JP2008308626A - Sheet-like fiber-reinforced composite material and production method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet-like fiber-reinforced composite material having an excellent mechanical property, produced at lower cost than a conventional method or means. <P>SOLUTION: This sheet-like fiber-reinforced composite material consists of a fiber-reinforced material such as woven fabric and a thermoplastic resin. In the sheet-like fiber-reinforced composite material, the fiber-reinforced material is locally distributed at least in one surface layer portion. Preferably, a layer of a lower fiber volume content Vf than the surface layer portion or a fiber non-containing layer (a thermoplastic resin layer) not containing the fiber-reinforced material is present in a central portion of the sheet-like fiber-reinforced composite material, and a thickness of the central portion is at least a tenth of a thickness of the whole fiber-reinforced composite material. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a sheet-like fiber reinforced composite material comprising a fiber reinforcing material and a matrix resin, and a method for producing the same.

In recent years, fiber reinforcing materials such as carbon fibers, glass fibers, and aramid fibers have been combined with various matrix resins, and the resulting fiber reinforced composite materials have been widely used in various fields and applications. And in the aerospace field and general industrial fields where high mechanical properties and heat resistance are required, conventionally, thermosetting resins such as unsaturated polyester resin, epoxy resin, and polyimide resin have been used as matrix resins. It has been. However, especially in the aerospace field, these matrix resins have the drawbacks of being brittle and inferior in impact resistance, and therefore, improvement has been demanded. In the case of a thermosetting resin, when this is used as a prepreg, there are problems in storage management of the prepreg due to the life of the resin, etc., poor followability to the product shape, long molding time and low productivity, etc. There was also a problem.

On the other hand, in the case of a thermoplastic resin prepreg, the impact resistance when made into a composite material is excellent, the storage management of the prepreg is easy, the molding time is short, and the molding cost may be reduced. As a method for producing a thermoplastic resin prepreg, conventionally, for example, a method in which a film-like resin is heated and melted and impregnated into a fiber reinforcement as a base material (melt impregnation method, see Patent Document 1), a powdery resin is used. There are a method of applying and fusing to a fiber reinforcement by a fluidized bed method or a suspension method (powder method, see Patent Document 2), a method of dissolving a resin and removing the solvent after impregnating the fiber reinforcement (solution impregnation method). Are known. In addition, when a multiaxial fabric is used, as a method of improving the surface smoothness and uniformity, a low melting point polymer is used when forming a fiber reinforced plastic molded product by using a low melting point polymer for the stitch yarn of the multiaxial fabric. There has also been proposed a method in which a stitch yarn is melted by heat-forming at a melting point or higher (Patent Document 3).
JP 2002-19062 A Japanese Patent Publication No. 4-12894 JP 2002-227066 A

On the other hand, as a molding method of fiber reinforced composite material, conventionally, autoclave molding using a prepreg in which a fiber reinforcing material is impregnated with a resin has been mainly used.
In recent years, there has been a high demand for cost reduction of molded products, and in addition to the conventional autoclave molding method, a resin film infusion molding method (RFI method) using the melt impregnation method has been widely performed. However, in any case, the conventional method and means are expensive in the fiber reinforced composite material obtained, and development of an improved technique has been desired particularly in terms of cost reduction of the fiber reinforcing material.

An object of the present invention is to provide a sheet-like fiber-reinforced composite material having excellent mechanical properties, which is manufactured at a lower cost than conventional methods and means.

The invention described in claim 1 of the present invention is a sheet-like fiber reinforced composite material composed of a fiber reinforcing material and a thermoplastic resin, and the fiber reinforcing material is unevenly distributed in at least one surface layer portion. It is a sheet-like fiber-reinforced composite material. And as a fiber reinforcement of a surface layer part, a textile fabric is preferable (invention of Claim 2).

In a preferred embodiment of the invention described in claim 1, a non-fiber-containing layer (thermoplastic resin layer) that does not contain a fiber reinforcement is present in the central portion of the sheet-like fiber-reinforced composite material. The thickness of the containing layer is a sheet-like fiber-reinforced composite material that is at least one-tenth the thickness of the entire fiber-reinforced composite material (Invention of Claim 3).

In another preferred embodiment of the invention described in claim 1, a layer having a lower fiber volume content (Vf) than the surface layer portion is present in the central portion of the sheet-like fiber-reinforced composite material, It is a sheet-like fiber-reinforced composite material in which the thickness of the layer having a low fiber volume content is at least 1/10 of the total thickness of the fiber-reinforced composite material (Invention of Claim 4).

One of the manufacturing methods of the sheet-like fiber reinforced composite material of this invention described in Claim 1 is a fiber reinforcement material on both surfaces or one surface of the fiber-free layer (thermoplastic resin layer) which does not contain a fiber reinforcement material. And a layer of thermoplastic resin are disposed to form a laminate, and then the laminate is integrally fused by heating and pressurizing (Invention of Claim 5).

Another aspect of the method for producing a sheet-like fiber reinforced composite material of the present invention is that the fiber volume content is higher on both sides or one side of the layer composed of the fiber reinforcing material and the thermoplastic resin than the layer. A sheet-like fiber-reinforced composite material, characterized in that a layer comprising a material and a thermoplastic resin is arranged to form a laminate, and then the laminate is integrally fused by heating and pressing. This is a method (invention of claim 7).

In the inventions of the manufacturing methods of the fifth and seventh aspects, in any case, a woven fabric is preferable as the fiber reinforcement of the surface layer portion (the inventions of the sixth and eighth aspects).

The sheet-like fiber-reinforced composite material obtained by the present invention can be manufactured at a lower cost than that obtained by the conventional method and means, and its mechanical properties are not inferior to those obtained by the conventional method and means. Is. Moreover, the sheet-like fiber-reinforced composite material of the present invention contributes to weight reduction of the material although it has excellent mechanical properties.

The fiber-reinforced composite material of the present invention comprises a sheet-like fiber reinforcing material and a thermoplastic resin, and the fiber reinforcing material is unevenly distributed in at least one surface layer portion. In the present invention, the surface layer portion means a portion including the upper surface of the sheet (surface portion) or a portion including the lower surface (back surface portion), and the central portion includes a portion including the upper surface and a lower surface. It means a part sandwiched between parts. In the present invention, the fiber reinforcement is unevenly distributed in at least one surface layer portion, that is, the front surface portion and / or the back surface portion.

One of the preferred embodiments of the present invention is a sheet-like fiber-reinforced composite material in which the fiber reinforcement is unevenly distributed on the front surface portion and / or the back surface portion, and the fiber does not include a fiber reinforcement material in the center portion thereof. There is a non-containing layer (a layer made of only a thermoplastic resin), and the thickness of the non-fiber-containing layer is at least 1/10 of the total thickness of the fiber-reinforced composite material. Preferably, it is in the range of 1/10 to 3/4. When the thickness of the non-fiber-containing layer is less than 1/10, it does not meet the object of the invention of reducing the fiber reinforcement.

In another preferred embodiment of the present invention, the fiber reinforcing material is a sheet-like fiber-reinforced composite material that is unevenly distributed on the front surface portion and / or the back surface portion, and the fiber volume content rate in the central portion compared to the surface layer portion. In which the thickness of the low fiber volume content layer is at least one-tenth of the total thickness of the fiber-reinforced composite material. Preferably, it is in the range of 1/10 to 3/4. When the thickness of the non-fiber-containing layer is less than 1/10, it does not meet the object of the invention of reducing the fiber reinforcement.

The form of the fiber reinforcing material unevenly distributed on the front surface part and / or the back surface part may be any sheet-like material as described below, but is preferably a woven fabric. A woven fabric may be used for the front surface portion and / or the back surface portion, and a sheet-like material other than the woven fabric may be used for the central portion.

Examples of the fiber reinforcing material used in the present invention include inorganic fibers, organic fibers, metal fibers, or fibers made of a mixture thereof. Examples of the inorganic fiber include carbon fiber, graphite fiber, silicon carbide fiber, alumina fiber, tungsten carbide fiber, boron fiber, and glass fiber. Examples of organic fibers include aramid fibers, high-density polyethylene fibers, and other general organic fibers such as nylon and polyester. As the metal fibers, fibers such as stainless steel and iron can be used, and there are also carbon fibers coated with metal. Particularly preferred is carbon fiber. In the case of carbon fibers, strands of 200-1600 tex and 3K-24K filaments are preferred.

In the present invention, the fiber reinforcement is used in the form of a sheet. In the present invention, the sheet form means a flat form such as a woven or knitted fabric of fiber reinforcement, a multiaxial woven fabric, or a unidirectionally arranged sheet of strands. Carbon fiber paper made using chopped strands may be used. In addition, multiaxial woven fabrics are generally nylon yarns, polyester yarns, glass fibers, which are bundles of fiber reinforcements aligned in one direction and laminated in a sheet form (multiaxial woven fabric base material). This refers to a woven fabric that is stitched by stitches such as yarns, penetrates the laminate in the thickness direction, and reciprocates between the front and back surfaces of the laminate along the surface direction. Preferred in the present invention is a fabric obtained by carbon fiber or a mixture of carbon fiber and other fibers, for example, a plain fabric, a twill fabric, or a multiaxial fabric.

In the fiber-reinforced composite material of the present invention, the fiber volume content (Vf) is 10 to 60%, preferably 20 to 50%. Therefore, the volume content of the thermoplastic resin is 90 to 40%, preferably 80 to 50%. %, And the ratio of the fiber reinforcement is lower than that of a normal prepreg. Therefore, when the fiber reinforcement is expensive, it is advantageous in terms of cost. In addition, since the specific gravity of the fiber reinforcing material is higher than that of the matrix resin, the weight of the product is expected to be reduced by reducing the ratio of the fiber reinforcing material.

Examples of the thermoplastic resin used in the present invention include polypropylene, polysulfone, polyethersulfone, polyetherketone, polyetheretherketone, aromatic polyamide, aromatic polyester, aromatic polycarbonate, polyphenylene sulfide, polyetherimide, and poly Examples thereof include one or more resins selected from the group consisting of arylene oxide, thermoplastic polyimide, polyamideimide, polybutylene terephthalate, polyethylene terephthalate, polyethylene naphthalate, polyethylene, acrylonitrile butadiene styrene, and polylactic acid. Moreover, depending on a use, it can also be mixed and used partially with a thermosetting resin. Of these, polyamide resins and acrylonitrile butadiene styrene (ABS) resins excellent in heat resistance, elastic modulus, and chemical resistance are particularly preferable. These thermoplastic resins may contain commonly used colorants and various additives.

The sheet-like fiber-reinforced composite material of the present invention can be preferably produced by the method described below.

One method is to form a laminate by disposing a layer comprising a fiber reinforcement and a thermoplastic resin on both sides or one side of a fiber-free layer (thermoplastic resin layer) that does not contain a fiber reinforcement, and then forming the laminate. In this method, the laminate is integrally fused by heating and pressing. As the fiber reinforcing material disposed on both surfaces or one surface of the non-fiber-containing layer (thermoplastic resin layer), a woven fabric is preferable.

Another method is a laminate in which a layer composed of a fiber reinforcement and a thermoplastic resin having a fiber volume content higher than that of the layer composed of a fiber reinforcement and a thermoplastic resin is disposed on both sides or one side of the layer. Is formed, and then the laminate is integrally fused by heating and pressing. As the fiber reinforcement disposed on both sides or one side of the layer composed of the fiber reinforcement and the thermoplastic resin forming the central portion, a woven fabric is preferable. As the fiber reinforcing material forming the central portion, a sheet-like material having a form other than the woven fabric may be used.

As a method of fusing the laminated body integrally by heating and pressurizing treatment, for example, the laminated body is sandwiched between steel belts and heated and pressurized by passing the steel belt between hot rolls, or intermittent press. By doing so, there is a method of melting and integrating the thermoplastic resin. Alternatively, there are a method in which the laminated body is continuously heated and cooled by a belt press, a method in which the laminated body is preheated by a far infrared heater and then cold-pressed, or a batch method in which a heated and cooled press is used. The heating temperature is preferably 150 to 400 ° C. and the pressure is preferably about 0.1 to 10 MPa.

One or a plurality of sheet-like fiber reinforced composite materials obtained in the present invention are laminated and molded by a die pressing method, an autoclave method, a heating / cold pressing method, or the like to obtain a fiber reinforced plastic molded product. At this time, in order to adjust the fiber volume fraction (Vf) or the resin content in the molded product, a thermoplastic resin film can be additionally laminated as necessary. The content of the thermoplastic resin in the molded product is usually 10 to 90% by weight, preferably 30 to 70% by weight.

Hereinafter, the present invention will be described in detail by way of examples.

[Example 1]
As the fiber reinforcement, carbon fiber HTA-12K (12,000 long strand fibers, 800 tex, manufactured by Toho Tenax Co., Ltd.) was used. The basis weight of this long fiber oriented in one direction is 200 g / m ^2.
4 pieces of PA6 film (Unitika, weight per unit: 28.75 g / m ² ) is inserted in the middle of the multi-axial woven fabric base material (two laminated at an angle of [0/90]), and polyester stitch yarn To obtain a multiaxial fabric having a PA6 film between the layers.

The molded plate was molded, and first, the surface reinforcing layer of the molded plate was laminated and constituted. That is, two PA6 films were prepared on each of the upper and lower surfaces of the multiaxial woven fabric, and the two layers were stacked to form a surface reinforcing layer having a Vf of about 40%. Next, 30 PA6 films are inserted into the central portion of the laminate in the thickness direction so that a layer containing no fiber reinforcement (Vf = 0%) is formed between the two surface reinforcing layers thus obtained. did. Vf was about 23% for the entire molded plate. The laminated structure of the obtained laminate has a surface layer of 0 ° or 90 ° [[0/90] / [45 / −45]] / resin layer / [[[so that the surface reinforcing layer becomes pseudo-isotropic. −45/45] / [90/0]].

Subsequently, it shape | molded to the shaping | molding board. That is, the laminate obtained above was placed on a mold, placed on a press machine heated to 295 ° C., the mold temperature was raised to 285 ° C. and kept for 10 minutes, and then the molding surface pressure was increased. The pressure was increased to 10 kg / cm ² . After pressurization, the mold was cooled to a mold temperature of 50 ° C. or lower and demolded. A cross-sectional observation image of the obtained molded plate is shown in FIG. The obtained molded plate was subjected to a three-point bending property test. At that time, the test piece was prepared so that the fiber orientation of the outermost layer was 0 ° with respect to the longitudinal direction of the test piece. Further, from the observation inside the obtained molded plate, the Vf = 0% layer was about one third of the entire molded plate. The physical properties of the obtained molded plate were as shown in Table 1.

[Comparative Example 1]
Four multiaxial fabrics having a PA6 film between the layers used in Example 1 were used, and the PA6 film was sandwiched between these layers, so that the molded plates were laminated so that Vf = 23%. The laminated structure is [[[0/90] / [45 / −45]] ₂ ] s in which the surface layer is 0 ° or 90 ° as pseudo-isotropic. The molded plate and the test piece were produced in the same manner as in Example 1. The physical properties of the obtained molded plate were as shown in Table 1.

[Example 2]
A carbon fiber paper material produced using a chopped strand of carbon fiber is inserted into the central part in the thickness direction of Vf = 0% of the laminate produced in Example 1, and the central part is Vf = 10%, the laminate. The whole was laminated so that Vf = 28%, and a molded plate having a low Vf central portion was produced. The forming method of the forming plate and the measuring method of the test piece were performed in the same manner as in Example 1. Moreover, from the observation inside the obtained molded plate, the low Vf layer was about one third of the entire molded plate. The physical properties of the obtained molded plate were as shown in Table 1.

[Comparative Example 2]
Four multiaxial fabrics having a PA6 film between the layers used in Example 1 were used, and the PA6 film was sandwiched between these layers, so that the molded plates were laminated so that Vf = 28%. The laminated structure is [[[0/90] / [45 / −45]] ₂ ] s in which the surface layer is 0 ° or 90 ° as pseudo-isotropic. The molded plate and the test piece were produced in the same manner as in Example 1. The physical properties of the obtained molded plate were as shown in Table 1.

[Comparative Example 3]
Eight multiaxial woven fabrics having a PA6 film between the layers used in Example 1 and a PA6 film between the layers were laminated so that Vf = 45% with a molding plate. The laminated structure is [[[0/90] / [45 / −45]] ₂ ] s in which the surface layer is 0 ° or 90 ° as pseudo-isotropic. The molded plate and the test piece were produced in the same manner as in Example 1. A cross-sectional observation image of the obtained molded plate is shown in FIG. The physical properties of the obtained molded plate were as shown in Table 1.

As can be seen from Table 1, the composite material of Example 1 or 2 of the present invention in which the fiber reinforcing material is unevenly distributed in the surface layer portion has bending elasticity compared to that of Comparative Example 1 or 2 having the same fiber volume content. The rate and bending strength are better. Further, as can be seen from Comparative Example 3, the flexural modulus and flexural strength of the composite material of Example 1 with a fiber volume content of 23% or the composite material of Example 2 with a fiber volume content of 28% are the fiber volume. It is comparable to that of Comparative Example 3 with a content of 50%.

It is a figure which shows the cross-sectional observation image of the shaping | molding board obtained by this invention (Example 1). It is a figure which shows the cross-sectional observation image of the shaping | molding board obtained by the comparative example (comparative example 3).

Claims (8)

A sheet-like fiber-reinforced composite material comprising a fiber-reinforced material and a thermoplastic resin, wherein the fiber-reinforced material is unevenly distributed in at least one surface layer portion. 2. The sheet-like fiber reinforced composite material according to claim 1, wherein the fiber reinforced material of the surface layer portion is a woven fabric. There is a fiber-free layer (thermoplastic resin layer) that does not contain a fiber reinforcement at the center of the sheet-like fiber-reinforced composite material, and the thickness of the fiber-free layer is the thickness of the entire fiber-reinforced composite material. 3. The sheet-like fiber-reinforced composite material according to claim 1, wherein the fiber-reinforced composite material is at least 1/10 of the above. In the central part of the sheet-like fiber reinforced composite material, there is a layer having a lower fiber volume content than the surface layer part, and the thickness of the layer having the lower fiber volume content is the thickness of the entire fiber reinforced composite material. The sheet-like fiber-reinforced composite material according to claim 1 or 2, which is at least 1/10. A layer composed of a fiber reinforcing material and a thermoplastic resin is disposed on both sides or one side of a non-fiber-containing layer (thermoplastic resin layer) not containing a fiber reinforcing material to form a laminate, and then the laminate is heated and A method for producing a sheet-like fiber-reinforced composite material, wherein the sheet-like fiber-reinforced composite material is integrally fused by pressure treatment. The method for producing a sheet-like fiber-reinforced composite material according to claim 5, wherein the fiber reinforcing material disposed on both sides or one side of the non-fiber-containing layer (thermoplastic resin layer) not containing the fiber reinforcing material is a woven fabric. On both sides or one side of the layer consisting of a fiber reinforcement and a thermoplastic resin, a fiber volume content is higher than the layer, a layer consisting of a fiber reinforcement and a thermoplastic resin is placed to form a laminate, and then A method for producing a sheet-like fiber-reinforced composite material, wherein the laminate is integrally fused by heat and pressure treatment. The method for producing a sheet-like fiber-reinforced composite material according to claim 7, wherein the fiber reinforcing material disposed on both sides or one side of the layer composed of the fiber reinforcing material and the thermoplastic resin is a woven fabric.

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