Method for rtm molding

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to an RTM (Resin Transfer Molding) molding method for an FRP (fiber reinforced plastic) structure, and more particularly to an RTM molding method capable of preventing partial resin flow failure and impregnation failure in a mold cavity. ..

【0002】

[Conventional technology]

Conventionally, as a method of molding an FRP structure, a reinforcing fiber base material is placed in a closed cavity formed by a mold, and a resin is pressure-injected into the cavity to forcibly fill the cavity. At the same time, there is known an RTM molding method in which a reinforcing fiber base material is impregnated and the resin is cured by heating or the like to form an FRP.

【0003】

In this conventional RTM molding method, particularly when the cavity is formed into a complicated shape with irregularities, there may be a portion in the cavity where the resin does not flow well. Further, even if the resin is pressure-injected into the reinforcing fiber base material filled with high density, if there is a portion having a high flow resistance, it may be difficult to flow the resin well in that portion. is there.

【0004】

If it is difficult for the resin to flow in the cavity or if there is a part where the resin does not flow in, poor resin impregnation may occur, or air bubbles may be entrained because the air bubbles are not pushed out, resulting in defects such as deficiency and voids. Sometimes. In particular, the presence of such defects on the design side is fatal to the quality of FRP products. In addition, when a resin deficiency occurs, the strength is partially insufficient, which also causes a structural defect. Such defects are particularly likely to occur in the recesses of the mold forming the cavity, particularly in the corners of the recesses and in the vicinity of the resin injection port into the cavity.

【0005】

It is conceivable to increase the injection pressure of the resin in order to prevent the occurrence of the above-mentioned defects, but if the pressing pressure of the resin is increased, the fiber orientation of the reinforcing fiber base material arranged in the cavity is disturbed, and the fiber orientation is disturbed. It will cause a decrease in the strength of that part.

【0006】

[Problems to be Solved by the Invention]

Therefore, the subject of the present invention is to pay attention to the above-mentioned problems, to enable the resin to flow satisfactorily even in a portion in the cavity where a problem is likely to occur in the resin flow, without increasing the resin injection pressure, and to make the resin flow satisfactorily as a whole. It is an object of the present invention to provide an RTM molding method capable of obtaining a defect-free FRP structure.

【0007】

[Means for solving problems]

In order to solve the above problems, the RTM molding method according to the present invention is a RTM molding method in which a reinforcing fiber base material is placed in a cavity formed by a mold, a resin is injected into the cavity, and then the resin is cured. It comprises a method characterized by arranging a medium for diffusing the injected resin in at least a part of the inside.

【0008】

In this RTM molding method, only the above medium can be placed in a portion where the resin has been difficult to flow in the past, or a release material (peel ply) can be placed together with the medium. When the release material is placed, the medium and the release material can be removed from the molded FRP structure after demolding.

【0009】

The medium for diffusing the resin in the present invention is not particularly limited as long as the injected resin can be diffused through the medium. For example, a woven fabric or knitted fabric capable of forming a resin guide flow path, a sheet made of a porous body, a sheet having a large number of grooves formed or the like can be used, and the woven fabric or knitted fabric is particularly preferable. As the material of the woven fabric or knitted fabric constituting the medium, for example, polyester or polypropylene can be used.

【0010】

Further, the mold release material in the present invention is not particularly limited as long as it can be easily peeled off and removed after molding, but since it is provided together with the above medium, at least a material that does not impair the resin diffusion function of the medium is preferable. As such a mold release material, for example, a nylon or polyester mold release woven fabric can be used.

【0011】

Further, in the RTM molding method according to the present invention, it is preferable to reduce the pressure inside the cavity by vacuum suction and maintain the reduced pressure state before injecting the resin. Since the inside of the cavity is usually sealed, by reducing the pressure inside the cavity, the differential pressure from the inside of the cavity can be increased without increasing the resin injection pressure so much, and the resin flows in the cavity. Not only is it easier, but bubbles are less likely to remain.

【0012】

Further, in the RTM molding method according to the present invention, a resin outlet that can be opened and closed is provided at a position away from the resin injection port into the cavity, and at least a part of the injected resin is introduced from the resin injection port into the cavity. It is preferable to allow the resin to flow toward the resin outlet through the reinforcing fiber base material arranged in the above and through the medium arrangement portion. With this configuration, a flow path through which the resin flows relatively easily is intentionally formed, and the resin is intentionally flowed along the flow path. The resin can be flowed to the surface, and the resin can be satisfactorily diffused at the site by the above medium.

【0013】

In the present invention, the medium for diffusion of the resin is arranged at a portion where the resin is difficult to flow and defects are likely to occur, especially in the conventional RTM molding method. For example, it is effective to arrange the cavity forming portion of the mold in a recess, particularly a portion including a corner portion of the recess. It is also effective to dispose the medium in a portion of the cavity including the resin injection port.

【0014】

In the RTM molding method according to the present invention as described above, by partially arranging the medium in the cavity, the resin can be applied along the medium even in a portion where defects such as deficiencies and voids are likely to occur in the past. It enables good diffusion and allows the formation of an overall defect-free FRP structure.

【0015】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, desirable embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an RTM molding method according to an embodiment of the present invention. In FIG. 1, 1 indicates a mold, and a cavity 2 having an uneven shape is formed inside by molding the upper mold 1a and the lower mold 1b. In the cavity 2, the reinforcing fiber base material 3 is arranged in a predetermined form during RTM molding of FRP. The form of the reinforcing fiber base material 3 is not particularly limited, and a reinforcing fiber woven fabric, a unidirectional reinforcing fiber, a combination thereof, a plurality of layers arranged, a mat or the like, or the like can be used. The type of the reinforcing fiber is not particularly limited, and reinforcing fibers for FRP molding, for example, carbon fibers, glass fibers, aramid fibers, and the like, and inorganic fibers can also be used.

【0016】

Resin is injected into the cavity 2 through the resin injection port 4 from the central portion of the mold 1 and from the upper mold 1a side in this embodiment. This resin injection is performed by pressurization, but in the present invention, the resin is well diffused even in the inner part of the cavity 2 where the resin has been difficult to flow in the past, so it is not necessary to increase the pressing force so much. ~ 2kg / cm²Degree is enough. In particular, if the inside of the cavity 2 is kept under reduced pressure by vacuum suction before resin injection, the injection pressure can be further reduced. The injection resin is not particularly limited, and any resin that can be used as a matrix resin for FRP can be used, and a thermoplastic resin can be used in addition to a thermosetting resin. In particular, examples of the thermosetting resin include epoxy resin, unsaturated polyester resin, phenol resin, vinyl ester resin and the like.

【0017】

Further, in the embodiment shown in FIG. 1, only the reinforcing fiber base material 3 is arranged in the cavity 2 before the resin is injected, but if necessary, an FRP integrally molded member such as a core material is arranged. You may. When arranging the core material, it is also possible to arrange the reinforcing fiber base material on both sides of the core material in between to form a sandwich structure.

【0018】

A resin outlet 6 provided with a cock 5 that can be opened and closed is provided at a position away from the resin injection port 4. The resin outlet 6 may be arranged at a portion immediately before the sealing material 7 provided around the cavity 2. Further, a plurality of resin outlets 6 can be provided. For example, a plurality of resin flow paths from the resin inlet 4 to the resin outlet 6 are arranged around the resin inlet 4 so as to be formed as uniformly as possible. can do. At the time of resin injection, the cock 5 may be opened first, and the cock 5 may be closed when the resin flowing in the cavity 2 starts to flow out from the resin outlet 6. After closing the cock 5, the static pressure of the resin fills the cavity 2 with the resin, and the inside of the cavity 2 is pressurized (for example, 1 to 2 kg / cm described above).²In the case of thermosetting resin, it is cured by heating.

【0019】

In the cavity 2 formed as described above, a medium for resin diffusion is partially arranged in a portion where the resin has been difficult to flow in the past. In the example shown in FIG. 1, the medium 9 is arranged in the recess 8 for forming the cavity of the lower mold 1b, particularly in the portion including the corner portion of the recess 8, and the resin injection port 4 is opened into the cavity 2. The medium 10 is arranged in a portion including the portion. The medium may be selectively and partially arranged in a portion where defects such as deficiency and voids are likely to occur in the past, and in the example of FIG. 1, either the medium 9 or the medium 10 may be used. it can.

【0020】

As the medium 9 and the medium 10, those having a guide flow path of the resin and capable of diffusing the resin are preferable, and for example, a woven fabric or a knitted fabric having a size of about # 50 to 200 mesh as shown in FIG. 2 may be used. preferable. The material is not particularly limited, and as described above, a woven fabric or knitted fabric made of polyester or polypropylene can be used.

【0021】

Further, although not shown, a release material called a so-called peel ply can be arranged together with the medium 9 and the medium 10. If such a peel ply is arranged, the peel ply and the medium can be easily removed after FRP molding and demolding.

【0022】

In the above RTM molding method, the resin is pressurized (1 to 2 kg / cm).²(Degree), it is injected into the cavity 2 as a closed space, and the reinforcing fiber base material 3 arranged in the cavity 2 is impregnated. The resin flows in the cavity 2, but it becomes difficult for the resin to flow in the portion where the resistance due to the reinforcing fiber base material 3 is high, the recess 8, and the corner portion thereof. However, since the medium 9 and the medium 10 are arranged in such a portion where the flow is difficult, the resin is guided along the medium 9 and the medium 10 and diffuses well in a state where the flow resistance is small. Therefore, even in these parts, there is no possibility that an amount of deficiency or voids will occur, and the occurrence of defects in terms of appearance and strength can be prevented. When one surface of the FRP structure to be molded is formed on the design surface, it is preferable that the medium 9 and the medium 10 are arranged on the anti-design surface. Further, if the medium 9 and the medium 10 are integrally molded without any problem, they can be left as they are, and if there is a problem, they can be easily removed after molding by arranging them together with the peel ply as described above. ..

【0023】

In addition, the flow resistance in the vicinity of the resin injection port 4 is higher than that in other parts, the resin does not flow easily, it takes a long time for the resin to wrap around the entire cavity 2, and the resin reaches the pot life and gels. May cause voids. However, by arranging the medium 10 in this portion, the resin easily flows in and flows easily into the cavity 2, so that the occurrence of defects in this portion is effectively prevented.

【0024】

Further, if the resin outlet 6 is appropriately arranged, it becomes possible to intentionally form a flow path through which the resin easily flows from the resin inlet 4 to the resin outlet 6, and the resin flow is intentional. It becomes possible to give directionality to. In particular, if the medium 9 is placed in a portion where the conventional resin is difficult to flow and the directivity of the resin flow is provided in the direction in which the conventional resin is difficult to flow, a sufficient amount of resin can be flowed in the portion. At the same time, the flowing resin can be diffused uniformly and satisfactorily. As a result, the occurrence of deficiency and voids is surely prevented.

【0025】

Further, by keeping the inside of the sealed cavity 2 in a reduced pressure state before injecting the resin as described above, the differential pressure between the injection pressure and the pressure inside the cavity becomes large, and the resin becomes easier to flow. In addition, the resin injection pressure can be reduced. As a result, the resin can be reliably and evenly diffused without disturbing the orientation of the reinforcing fibers of the reinforcing fiber base material 3. Further, the reduced pressure makes it difficult for bubbles to be generated, and the occurrence of void defects is more reliably prevented.

【0026】

As described above, since the RTM molding method according to the present invention can perform FRP molding in which the generation of shortages and voids is prevented, various types of products manufactured by this molding method have strict requirements for surface quality. The present invention can be suitably applied to automobile parts such as bonnets (hoods), roofs, fenders, bumpers, trunk lids, doors and the like.

【0027】

[Effect of the invention]

As described above, according to the RTM molding method of the present invention, by partially arranging the medium in the cavity, the resin can be satisfactorily spread over the entire cavity without increasing the resin injection pressure. It becomes possible to make it flow, and it is possible to easily form an FRP structure of excellent quality without defects such as deficiencies and voids as a whole. Therefore, this RTM molding method can be applied as a method for manufacturing automobile parts, which have strict requirements for surface quality.

[Simple explanation of drawings]

[Figure 1]

It is a partial sectional view of the molding apparatus for carrying out the RTM molding method which concerns on one Embodiment of this invention.

[Figure 2]

It is the schematic perspective view which shows an example of the medium used for the method of FIG.

[Explanation of symbols]

1 mold 1a upper mold 1b lower mold 2 cavities 3 Reinforcing fiber base material 4 Resin inlet 5 cock 6 Resin outlet 7 Sealing material 8 recess 9, 10 media