JP2008246981A - Manufacturing method of fiber-reinforced composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a surface smoothness of a good SMC molded article by a further simple and cheap method. <P>SOLUTION: A carbon fiber is impregnated with an unsaturated polyester resin to form a sheet-like CFRP substrate (prepreg). Subsequently, a resin non-impregnated nonwoven fabric is interposed between CFRP layers to form a prepreg laminate, and predetermined pressurizing power is given to the prepreg laminate by a forming die. The SMC molded article is obtained by the pressure forming. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a fiber-reinforced composite material such as FRP, for example.

  Conventionally, a method of manufacturing an FRP (Fiber Reinforced Plastics) molded product by press molding an SMC (Sheet Molding Compound) molding material is known.

  In this FRP molded product, unevenness may occur on the surface of the FRP molded product due to a mixture of shrinkable matrix resin and non-shrinkable reinforcing fibers and inorganic particles such as calcium carbonate.

  For example, in an FRP molded product that requires excellent appearance quality, such as an exterior part of an automobile, various smoothing means for smoothing irregularities generated on the surface of the FRP molded product are used. In general, as a pre-treatment for press molding, a method of applying a gel coat coating or the like on the surface side of a mold that requires appearance performance in advance during press molding, or in-mold on the surface side of an intermediate molded body that requires appearance performance Examples thereof include a method of performing a coating treatment, and a method of smoothing surface irregularities generated after molding by a polishing means such as sandpaper.

In addition, as a method for smoothing the surface of an FRP molded product, for example, Patent Document 1 discloses the production of a resin composition for a fiber-reinforced composite material in which inorganic particles are dispersed in advance in a part of an epoxy resin in an epoxy resin composition. A method is disclosed. In Patent Document 2, there is a method for smoothing the surface by mixing two types of reinforcing fibers of about 1 inch in length and about 1/2 inch in length as reinforcing fibers. It is disclosed.
JP 11-35794 A (paragraphs 0008 to 0010) Japanese Patent Laying-Open No. 2005-2288 (paragraphs 0010 to 0012)

  As a method of obtaining surface smoothness in an SMC molded product, in Patent Document 1, a method of reducing the amount of molding shrinkage by improving the composition of an epoxy resin that is a matrix resin is adopted. In Patent Document 2, strengthening is performed. A method of reducing the amount of surface irregularities by improving the shape of the fiber itself has been adopted.

  However, in the technical idea disclosed in Patent Document 1 and Patent Document 2, the molding process is complicated in order to modify the matrix resin or the reinforcing fiber. Further, in the industry, there is a demand for improving the surface smoothness of SMC molded products by a method that is much simpler and cheaper than the surface smoothing methods disclosed in Patent Document 1 and Patent Document 2. ing.

  The present invention has been made in view of the above points, and provides a method for producing a fiber-reinforced composite material capable of obtaining good surface smoothness of an SMC molded article by a more simple and inexpensive method. For the purpose.

  In the present invention, first, a reinforcing fiber material is impregnated with a resin to form a sheet-like prepreg. Subsequently, when a plurality of the prepregs are laminated and molded by a molding die, a prepreg laminate is formed between the prepreg layers by interposing a substrate not impregnated with resin, and a pressure is applied to the prepreg laminate. Apply and pressure mold. Further, after the pressure-molded prepreg laminate is impregnated with a resin, the molded product is obtained by curing the resin.

  Here, the “prepreg” refers to a mat-shaped base material obtained by cutting carbon fiber, aramid fiber, glass fiber, vinylon fiber, etc. from 1/2 inch to 4 inch to obtain a chop shape, or a nonwoven fabric or fiber. Refers to a sheet body in an uncured state in which various thermosetting resins (matrix resins) are impregnated with respect to a material (fiber reinforcing material) aligned in one direction.

  Examples of the matrix resin include unsaturated polyester resins, phenol resins, and epoxy resins.

  In the present invention, the non-impregnated base material interposed between the prepreg layers may be any substrate that is not impregnated with resin, and may be, for example, a nonwoven fabric or a woven fabric.

  The said nonwoven fabric means things other than textile fabrics, such as a mat | matte, a nonwoven fabric, and paper, for example.

  According to the present invention, the base material not impregnated with the resin is interposed between the prepreg layers, and the thickness direction of the obtained molded product is subdivided (divided) by the base material not impregnated with the resin. Thereby, shrinkage of the resin in the thickness direction can be suppressed.

  Furthermore, according to the present invention, by sandwiching both surfaces (laminated surfaces) of the laminated prepregs with an unimpregnated base material, the swell of reinforcing fibers due to the fluidity of the resin is suppressed, and the surface of the molded product is suppressed. Surface unevenness can be achieved by suppressing the occurrence of unevenness.

  As described above, in the present invention, the resin-impregnated base material is interposed between the prepreg layers, thereby suppressing depression due to shrinkage of the resin contained in the prepreg layer by the non-impregnated base material and the resin. It is possible to suppress the undulation of the reinforcing fiber due to the plastic flow. As a result, according to the present invention, it is possible to obtain a molded product having a good appearance quality that is suppressed from being depressed on the surface of the molded product and smoothed.

  In the present invention, an effect that a good SMC molded article having surface smoothness can be obtained by a more simple and inexpensive method in which an unimpregnated base material is interposed between prepreg layers. Play.

  In the present invention, for example, glass fiber, carbon fiber, aramid fiber, boron fiber, alumina fiber, silicon carbide fiber or the like is used as the “reinforced fiber material”. Two or more of these fibers may be mixed and used. Moreover, it does not specifically limit about the form and arrangement | sequence of a reinforced fiber. In order to reduce the weight and improve the durability, it is particularly preferable to use carbon fibers.

  As a method for producing the prepreg of the present invention, for example, for a thermosetting resin, a wet method in which a matrix resin is dissolved in a solvent to lower the viscosity and impregnated, and for a thermoplastic resin, a heating method is used. And a hot melt method in which the viscosity is lowered by impregnation.

  Furthermore, examples of the method for molding the prepreg laminate of the present invention include press molding using a molding die, but vacuum bag molding, autoclave molding using a vacuum bag, and the like may be applied.

  Further, in the present invention, the non-impregnated base material interposed between the prepreg layers may be any material that is not impregnated with a resin, for example, any of a nonwoven fabric or a woven fabric, Any material that is not impregnated with resin, such as glass fiber or carbon fiber, may be used.

  In this embodiment, as shown in FIG. 1, an upper die provided with a punch for applying pressure to the SMC molding material, and a cavity and rib for placing (laying) the SMC molding material are formed. A press mold composed of a lower mold having rib forming recesses was prepared, and a predetermined pressure was applied to the SMC molding material by the punch to obtain an SMC molded product.

  This SMC molding material comprises a CFRP base material (prepreg) comprising a sheet body in an uncured state by impregnating an unsaturated polyester resin into a mat base material obtained by making a 1-inch chopped carbon fiber, and the unsaturated base material. A laminate was formed by alternately laminating non-impregnated non-impregnated nonwoven fabrics such as polyester resin. In this case, since the CFRP substrate is in an uncured state, the nonwoven fabric is harder than the CFRP substrate.

  Specifically, three CFRP base materials composed of a sheet body obtained by impregnating an unsaturated polyester resin into a mat base material obtained by chopping carbon fibers into one inch, and the unsaturated polyester resin or the like And three nonwoven fabrics not impregnated with resin. First, a first CFRP base material is laid on the bottom layer of the cavity bottom wall in which the rib forming recesses are formed, and the first CFRP base material is Laminating a first non-woven fabric on the upper surface, subsequently laying a second CFRP substrate on the upper surface of the first non-woven fabric, laminating a second non-woven fabric on the upper surface of the second CFRP substrate, and A third CFRP base material was laid on the upper surface of the second nonwoven fabric, and a third nonwoven fabric was sequentially laminated on the upper surface of the third CFRP base material to form a laminate.

  In this way, the first and third CFRP substrates and the first to third nonwoven fabrics are sandwiched between the first and third nonwoven fabrics of the second and third CFRP substrates, respectively. The prepreg laminated body comprised by this was formed. In addition, after constructing in advance a laminated body in which the first to third CFRP base materials and the first to third nonwoven fabrics are sequentially superimposed by the above-described method, the laminate may be transferred into the lower mold cavity. .

  FIG. 2A is a partially enlarged longitudinal sectional view of an SMC molded product after a pressing force is applied by a punch to the SMC molding material molded according to the present embodiment, and FIG. It is a characteristic view which shows the surface roughness of the surface (uppermost surface of a laminated body) of the said SMC molded product shape | molded by the present Example. The surface roughness was measured based on JIS standard B-0601.

  In FIG. 2A, the white portions extending along the substantially horizontal direction indicate nonwoven fabrics impregnated with resin by press molding. In this example, the shrinkage of the resin in the thickness direction could be suppressed by subdividing (dividing) the thickness direction (vertical direction) of the SMC molded product with a non-impregnated nonwoven fabric.

  In other words, in this example, the thickness direction of the CFRP base material that is a prepreg is continuously sandwiched in the thickness direction of the SMC molded product by sandwiching the non-impregnated resin with a nonwoven fabric that is harder than the CFRP base material. The resin-rich portion to be removed can be eliminated, and the surface smoothing can be achieved by suppressing the generation of the depression (concave portion) due to the resin shrinkage on the surface side (the uppermost surface of the laminate) of the SMC molded product. As a result, in this example, it was possible to obtain an SMC molded product with good appearance quality.

  Furthermore, when a pressing force is applied to the prepreg laminate from above, it is assumed that the carbon fiber contained in the CFRP base material is shaped while being swelled by plastic flow under the action of the pressing force. In this example, by sandwiching the upper and lower surfaces of the CFRP base material, which is a prepreg, with the nonwoven fabric, the undulation of the carbon fiber due to fluidity is suppressed, and the undulation of the carbon fiber on the surface side of the SMC molded product is suppressed. It was possible to achieve surface smoothing by suppressing the occurrence of surface irregularities.

  About this point, while the resin layer (CFRP base material layer) shown by the black part in FIG. 2 (a) is extending substantially horizontally, it is measured in the characteristic curve shown in FIG. 2 (b). This can be interpreted from the fact that the vertical fluctuation of the surface roughness is reduced along the length.

  In other words, in this embodiment, the undulation caused by plastic flow is suitably buffered by the nonwoven fabric by sandwiching the upper and lower surfaces of the CFRP substrate with a nonwoven fabric that is not impregnated with resin and is harder than the CFRP substrate. Therefore, the swell does not reach the surface side of the SMC molded product, and the generation of the depression is prevented.

  Further, even in the case where the rib forming concave portion is formed in the lower mold in order to give high rigidity to the SMC molded product, in this embodiment, the nonwoven fabric which is not impregnated with resin and is harder than the CFRP base material By sandwiching the upper and lower surfaces of the CFRP base material, it was possible to suppress the plastic flow molding material from flowing into the rib molding recess and generating depressions on the surface of the SMC molded product (see FIG. 3). .

  As shown in FIG. 3, the non-woven fabric provided on the upper surface of the CFRP base material functions like a so-called weight, so that only the portion of the molding material corresponding to the upper part of the rib molding recess is rib-molded. Inflow into the concave portion for use is suppressed, and plastic flow of the molding material in the substantially horizontal direction portion adjacent to the concave portion for rib forming is promoted. As a result, in this embodiment, no depression was formed on the upper surface of the CFRP base material, and a plurality of ribs could be suitably formed on the back surface side of the SMC molded product.

  Furthermore, in this example, the Vf (fiber volume content) of the carbon fiber in the CFRP base material is set to 20%, which can be suitably applied to an SMC molded product in which the Vf is suppressed to a low level. . In Patent Document 1 and Patent Document 2 described in the prior art, the volume content Vf of the inorganic substance in the material composition is set to a material of 45% or more, and the Vf is set to less than 45%. In this case, there is a possibility that the amount of resin shrinkage becomes large and the surface smoothness of the molded product cannot be obtained.

[Comparative example]
Next, a comparative example shown in FIG. 4 will be described. In this comparative example, in the SMC molding material, a non-woven fabric is not interposed between a plurality of CFRP base materials, and only the first to third CFRP base materials are directly and sequentially superimposed to form a prepreg laminate. This is different from the present embodiment in that it is configured.

  Fig.5 (a) is a partial expanded longitudinal cross-sectional view of the SMC molded product after a pressurizing force was given with the punch with respect to the SMC molding material shape | molded by the comparative example, FIG.5 (b) is a comparative example. It is a characteristic view which shows the surface roughness of the surface of the said SMC molded product shape | molded by (3). The surface roughness was measured based on JIS standard B-0601.

  In the comparative example, when a pressing force is applied to the prepreg laminate from above, the carbon fibers contained in the CFRP base material are shaped while being swelled by plastic flow under the action of the pressing force. Is understood from part A and part B in FIG. This is because the portion A and the portion B in FIG. 5A are greatly curved and undulated as compared with the other portions.

  Therefore, in the comparative example, the shrinkage of the resin in the thickness direction (vertical direction) of the SMC molded product could not be suppressed. As a result, in the comparative example, a resin-rich portion continuous in the thickness direction of the SMC molded product was generated, and a depression caused by resin shrinkage on the surface side of the SMC molded product (the uppermost surface of the laminate) was generated.

  Further, in the comparative example, in the characteristic curve shown in FIG. 5B, the fluctuation in the vertical direction of the surface roughness along the measurement length is increased as a whole, and in particular, A in FIG. It can be seen that the surface roughness greatly fluctuates corresponding to the undulations shown in the part and the part B, and a depression is formed.

  Further, in the comparative example, when the rib molding recess is formed in the lower mold in order to impart high rigidity to the SMC molded product, the plastically flowed molding material flows into the rib molding recess and the surface of the SMC molded product. A depression was generated in the surface (see FIG. 6).

It is a longitudinal cross-sectional view which shows the state which concerns on a present Example and the prepreg laminated body which is SMC molding material was mounted in the cavity of a press molding die. (A) is a partially enlarged longitudinal sectional view of an SMC molded product according to the present example after pressure is applied to the SMC molding material, and (b) is the SMC molded according to the present example. It is a characteristic view which shows the surface roughness of the surface of goods. In a present Example, the said SMC molding material is a longitudinal cross-sectional view which shows the state which flows into the recessed part for rib shaping | molding. It is a longitudinal cross-sectional view which shows the state which concerns on the comparative example and the prepreg laminated body which is SMC molding material was mounted in the cavity of a press-molding die. (A) is a partially enlarged longitudinal sectional view of an SMC molded product according to a comparative example after pressure is applied to the SMC molding material, and (b) is a view of the SMC molded product molded according to the comparative example. It is a characteristic view which shows the surface roughness of the surface. In a comparative example, it is a longitudinal cross-sectional view which shows the state in which the said SMC molding material flows into the recessed part for rib shaping | molding.

Claims (3)

In the method for producing a fiber-reinforced composite material,
A step of impregnating a reinforcing fiber material with a resin to form a sheet-like prepreg;
When laminating a plurality of the prepregs and molding with a molding die, a step of forming a prepreg laminate between the prepreg layers by interposing a non-impregnated base material;
A step of curing the resin after impregnating the resin with the prepreg laminate;
A method for producing a fiber-reinforced composite material, comprising: In the manufacturing method of the fiber reinforced composite material of Claim 1,
The method for producing a fiber-reinforced composite material, wherein the unimpregnated base material comprises at least one of a nonwoven fabric and a woven fabric.   A fiber-reinforced composite material produced by the method according to claim 1.