin of the fiber-reinforced resin material1ais melted and softened in the manner described above, the upper die41and the lower die42are placed close to each other as illustrated inFIG. 3(b)so that the fiber-reinforced resin material1ais subjected to hot pressing.

In the through hole forming step, concurrently with hot pressing of the fiber-reinforced resin material1a, the projection41ais inserted into the fiber-reinforced resin material1a, as illustrated inFIG. 3(b), thereby forming a through hole31or31A, as illustrated inFIG. 3(c). In the through hole forming step, when forming the through hole31or31A, the projection41ais inserted into a weave pattern13formed by the warp yarns11and the weft yarns12of the reinforced fibers10as illustrated inFIGS. 1 and 2, thereby forming a through hole31or31A by expanding the weave pattern13. In this manner, in the through hole forming step, the through hole31or31A is formed in a state where the matrix resin20of the fiber-reinforced resin material1aafter processing is melted and softened. The “weave pattern” here refers to a gap between the warp yarns11and the weft yarns12of the reinforced fibers10.

As illustrated inFIGS. 1-2, the fiber-reinforced resin material1processed by the method for processing a fiber-reinforced resin material according to this embodiment has the through hole31or31A formed in the thickness direction thereof. The through hole31or31A is not formed by cutting and removing the reinforced fibers10, unlike a known technique, but by expanding the weave pattern13of the reinforced fibers10(by pushing away the reinforced fibers10) in directions (warp and weft directions) orthogonal to the thickness direction.

Thus, in the processed fiber-reinforced resin material1, the density of a part of the reinforced fibers10around the through hole31or31A is higher than the density of the other part in the directions orthogonal to the thickness direction. That is, the reinforced fibers10that have been pushed away in forming the through hole31or31A are densely arranged around the through hole31or31A so that gaps between the warp yarns11and gaps between the weft yarns12in a region around the through hole31or31A are narrower than gaps between the warp yarns11and gaps between the weft yarns12in the other region. Accordingly, the region around the through hole31or31A is reinforced by the reinforced fibers10so that a decrease in strength of the region around the through hole31or31A can be suppressed.

With the method for processing a fiber-reinforced resin material according to this embodiment, the through hole31or31A is formed not by cutting and removing the reinforced fibers10but by expanding the weave pattern13between the warp yarns11and the weft yarns12of the reinforced fibers10. Thus, the fiber-reinforced resin material1can be processed without increases in costs and a processing period and degradation of processing accuracy, which have occurred in a known processing method. In addition, in the method for processing a fiber-reinforced resin material according to this embodiment, the thermoplastic resin that is melted and softened by heat is used as the matrix resin20. Thus, concurrently with formation of the through hole31or31A in the through hole forming step, the fiber-reinforced resin material1can be formed in a desired shape by hot press forging.

II. Second Embodiment

The method for processing a fiber-reinforced resin material according to the second embodiment is similar to the method of the first embodiment except for using a thermosetting resin as a matrix resin20. A fiber-reinforced resin material1to be processed in the second embodiment is prepregs in which reinforced fibers10having a structure with alternately intersecting warp yarns11and weft yarns12(e.g., a woven structure) are impregnated with the matrix resin20, as in the first embodiment. The fiber-reinforced resin material1is, for example, in a state where prepregs are laminated to form a desired laminated structure, the reinforced fibers10are carbon fibers, and the matrix resin20is a thermosetting resin.

The method for processing a fiber-reinforced resin material according to the second embodiment includes a disposing step and a through hole forming step. As illustrated inFIG. 3(a), in the disposing step, a fiber-reinforced resin material1ain which the reinforced fibers10are impregnated with a thermosetting resin (matrix resin20) yet to be cured is disposed between an upper die41having a projection41aand a lower die42having a recess42acorresponding to the projection41a. Specifically, in the disposing step of the first embodiment, the processed fiber-reinforced resin material1aincluding the cured thermoplastic resin is disposed in the die40, whereas in the disposing step of the second embodiment, the fiber-reinforced resin material1athat includes an uncured thermosetting resin and has not been shaped yet is disposed in the die40. The upper die41and the lower die42in the second embodiment are similar to those used in the first embodiment.

Subsequently, in the through hole forming step, before the thermosetting resin (matrix resin20) is completely cured, the upper die41and the lower die42are placed close to each other so that as illustrated inFIGS. 1-2, the projection41ais inserted into the weave pattern13formed by the warp yarns11and the weft yarns12of the reinforced fibers10, thereby forming the through hole31or31A by expanding the weave pattern13. In the through hole forming step of the second embodiment, the through hole31or31A can be formed by using any one of hot pressing or cold pressing.

In the case of using hot pressing, in a manner similar to the first embodiment, in a state where the fiber-reinforced resin material1ais heated and the thermosetting resin (matrix resin20) is not completely cured, the upper die41and the lower die42are placed close to each other, as illustrated inFIG. 3(b)and the fiber-reinforced resin material1ais subjected to hot pressing. In this manner, the projection41apenetrates the fiber-reinforced resin material1aso that the through hole31or31A, as illustrated inFIG. 3(c), is formed and the fiber-reinforced resin material1ais shaped.

On the other hand, in the case of using cold pressing, prepregs are disposed in the die40to form a desired laminated structure, and then, the upper die41and the lower die42are placed close to each other, and the fiber-reinforced resin material1ais subjected to cold pressing. Subsequently, the die40is heated, for example, so that the fiber-reinforced resin material1ais cured by heat. In this manner, the projection41apenetrates the fiber-reinforced resin material1aso that the through hole31or31A, as illustrated inFIG. 3(c)is formed and the fiber-reinforced resin material1ais shaped.

The fiber-reinforced resin material1processed by the method for processing a fiber-reinforced resin material according to this embodiment includes the through hole31or31A formed by expanding the weave pattern13between the warp yarns11and the weft yarns12of the reinforced fibers10(by pushing the reinforced fibers10) in directions orthogonal to the thickness direction (warp and weft directions), as illustrated inFIGS. 1-2.

Thus, in the processed fiber-reinforced resin material1, the density of a part of the reinforced fibers10around the through hole31or31A is higher than the density of the other part in the directions orthogonal to the thickness direction, and gaps between the warp yarns11and gaps between the weft yarns12in a region around the through hole31or31A are narrower than gaps between the warp yarns11and gaps between the weft yarns12in the other region. Accordingly, the region around the through hole31or31A is reinforced by the reinforced fibers10so that a decrease in strength of the region around the through hole31or31A can be suppressed.

The method for processing a fiber-reinforced resin material according to the second embodiment can process the fiber-reinforced resin material1without increases in costs and a processing period and degradation of processing accuracy. Since the method for processing a fiber-reinforced resin material according to the second embodiment uses a thermosetting resin that is cured by heat as the matrix resin20, the through hole31or31A can be formed concurrently with shaping of the fiber-reinforced resin material1in the through hole forming step.

III. Other Embodiments

In the through hole forming step of each of the first and second embodiments described above, it can be difficult to push the entire part of the reinforced fibers10corresponding to the through hole31or31A with some sizes or aspect ratios of the through hole31or31A to be formed. In such a case, a cutting step is preferably performed before the disposing step.

As illustrated inFIGS. 4-5, in the cutting step, a part of the reinforced fibers10in a region where the through hole31or31A is to be formed in the through hole forming step is cut off. A method for processing a fiber-reinforced resin material including the cutting step will now be described.

First, the reinforced fibers10are impregnated with the matrix resin20, thereby preparing prepregs. Subsequently, as the cutting step, a part of the reinforced fibers10constituting the prepregs and included in a region A or B where the through hole31or31A is to be formed is cut off. Thereafter, the prepregs that have been cut off are laminated to form a desired laminated structure. Here, in a case where the matrix resin20is a thermoplastic resin, the laminated prepregs may be subjected to hot pressing so that a plate of laminated prepregs (fiber-reinforced resin material1a) is formed. Lastly, the through hole forming step according to the first or second embodiment is performed, thereby forming a through hole31or31A.

Here, as illustrated inFIG. 4, for example, in the case of forming the circular through hole31in the subsequent through hole forming step, in the cutting step, the reinforced fibers10(the warp yarns11and the weft yarns12) are cut off in the warp and weft directions with respect to a center of the region A where the through hole31is to be formed, thereby forming cross-shaped slits C1. The lengths of the slits C1, that is, the numbers of warp yarns11and weft yarns12to be cut off are determined in consideration of the size of the through hole31to be formed.

The shape of the slits C1for forming the circular through hole31is not limited to the cross-shape, and only some of the reinforced fibers10(weft yarns12), for example, may be cut off in the warp direction or only some of the reinforced fibers10(warp yarns11) may be cut off in the weft direction.

In addition, as illustrated inFIG. 5, for example, in the case of forming the oval through hole31A elongated in the warp direction in the subsequent through hole forming step, in the cutting step, the reinforced fibers10(weft yarns12) are cut off in the warp direction with respect to the center of the region B where the through hole31A is to be formed, thereby forming a linear slit C2. The length of the slit C2, that is, the number of weft yarns12to be cut off, is determined in consideration of the size of the through hole31A to be formed.

In the case of forming the oval through hole31A, the slit C2is preferably formed only in the direction parallel to the direction in which the through hole31A extends. For example, as illustrated inFIG. 5, in the case of forming the oval through hole31A elongated in the warp direction in the subsequent through hole forming step, only a part of the weft yarns12intersecting the warp direction along which the oval through hole31A extends is cut off and the warp yarns11are not cut off. In this manner, a decrease in strength caused by cutting the reinforced fibers10in the cutting step can be minimized.

The cutting step as described above included in the method for processing a fiber-reinforced resin material according to the first or second embodiment can ensure formation of the through hole31or31A by pushing away the reinforced fibers10in the subsequent through hole forming step, irrespective of the size and aspect ratio of the through hole31or31A to be formed. In the cutting step, only a minimum part of the reinforced fibers10is cut off and is not removed. Thus, after formation of the through hole31or31A in the through hole forming step, a part of the reinforced fibers10that has been cut off in the cutting step is disposed around the through hole31or31A together with a part of the reinforced fibers10that has been pushed away, and also contributes to enhancement of strength of a region around the through hole31or31A.

In the through hole forming step in the first or second embodiment, only the through hole31or31A is formed as processing on the fiber-reinforced resin material1. Alternatively, a rib and/or a boss, for example, can be formed concurrently with formation of the through hole31or31A.

In the case of forming a rib32concurrently with formation of the through hole31or31A, for example, as illustrated inFIG. 6, a die40A different from the die40used in the methods for processing a fiber-reinforced resin material according to the first and second embodiments is used. The die40A includes an upper die41and a lower die42A, and the upper die41is similar to the upper die used in the methods for processing a fiber-reinforced resin material according to the first and second embodiments. On the other hand, the lower die42A has a first recess42band a second recess42cdisposed above the first recess42band having an opening larger than an opening of the first recess42b.

In the disposing step, as illustrated inFIG. 6(a), a fiber-reinforced resin material1ais disposed between the upper die41having a projection41aand the lower die42A having the first recess42band the second recess42c. Subsequently, in the through hole forming step, the fiber-reinforced resin material1ais heated so that the thermoplastic resin is melted and softened (in the first embodiment) or the thermosetting resin is cured (in the second embodiment), and the fiber-reinforced resin material1ais subjected to hot pressing as illustrated inFIG. 6(b).

In the through hole forming step, concurrently with the hot pressing of the fiber-reinforced resin material1a, the projection41ais inserted into a weave pattern13formed by warp yarns11and weft yarns12of the reinforced fibers10as illustrated inFIGS. 1, 2, and 6(b), thereby forming a through hole31or31A by expanding the weave pattern13. At the same time, the matrix resin20(the thermoplastic resin or the thermosetting resin) is caused to flow into the second recess42cso that as illustrated inFIGS. 6(c)and7, a rib32is formed to project in the thickness direction from a region around the through hole31or31A.

As illustrated inFIG. 7, a part of the reinforced fibers10that has been pushed away in forming the through hole31or31A is basically disposed around the through hole31or31A. Thus, most part of the rib32is constituted by the matrix resin20, and the density of the part of the reinforced fibers10constituting the rib32is lower than the density of the other part, that is, a part of the fiber-reinforced resin material1A except for the rib32.

The through hole forming step performed by the method for processing a fiber-reinforced resin material according to the first or second embodiment enables a plurality of processes to be performed at the same time. In addition, since the matrix resin20can escape into the second recess42cin forming the through hole31or31A, the through hole31or31A can be easily formed. Furthermore, since the rib32is formed around the through hole31or31A, the rib32can reinforce a region around the through hole31or31A so that a decrease in strength of the region around the through hole31or31A can be further suppressed.

The fiber-reinforced resin material1processed by the processing method as described above can be used for a chassis of a laptop PC50as illustrated inFIG. 8, for example. The laptop PC50illustrated inFIG. 8is of a clamshell type including a device body51including a keyboard device511, and a rectangular plate-shaped lid52including a display device521of, for example, a liquid crystal display, and the lid52is coupled to the device body51by left and right hinges522to be freely opened and closed. The device body51houses unillustrated electronic components such as a substrate, an arithmetic processing unit, a hard disk device, and a memory.

The use of the method for processing a fiber-reinforced resin material according to the first or second embodiment enables easy formation of the through hole31as a hole for screwing or the through hole31A as an air inlet/outlet in a rear cover512of the device body51as illustrated inFIG. 9, for example.

As described above, methods for processing a fiber-reinforced resin material and fiber-reinforced resin materials according to embodiments of the present invention have been specifically described. The present invention, however, is not limited to the above description, and should be widely understood based on claims. Various changes and modifications, for example, based on the description are, of course, included in the gist of the present invention.

For example, the reinforced fibers10are not limited to carbon fibers, and may be metal fibers or vegetable fibers, for example. The reinforced fibers10may not have a woven structure as illustrated inFIGS. 1-2, and may have a structure in which prepregs of a uni-direction (UD) material where fibers run in one direction are stacked in warp and weft directions, for example. In such a structure, a gap between warp fibers and weft fibers is expanded by the projection41aof the upper die41so that the through hole31or31A can be formed. The reinforced fibers10may not have a woven structure as illustrated inFIGS. 1-2, and may have a structure in which nonwoven prepregs of entangled fibers are laminated.

As has been described, the present invention provides an improved method for processing a fiber-reinforced resin material.