JP7363630B2 - Prepreg laminate, fiber reinforced composite material and method for producing fiber reinforced composite material - Google Patents

Description

The present invention relates to a fiber-reinforced composite material with an excellent design, a method for manufacturing the fiber-reinforced composite material, and a prepreg laminate suitably used therein.

Fiber-reinforced composite materials are useful because they have excellent strength, rigidity, and electrical conductivity, and are used in aircraft structural components, windmill blades, automobile exterior materials, automobile interior materials, and IC trays and notebook computer casings ( They are widely used in computer applications such as housings), and their demand is increasing year by year.

Fiber-reinforced composite materials are materials made by molding prepreg, which has reinforcing fibers and resin as essential components, and in this case, air and volatile components remain in the resin part of the prepreg before and during molding. It is known that the resulting fiber-reinforced composite material has pinholes on the surface and voids inside. Therefore, various techniques have been proposed for the purpose of reducing pinholes and internal voids on the surface of fiber-reinforced composite materials obtained from prepreg. Various techniques have also been proposed for the purpose of improving the shapeability and molding robustness of prepreg.

One of these proposals is to mold a fiber-reinforced composite material from a prepreg laminate made by laminating a prepreg in which reinforcing fibers are impregnated with a resin and a base material not impregnated with a resin (see Patent Document 1). ). This technology is proposed to provide fiber-reinforced composite materials with an excellent design. Separately, there is also a prepreg having a layer containing reinforcing fibers impregnated with a resin composition, wherein the content of the resin composition in the prepreg is within a predetermined range, and at least a part of the fibers has a predetermined length by a plurality of cuts. A technology has been proposed to provide a prepreg that is composed of reinforcing fibers, has excellent formability into three-dimensional shapes, and has excellent molding robustness that suppresses molding defects that cause a decrease in component strength. (See Patent Document 2). Furthermore, by laminating triaxial fabric and nonwoven fabric, it has strength, elastic modulus, and high specific strength similar to fiber-reinforced composite materials, and has electrical conductivity, insulation, thermal conductivity, and heat insulation properties comparable to metal materials. A technique for providing a composite material, a molded product, and a prepreg having at least one of the above has been proposed (see Patent Document 3).

However, with these technologies, it is necessary to provide fiber-reinforced composite materials with an excellent design, improve the shapeability and molding robustness of prepreg, and improve the electrical conductivity, insulation, thermal conductivity, and heat insulation of fiber-reinforced composite materials. Although it is possible to improve at least one of the properties, it has been difficult to achieve both the shapeability of the prepreg and the excellent design of the fiber reinforced composite material.

International publication 2018/079475 pamphlet International publication 2016/043156 pamphlet International publication 2002/018127 pamphlet

An object of the present invention is to provide a carbon fiber-reinforced composite material with an excellent design, a method for producing the fiber-reinforced composite material, and a prepreg laminate with excellent shapeability that is suitably used therein.

In order to achieve the above object, the present invention has any of the following configurations.

The present invention provides a prepreg in which reinforcing fibers are impregnated with a resin on one surface of a fiber base material [b] that is not impregnated with a resin, and in which at least some of the reinforcing fibers have a fiber length by a plurality of cuts. Laminating one or more layers of cut prepreg [a] composed of reinforcing fibers having a length (L) of 10 to 300 mm and having a volume content Vf of the reinforcing fibers in the range of 45 to 65%, and It is a prepreg laminate having a sandwich structure in which one or more layers of prepreg [c] in which reinforcing continuous fibers are impregnated with resin are laminated on the other surface of the fiber base material [b].

According to a preferred embodiment of the prepreg laminate of the present invention, at least one surface of the prepreg laminate is a designed surface, and the fiber base material [b] is laminated as the second or third layer from the designed surface side. This is a prepreg laminate.

According to a preferred embodiment of the prepreg laminate of the present invention, it is a prepreg laminate in which the cut prepreg [a] has a thickness of 30 to 300 μm.

According to a preferred embodiment of the prepreg laminate of the present invention, the reinforcing fibers constituting the cut prepreg [a] are carbon fibers, and the resin is a thermosetting resin.

According to a preferred embodiment of the prepreg laminate of the present invention, the fiber base material [b] contains carbon fibers or glass fibers, the carbon fibers or glass fibers are discontinuous, and the basis weight is 5 to 100 g/m. ² , which is a prepreg laminate.

Further, the fiber reinforced composite material of the present invention uses the prepreg laminate to form a fiber reinforced composite material layer [A] originating from the cut prepreg [a] and the cut prepreg [a] or the prepreg [a]. The fiber-reinforced composite material includes at least a fiber-reinforced composite material layer [B] derived from the fiber base material [b] containing the resin impregnated in the fiber-reinforced composite material layer [B].

According to a preferred embodiment of the carbon fiber reinforced composite material of the present invention, the fiber volume content VfA (%) of the fiber reinforced composite material layer [A] and the fiber volume content VfB of the fiber reinforced composite material layer [B] (%) is a fiber reinforced composite material having a relationship of VfA>VfB.

Moreover, the method for producing a fiber-reinforced composite material of the present invention is a method for producing a fiber-reinforced composite material, which includes a molding step of applying pressure to the outside of the prepreg laminate while heating the prepreg laminate.

According to a preferred embodiment of the method for producing a carbon fiber reinforced composite material of the present invention, the forming step further includes a step of applying a pressure of -80 kPa or less (gauge pressure) inside the prepreg laminate. This is the manufacturing method.

According to a preferred embodiment of the method for producing a carbon fiber reinforced composite material of the present invention, in the molding step, the fiber base material [b] is impregnated with the resin contained in the cut prepreg [a] or the prepreg [c]. , a method for producing fiber-reinforced composite materials.

According to the present invention, by laminating the cut prepreg into the prepreg laminate, it is possible to achieve both excellent formability of the prepreg and an excellent design in the fiber-reinforced composite material obtained by molding. .

FIG. 1 is a schematic diagram of a prepreg laminate according to one embodiment of the present invention. FIG. 3 is a schematic diagram of a prepreg laminate according to another embodiment of the present invention. FIG. 3 is a schematic diagram of a prepreg laminate according to another embodiment of the present invention. FIG. 2 is a conceptual diagram showing an example of a cut pattern of the notched prepreg of the present invention.

Embodiments will be described below with reference to the drawings. Note that the present invention is not limited to the figures or examples.

As shown in FIG. 1, the prepreg laminate according to the present invention includes at least a cut prepreg [a] 2 whose reinforcing fibers are impregnated with a resin, and a fiber base material [b] 3 which is not impregnated with a resin. It is important that the prepreg laminate 10 is used. In addition, as shown in FIG. 2, a prepreg laminate with a sandwich structure in which cut prepreg [a] 2 made of reinforcing fibers impregnated with resin is laminated on both sides of a fiber base material [b] 3 that is not impregnated with resin. The body is also preferably used. Furthermore, as shown in FIG. 3, a cut prepreg [a] 2 made of reinforcing fibers impregnated with resin is laminated on one surface of the fiber base material [b] 3 that is not impregnated with resin. A prepreg laminate 10 having a sandwich structure in which prepreg [c] 4 impregnated with continuous reinforcing fibers is laminated is also preferably used.

When the prepreg laminate 10 is compression-molded by a press or the like, the resin impregnated in the prepreg [a] 2 or the prepreg [c] 4 moves to the fiber base material [b] 3 and impregnates between the fibers. By laminating the prepreg [a] 2 or prepreg [c] 4, the fiber base material [b] 3 is impregnated with sufficient resin, thereby forming the prepreg [a] 2 or prepreg [c] 4 that becomes the design surface. By transferring air and volatile components together with the resin contained in the fiber base material [b] 3, a fiber reinforced composite material having an excellent design surface 1 can be obtained.

The cut prepreg [a] 2 used in the present invention is made by impregnating at least reinforcing fibers with a resin.

There are no particular restrictions on the reinforcing fibers used in the cut prepreg [a] 2, and examples include metal fibers such as aluminum fibers, brass fibers, and stainless steel fibers, PAN-based carbon fibers, rayon-based carbon fibers, and lignin-based carbon fibers. , pitch-based carbon fibers, graphite fibers, insulating fibers such as glass fibers, organic fibers such as aramid fibers, PBO fibers, polyphenylene sulfide fibers, polyester fibers, acrylic fibers, nylon fibers, polyethylene fibers, Examples include inorganic fibers such as silicon carbide fiber and silicon nitride fiber. Moreover, these fibers may be surface-treated. Surface treatments include treatment with a coupling agent, treatment with a sizing agent, treatment with a binding agent, treatment with an additive, and the like, in addition to treatment with a metal as a conductor. Moreover, these reinforcing fibers may be used alone or in combination of two or more types.

Among these, carbon fibers such as PAN-based carbon fibers, pitch-based carbon fibers, and rayon-based carbon fibers, which are excellent in specific strength and specific rigidity, are preferably used from the viewpoint of weight reduction effects. Further, from the viewpoint of increasing the economic efficiency of the resulting laminate, glass fiber is preferably used, and in particular, from the viewpoint of a balance between mechanical properties and economic efficiency, it is preferable to use carbon fiber and glass fiber in combination. Furthermore, from the viewpoint of improving the shock absorbing properties and formability of the resulting laminate, aramid fibers are preferably used, and in particular, it is preferable to use carbon fibers and aramid fibers in combination from the viewpoint of the balance between mechanical properties and shock absorbing properties. Furthermore, from the viewpoint of increasing the conductivity of the resulting laminate, reinforcing fibers coated with metal such as nickel, copper, or ytterbium can also be used. Among these, PAN-based carbon fibers, which are excellent in mechanical properties such as strength and elastic modulus, can be more preferably used.

The reinforcing fibers used in the cut prepreg [a] 2 are in the form of a unidirectional base material in which reinforcing fibers are aligned in one direction, bidirectional fabrics, multiaxial fabrics, nonwoven materials, mats, knitted fabrics, braided cords, etc. However, it is preferable to use any of them in the form of a fabric-like base material with continuous reinforcing fibers. The form of the reinforcing fibers can be freely selected depending on the purpose and area of use. Among these, a unidirectional base material in which fibers are arranged in one direction is preferable because the fibers can be packed well and Vf can be efficiently improved, so that the mechanical properties can be exhibited to the highest degree. The cut prepreg [a] 2 is made by cutting a base material made of this continuous fiber so as to have the fiber length (L). Regarding the fiber length (L), it is important that at least some of the fibers are composed of reinforcing fibers with a length of 10 to 300 mm. By setting the fiber length (L) of the reinforcing fibers within this range, it is possible to ensure the number of gas degassing passes in the out-of-plane direction during molding and to effectively suppress bridging. . When L is set to 10 mm or more, the distance between the notches increases, so when a load is applied to fiber-reinforced plastic molded using such a notch prepreg, cracks will not connect easily and the product will have high strength. becomes. Considering the relationship between the shape followability during molding, the effect of suppressing molding defects such as voids, and the mechanical properties of the molded fiber-reinforced plastic, a more preferable range of the fiber length L of the reinforcing fibers separated by the cuts is It is 10 to 100 mm.

Furthermore, it is important that the volume content Vf of reinforcing fibers in the cut prepreg [a] 2 is within the range of 45 to 65%. By setting the volume content Vf of the reinforcing fibers to 65% or less, the reinforcing fibers are displaced at the cut portion, effectively suppressing bridging, and obtaining shape followability and the effect of suppressing molding defects such as voids. I can do it. From this point of view, it is more preferable that Vf is 60% or less. Furthermore, the lower Vf is, the more bridging can be suppressed, but when Vf is less than 45%, it becomes difficult to obtain the high mechanical properties required for the structural material. From this point of view, it is more preferable that Vf is 55% or more. The volume content Vf of the reinforcing fibers can be measured by curing the prepreg by the method described in Examples and then processing the image with an optical microscope or a laser microscope.

Furthermore, the resin used for the cut prepreg [a] 2 is not particularly limited, and both thermosetting resins and thermoplastic resins can be suitably used.

As the thermosetting resin, thermosetting resins such as epoxy resin, phenol resin, vinyl ester resin, benzoxazine resin, polyimide resin, oxetane resin, maleimide resin, unsaturated polyester resin, urea resin, melamine resin, etc. are preferably used. be able to. For these resins, resins made by blending two or more types may be used. Among these, epoxy resins, phenol resins, and vinyl ester resins are preferred from the viewpoint of mechanical properties and heat resistance of the laminate. In particular, epoxy resins are more preferred from the viewpoints of mechanical properties of the laminate, heat resistance, and handleability. In order to exhibit its excellent mechanical properties, the epoxy resin is preferably contained as a main component of the resin used, and specifically, it is preferably contained in an amount of 60% by weight or more based on the resin composition.

As the epoxy resin, epoxy resins whose precursors are amines, phenols, or compounds having a carbon-carbon double bond are preferably used.

As the curing agent for the epoxy resin, any compound having an active group capable of reacting with an epoxy group can be used. As the curing agent, compounds having an amino group, an acid anhydride group and an azide group are suitable. More specifically, the curing agent includes, for example, dicyandiamide, various isomers of diaminodiphenylmethane and diaminodiphenylsulfone, aminobenzoic acid esters, various acid anhydrides, phenol novolak resin, cresol novolak resin, polyphenol compounds, imidazole derivatives. , aliphatic amines, tetramethylguanidine, thiourea-adducted amines, carboxylic acid anhydrides such as methylhexahydrophthalic anhydride, carboxylic acid hydrazides, carboxylic acid amides, polymercaptans, and Lewis compounds such as boron trifluoride ethylamine complexes. Examples include acid complexes. These curing agents may be used alone or in combination.

It is also suitable to use a thermoplastic resin dissolved in the thermosetting resin. Such thermoplastic resins generally include carbon-carbon bonds, amide bonds, imide bonds, ester bonds, ether bonds, carbonate bonds, urethane bonds, thioether bonds, sulfone bonds, and carbonyl bonds in the main chain. Although it is preferable that the thermoplastic resin has a bond, it may have a partially crosslinked structure. Further, it may be crystalline or amorphous. In particular, polyamide resin, polycarbonate resin, polyacetal resin, polyphenylene oxide resin, polyphenylene sulfide resin, polyarylate resin, polyester resin, polyamideimide resin, polyimide resin, polyetherimide resin, polyimide resin having a phenyltrimethylindane structure, polysulfone resin, At least one resin selected from the group consisting of polyether sulfone resin, polyether ketone resin, polyether ether ketone resin, polyaramid resin, polyether nitrile resin and polybenzimidazole resin is dissolved in a thermosetting resin. It is preferable to be present.

Examples of thermoplastic resins include polyolefin resins such as polyethylene resin, polypropylene resin, and polybutylene resin, and polyester resins such as polyethylene terephthalate resin, polybutylene terephthalate resin, polytrimethylene terephthalate resin, polyethylene naphthalate resin, and liquid crystal polyester. and polyarylene sulfide resins such as polyamide resins, polyoxymethylene resins, and polyphenylene sulfide resins, polyketone resins, polyetherketone resins, polyetheretherketone resins, polyetherketoneketone resins, polyethernitrile resins, and polytetrafluoroethylene resins. In addition to fluorine resins such as, crystalline resins such as liquid crystal polymer resins, polystyrene resins, polycarbonate resins, polymethyl methacrylate resins, polyvinyl chloride resins, polyphenylene ether resins, polyimide resins, polyamideimide resins, polyetherimide resins, polysulfone Resin, amorphous resin such as polyether sulfone resin, polyarylate resin, etc., phenolic resin, phenoxy resin, polystyrene resin, polyolefin resin, polyurethane resin, polyester resin, polyamide resin, polybutadiene resin. Examples include thermoplastic resins selected from thermoplastic elastomers such as polyisoprene resins, polyisoprene resins, fluororesins, and polyacrylonitrile resins, as well as copolymers and modified products thereof. Among these, polyolefin resins are preferred from the viewpoint of lightweight of the resulting laminate, polyamide resins are preferred from the viewpoint of strength, and polyester resins are preferably used from the viewpoint of surface appearance.

The thermoplastic resins exemplified in the above group may contain impact resistance improvers such as elastomers or rubber components, other fillers, and additives within a range that does not impair the object of the present invention. Examples of these include inorganic fillers, flame retardants, conductivity imparting agents, crystal nucleating agents, ultraviolet absorbers, antioxidants, vibration damping agents, antibacterial agents, insect repellents, deodorants, color inhibitors, and heat stabilizers. , a mold release agent, an antistatic agent, a plasticizer, a lubricant, a colorant, a pigment, a dye, a foaming agent, an antifoaming agent, or a coupling agent.

Further, a filler can be added to resin such as a thermosetting resin or a thermoplastic resin. Fillers include continuous reinforcing fibers, calcium carbonate, talc, silica, clay, glass flakes, catechin, zeolite, silica balloons, glass balloons, shirasu balloons, carbon black, carbon nanotubes, fullerene, graphite, metal powder, metal foil, Examples include ferrite materials, alumina, barium titanate, lead zirconate titanate, barium sulfate, titanium oxide, glass beads, alumina, antimony oxide, hydrotalcite, red phosphorus, zinc carbonate, calcium oxide, and the like. Among these, an intermediate base material containing continuous reinforcing fibers is preferred from the viewpoint of moldability.

The thickness of the cut prepreg [a] is preferably within the range of 30 to 300 μm. Thereby, it is possible to improve both the moldability of the prepreg laminate 10 and the design of the fiber-reinforced composite material. If the thickness is less than 30 μm, many pinholes may appear on the design surface of the resulting fiber-reinforced composite material, and if the thickness exceeds 300 μm, problems may occur when cutting into the prepreg. be.

The fiber base material [b] 3 used in the present invention is a base material composed of fibers in order to be easily impregnated with resin.

The fibers used for the fiber base material [b] 3 are not particularly limited, and include, for example, metal fibers such as aluminum fibers, brass fibers, and stainless steel fibers, PAN-based carbon fibers, rayon-based carbon fibers, and lignin-based carbon fibers. , pitch-based carbon fibers, graphite fibers, insulating fibers such as glass fibers, organic fibers such as aramid fibers, PBO fibers, polyphenylene sulfide fibers, polyester fibers, acrylic fibers, nylon fibers, polyethylene fibers, Examples include inorganic fibers such as silicon carbide fiber and silicon nitride fiber. Moreover, these fibers may be surface-treated. Surface treatments include treatment with a coupling agent, treatment with a sizing agent, treatment with a binding agent, treatment with an additive, and the like, in addition to treatment with a metal as a conductor. Moreover, these reinforcing fibers may be used alone or in combination of two or more types.

Among these, carbon fibers such as PAN-based carbon fibers, pitch-based carbon fibers, and rayon-based carbon fibers, which are excellent in specific strength and specific rigidity, are preferably used from the viewpoint of weight reduction effects. Furthermore, from the viewpoint of increasing the economic efficiency of the obtained prepreg laminate, glass fiber is preferably used, and in particular, from the viewpoint of a balance between mechanical properties and economic efficiency, it is preferable to use carbon fiber and glass fiber in combination. Furthermore, from the viewpoint of improving the shock absorbing properties and formability of the resulting laminate, aramid fibers are preferably used, and in particular, it is preferable to use carbon fibers and aramid fibers in combination from the viewpoint of the balance between mechanical properties and shock absorbing properties. Furthermore, from the viewpoint of increasing the conductivity of the resulting laminate, reinforcing fibers coated with metal such as nickel, copper, or ytterbium can also be used. Among these, PAN-based carbon fibers have excellent mechanical properties such as strength and elastic modulus, and glass fibers are more preferably used from the viewpoint of improving the economic efficiency of the resulting laminate.

The basis weight of the fiber base material [b] is preferably within the range of 5 to 100 g/m ² . Thereby, it is possible to improve both the moldability of the prepreg laminate 10 and the design of the fiber-reinforced composite material. Preferably, it is 5 to 80 g/m ² , more preferably 5 to 50 g/m ² .

If the basis weight is less than 5 g/m ² , there may be many pinholes on the design surface 1 of the resulting fiber-reinforced composite material, and if it exceeds 100 g/m ² , the impregnability of the resulting fiber-reinforced composite material may be affected. Problems may occur.

The fiber base material [b] 3 may be any material that is not impregnated with resin, and its form includes, for example, nonwoven fabric, woven fabric, knitted fabric, and mat, and is a discontinuous fiber in terms of resin impregnability. It is preferable.

Further, the thickness of the fiber base material [b] 3 is preferably within the range of 0.1 to 1.5 mm. Thereby, it is possible to achieve both impregnability into the fiber base material [b] 3 and designability of the fiber reinforced composite material. Preferably it is 0.1 to 1 mm, more preferably 0.1 to 0.5 mm. If the thickness is less than 0.1 mm, there may be many pinholes on the design surface of the fiber-reinforced composite material obtained, and if it exceeds 1.5 mm, there may be a problem with the impregnability of the fiber-reinforced composite material obtained. There is.

The prepreg [c] in which continuous reinforcing fibers are impregnated with resin used in the present invention preferably contains at least reinforcing fibers and resin.

The reinforcing fibers used in the prepreg [c] are not particularly limited, and the same reinforcing fibers as those described in the cut prepreg [a] can be used.

The form of the reinforcing fibers is preferably continuous, and the reinforcing fibers are preferably in the form of continuous fibers such as long fibers aligned in one direction, woven fabrics, tows, and rovings.

Further, the resin used for the prepreg [c] is not particularly limited, and the same resin as described for the cut prepreg [a] can be used.

The prepreg laminate 10 has a structure in which at least one surface of the prepreg laminate 10 is the design surface 1, and the fiber base material [b] 3 is laminated as the second or third layer from the outermost layer on the design surface 1 side. It is preferable that

As shown in FIG. 1, the structure in which the fiber base material [b] 3 is laminated as the second layer from the outermost layer on the design surface 1 side is as shown in FIG. By forming the prepreg laminate 10 in which [b] 3 is arranged, the air and volatile components of the cut prepreg [a] 2, which forms the design surface 1, are impregnated into the fiber base material [b] 3 together with the resin. This is preferable in that an excellent design aspect of the composite material can be obtained.

In addition, as a preferable lamination mode of the prepreg laminate 10, as shown in FIG. 2, the cut prepreg [a] 2b is arranged from the design surface 1, followed by the fiber base material [b] 3 and the cut prepreg [a] 2a. It can be a prepreg laminate 10. By having such a laminated structure, the lamination process is not complicated, and the air and volatile components of the cut prepreg [a] 2, which forms the design surface 1, are impregnated into the fiber base material [b] 3 together with the resin. , is preferable in that an excellent design surface 1 of the fiber-reinforced composite material can be obtained. It is also a preferred embodiment to laminate a plurality of cut prepreg [a] 2a and cut prepreg [a] 2b.

Furthermore, as another preferable lamination mode of the prepreg laminate 10, as shown in FIG. The arranged prepreg laminate 10 can also be preferably used. It is also preferable to use a plurality of cut prepregs [a] 2 and prepregs [c] 4 stacked together.

The fiber-reinforced composite material of the present invention includes a fiber-reinforced composite material layer [A] derived from a cut prepreg [a] in which reinforcing fibers are impregnated with at least a resin, and a fiber-reinforced composite material layer [A] derived from the cut prepreg [a] or the prepreg [c]. It is preferable that the fiber-reinforced composite material includes at least a fiber-reinforced composite material layer [B] derived from a fiber base material [b] containing a resin impregnated with a fiber-reinforced composite material layer [B]. When laminating prepreg [c] in which reinforcing fibers of continuous fibers are impregnated with resin, it is possible to include a fiber reinforced composite material layer [C] consisting of prepreg [c] in which reinforcing fibers of continuous fibers are impregnated with resin. can.

When laminating multiple layers of the cut prepreg [a] 2, fiber base material [b] 3, or prepreg [c] 4 constituting the prepreg laminate 10, the fiber type, resin type, fiber volume content, prepreg basis weight, It is also possible to use a combination of cut prepregs [a] 2, fiber base materials [b] 3, or prepregs [c] 4 having different fabric weights of reinforcing fibers, prepreg thicknesses, etc. In that case, the prepreg laminate 10 can be designed in accordance with the mechanical properties of the fiber-reinforced composite material, the thickness of the fiber-reinforced composite material, and the like.

Among the fiber-reinforced composite materials according to the present invention, the fiber-reinforced composite material layer [A] derived from the cut prepreg [a]2 is a fiber-reinforced composite material obtained by curing or solidifying the resin of the cut prepreg [a]2. It is. In addition, the fiber reinforced composite material layer [B] derived from the fiber base material [b] 3 is a fiber base material [b] containing the resin impregnated in the cut prepreg [a] 2 or the prepreg [c] 4. 3, and is a fiber-reinforced composite material made by curing or solidifying the resin contained therein. Furthermore, the fiber-reinforced composite material layer [C] made of prepreg [c]4 is a fiber-reinforced composite material obtained by curing or solidifying the resin of prepreg [c]4.

In the fiber reinforced composite material according to the present invention, the fiber volume content VfA (%) of the fiber reinforced composite material layer [A] and the fiber volume content VfB (%) of the fiber reinforced composite material layer [B] are VfA> It is preferable to have a relationship of VfB. Specifically, it is preferable for VfA to be 50% or more and VfB to be 50% or less from the viewpoint of the design of the fiber-reinforced composite material.

Furthermore, the fiber volume content VfA of the fiber-reinforced composite material layer [A] is preferably 55% or more and 90% or less from the viewpoint of mechanical properties and design of the fiber-reinforced composite material. Preferably it is 60 to 90%, more preferably 60 to 70%. If it is less than 55%, the resin layer of the fiber reinforced composite material layer [A] will increase, making it difficult for air and volatile components to transfer to the fiber reinforced composite material layer [B], which will reduce the design quality of the fiber reinforced composite material. You may not be satisfied.

In the fiber-reinforced composite material according to the present invention, the fiber volume content VfB of the fiber-reinforced composite material layer [B] is preferably 1 to 60% from the viewpoint of impregnating the prepreg, and preferably 5 to 50%. , more preferably 5 to 20%.

Further, the fiber volume content of the fiber-reinforced composite material layer [C] is preferably 55% or more and 90% or less from the viewpoint of mechanical properties and design of the fiber-reinforced composite material. Preferably it is 60 to 90%, more preferably 60 to 70%. If it is less than 55%, the resin layer of the fiber-reinforced composite material layer [C] increases, making it difficult for air and volatile components to transfer to the fiber-reinforced composite material layer [B], and the design aspect of the fiber-reinforced composite material is not satisfactory. There is.

Next, a method for manufacturing a fiber-reinforced composite material according to the present invention will be explained. The method for producing a fiber-reinforced composite material according to the present invention is characterized by having a molding step of heating the prepreg laminate while pressurizing the outside of the prepreg laminate.

In the method for producing a fiber-reinforced composite material according to the present invention, in the molding step of heating the prepreg laminate while applying pressure to the outside of the prepreg laminate, the step of applying pressure to the inside of the prepreg laminate at a pressure of -80 kPa or less (gauge pressure) is performed. Inclusion is preferable from the viewpoint of reducing voids in the resulting fiber-reinforced composite material. The pressure (gauge pressure) inside the prepreg laminate is preferably -90 kPa or less, more preferably -95 kPa or less.

In addition, in the method for producing a fiber reinforced composite material according to the present invention, in the molding step of heating the prepreg laminate and pressurizing the outside of the prepreg laminate, the resin contained in the cut prepreg [a] or the prepreg [c] is It is preferable to impregnate the fiber base material [b] from the viewpoint of improving the design of the resulting fiber-reinforced composite material.

Examples of the method for manufacturing the fiber reinforced composite material of the present invention include press molding using a mold, vacuum bag molding, autoclave molding, and the like.

Applications of the fiber reinforced composite material of the present invention include, for example, personal computers, displays, OA equipment, mobile phones, personal digital assistants, facsimile machines, compact discs, portable MDs, portable radio cassettes, PDAs (electronic notebooks, etc.) Information terminals), video cameras, digital video cameras, optical equipment, audio equipment, air conditioners, lighting equipment, entertainment products, toys, and other home appliances, etc. Electronic equipment parts, parts for civil engineering and building materials such as "pillars, panels, reinforcing materials", "various members, various frames, various hinges, various arms, various axles, various wheel bearings, various beams, propeller shafts, wheels, gears" Suspension, accelerator, or steering parts such as boxes, hoods, roofs, doors, fenders, trunk lids, side panels, rear end panels, upper back panels, front bodies, under bodies, various pillars, various members, various frames, External panels or body parts such as various beams, various supports, various rails, various hinges, etc.'' Exterior parts such as bumpers, bumper beams, moldings, undercovers, engine covers, rectifier plates, spoilers, cowl louvers, aero parts, etc.'' , "Interior parts such as instrument panels, seat frames, door trims, pillar trims, handles, meter visors, various modules, etc.", or "Motor parts, CNG tanks, gasoline tanks, fuel pumps, air intakes, intake manifolds, carburetor main bodies, Structural parts for automobiles and motorcycles such as fuel system, exhaust system, or intake system parts such as carburetor spacers, various piping, and various valves, etc., alternator terminals, alternator connectors, IC regulators, potentiometer bases for light wheels, engines, etc. Cooling water joints, thermostat bases for air conditioners, heating hot air flow control valves, brush holders for radiator motors, turbine vanes, wiper motor related parts, distributors, starter switches, starter relays, window washers nozzles, air conditioner panel switch boards, Fuel-related electromagnetic valve coil, battery tray, AT bracket, headlamp support, pedal housing, protector, horn terminal, step motor rotor, lamp socket, lamp reflector, lamp housing, brake piston, noise shield, spare tire cover, solenoid bobbin , engine oil filters, ignition cases, scuff plates, fascias, etc., motorcycle parts, and aircraft parts such as ``landing gear pods, winglets, spoilers, edges, rudders, elevators, faillings, ribs.'' Examples include parts. From the viewpoint of mechanical properties, it is preferably used for the interior and exterior of automobiles, electrical and electronic equipment casings, bicycles, structural materials for sporting goods, aircraft interior materials, and transportation boxes.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples.

Cut prepreg [a] in which reinforcing fibers are impregnated with resin, fiber base material not impregnated with resin [b], prepreg [c] in which reinforcing fibers of continuous fibers are impregnated with resin, shapeability of prepreg laminates , a method for measuring the fiber volume content of a fiber-reinforced composite material, and a method for measuring the surface quality of a fiber-reinforced composite material are shown below. The production environment and evaluation of prepreg laminates and fiber-reinforced composite materials in Examples were conducted in an atmosphere with a temperature of 25° C.±2° C. and a relative humidity of 50%, unless otherwise specified. Furthermore, the present invention is not limited to these Examples.

<Cut prepreg [a] in which reinforcing fibers are impregnated with resin>
・Incision prepreg A obtained by the following manufacturing method
[Epoxy resin composition]
In a kneading device, 35 parts by mass of "jER" (registered trademark) 4007P (manufactured by Japan Epoxy Resins Co., Ltd.) and 35 parts by mass of liglycidyl-p-aminophenol ("Araldide" (registered trademark) MY0510 (Huntsman Advanced - 3 parts by mass of "Vinylec" (registered trademark) PVF-K to 30 parts by mass of bisphenol F type epoxy resin ("Epicron" (registered trademark) 830 (manufactured by DIC Corporation))) (Polyvinyl formal) (manufactured by Chisso Corporation) was blended to dissolve the thermoplastic resin (PVF-K) into the epoxy resin. Thereafter, 5 parts by mass of dicyandiamide (hardening agent, DICY-7, manufactured by Mitsubishi Chemical Corporation) as a hardening agent, and further DCMU99 (3-(3,4-dichlorophenyl)-1,1-dimethyl) as a hardening agent. Three parts by mass of urea and a curing accelerator (manufactured by Hodogaya Chemical Industry Co., Ltd.) were kneaded to prepare an epoxy resin composition.

[Carbon fiber]
・“Trading Card (registered trademark)” T700S-12K (manufactured by Toray Industries, Inc.)
[Incision prepreg [a]]
The prepared epoxy resin composition was applied onto release paper using a knife coater to produce two resin films each weighing 52 g/m ² . Next, the resin film obtained as described above was laminated on both sides of sheet-shaped carbon fibers arranged in one direction, and after impregnating with resin by heating and pressing, the basis weight of the carbon fibers was 190 g/m. A unidirectional prepreg having a matrix resin mass fraction of 35.4%, a prepreg basis weight of 294 g/m ² , and a prepreg thickness of 189 μm was prepared using Example No. ² .

Next, the obtained unidirectional prepreg sheet was inserted in the fiber direction into a roller cutter having a blade arranged in a cylinder, and intermittent linear cuts were inserted in the cut pattern shown in FIG. 4. The fiber length L was 24 mm, θ was ±14°, and the projected length Ws of the cut in the plane of the prepreg in the vertical direction of the reinforcing fibers was 0.25 mm. The same number of +14° cuts and −14° cuts were inserted into the prepreg of the unidirectional prepreg sheet. For all cuts, the nearest cut with the opposite sign of the cutting angle was the cut with the opposite sign, and there were four cuts with the opposite sign of the cut angle at a closer distance than the adjacent cuts with the same sign of the cutting angle. . Further, there was no adjacent notch within the radius of the notch length Y from any point of the notch. The rows of cuts were arranged with cuts having a cut length Y of 1 mm at a pitch of 1 mm, and the fibers were divided by the cuts corresponding to every other row of cuts to produce a cut prepreg sheet. The distance between adjacent notches on the same straight line was approximately 10 times Y. When the cross section of the release paper after the cut was inserted was observed with an optical microscope, it was found that the cut penetrated up to 40% in the thickness direction of the release paper.

The obtained prepreg was cut into 25 cm square pieces in the 0° direction, stacked in 8 layers with the fiber directions aligned, and heated in an autoclave at a temperature of 130°C for 2 hours under a pressure of 0.5 MPa. A flat plate of fiber-reinforced plastic was produced by molding at a temperature rate of 1.6° C./min. A small piece of 10 mm x 10 mm was cut out from approximately the center of the molded flat plate so as to include the cross section in the direction substantially perpendicular to the fibers, embedded in epoxy resin, and the cross section in the direction substantially perpendicular to the fibers was polished. The polished cross section was magnified 200 times or more using an optical microscope, and a 300 μm×300 μm area was obtained as a 900 pixel×900 pixel digital image. The obtained digital image is binarized so that pixels corresponding to the fiber part are 1 and pixels corresponding to the resin are 0, and from the ratio of the number of pixels corresponding to the fiber part to the total number of pixels of the digital image, the direction approximately perpendicular to the fibers is determined. The area ratio of carbon fiber in the cross section was obtained. Since the carbon fibers were arranged in one direction in the longitudinal direction, the area ratio was regarded as the volume content ratio Vf of the carbon fibers. A total of 10 digital images were taken at random from the two pieces so that the areas did not overlap, and the average value of the carbon fiber volume content Vf was calculated to be 56%.

<Fiber base material not impregnated with resin [b]>
・Fiber base material A: "Torayca (registered trademark)" CO6151B (manufactured by Toray Industries, Inc.) (area weight: 92 g/m ² , thickness: 0.11 mm)
・Fiber base material B: Surface mat, FC-30S (manufactured by Central Glass Fiber Co., Ltd.) (Area weight: 30 g/m ² , Thickness: 0.23 mm)

<Prepreg [c] in which reinforcing continuous fibers are impregnated with resin>
・Prepreg C obtained by the following manufacturing method
[Epoxy resin composition]
In a kneading device, 35 parts by mass of "jER" (registered trademark) 4007P (manufactured by Japan Epoxy Resins Co., Ltd.) and 35 parts by mass of liglycidyl-p-aminophenol ("Araldide" (registered trademark) MY0510 (Huntsman Advanced - 3 parts by mass of "Vinylec" (registered trademark) PVF-K to 30 parts by mass of bisphenol F type epoxy resin ("Epicron" (registered trademark) 830 (manufactured by DIC Corporation))) (Polyvinyl formal) (manufactured by Chisso Corporation) was blended to dissolve the thermoplastic resin (PVF-K) into the epoxy resin. Thereafter, 5 parts by mass of dicyandiamide (hardening agent, DICY-7, manufactured by Mitsubishi Chemical Corporation) as a hardening agent, and further DCMU99 (3-(3,4-dichlorophenyl)-1,1-dimethyl) as a hardening agent. Three parts by mass of urea and a curing accelerator (manufactured by Hodogaya Chemical Industry Co., Ltd.) were kneaded to prepare an epoxy resin composition.

[Carbon fiber]
・“Trading Card (registered trademark)” T700S-12K (manufactured by Toray Industries, Inc.)
[Prepreg [c]]
The prepared epoxy resin composition was applied onto release paper using a knife coater to produce two resin films each weighing 52 g/m ² . Next, the resin film obtained as described above was laminated on both sides of sheet-shaped carbon fibers arranged in one direction, and after impregnating with resin by heating and pressing, the basis weight of the carbon fibers was 190 g/m. A unidirectional prepreg having a matrix resin mass fraction of 35.4%, a prepreg basis weight of 294 g/m ² , and a prepreg thickness of 189 μm was prepared using Example No. ² .

(1) Shaping property of prepreg laminate A sample measuring 240 mm long x 340 mm wide was cut out from the prepreg laminate, placed in an oven at 60°C for 20 minutes, taken out, and shaped into an iron rectangular parallelepiped measuring 40 mm long x 80 mm wide x 35 mm high. The shapeability on 5 sides of the shape (5 sides other than 1 side of 40 mm long x 80 mm wide) was evaluated.

The criteria for determining the shapeability of prepreg laminates are: ◎ if the cut prepreg or prepreg can be shaped into a rectangular parallelepiped shape without wrinkles or tears, and there is a total of 1 wrinkle or tear in the cut prepreg or prepreg. If wrinkles or tears occurred in two or more places in the cut prepreg or prepreg, the mark was △.

(2) Method for measuring fiber volume content of fiber reinforced composite material The prepreg laminate is molded in an autoclave at a temperature of 130°C for 2 hours under a pressure of 0.5 MPa at a temperature increase rate of 1.6°C/min. Six fiber-reinforced composite materials were produced. A sample measuring 20 mm long x 20 mm wide was cut out from each of these fiber-reinforced composite materials in the in-plane direction perpendicular to the stacking direction, and the cross section was polished and enlarged more than 200 times using a laser microscope (KEYENCE VK-9510). Photographs were taken so that two or more fiber layers were within the field of view. Ten locations were arbitrarily selected for each layer from a similar operation. Each fiber volume content was determined from the thickness of each layer, fiber basis weight, and fiber specific gravity, and the average of 10 locations was taken as the fiber volume content.

(3) Method for measuring surface quality of fiber-reinforced composite material The fiber-reinforced composite material produced in (2) was visually inspected for pinholes on the designed surface. As a criterion, if the number of pinholes was 10 or less, it was rated ◎, if it was 11 or more and 30 or less, it was rated ○, and if it was 31 or more, it was rated △.

(Example 1)
From a design perspective, two layers of cut prepreg A and fiber base material A were laminated in this order to produce a prepreg laminate.

Using the obtained prepreg laminate, the above (1) shapeability of the prepreg laminate, (2) method for measuring the fiber volume content of the fiber reinforced composite material, and (3) measurement of the surface quality of the fiber reinforced composite material were carried out. The method was carried out as described to obtain a fiber-reinforced composite material, and the formability of the prepreg laminate, the fiber volume content of the fiber-reinforced composite material, and the surface quality of the fiber-reinforced composite material were measured. The results are shown in Table 1.

(Examples 2 to 6, Comparative Examples 1 to 4)
A cut prepreg [a] in which reinforcing fibers are impregnated with the resin of the prepreg laminate, a fiber base material not impregnated with resin [b], a prepreg [c] in which reinforcing fibers of continuous fibers are impregnated with resin, and a laminated structure. A prepreg laminate was produced in the same manner as in Example 1 except for the changes shown in Tables 1 and 2. Using the prepared prepreg laminate, the shapeability of the prepreg laminate was measured. Furthermore, a fiber-reinforced composite material was obtained using the prepared prepreg laminate, and the fiber volume content and surface quality were measured. The obtained results are summarized in Tables 1 and 2.

By comparing Examples 1 to 6 and Comparative Examples 1 to 4, the prepreg laminate of the present invention includes a structure including a cut prepreg in which reinforcing fibers are impregnated with resin, and a fiber base material not impregnated with resin. Therefore, when the resin is impregnated from the prepreg placed on the design surface into the unimpregnated fiber base material during molding, the air and volatile components that cause pinholes on the design surface are also removed from the unimpregnated resin. It can be seen that the resulting fiber-reinforced composite material has an excellent design because it is transferred to the base material. Furthermore, since the prepreg laminate is made by laminating cut prepregs, it can be seen that the prepreg laminate has excellent shapeability.

According to the present invention, a fiber-reinforced composite material with excellent prepreg laminate formability and excellent design can be obtained, so it can be used for sports equipment such as tennis rackets and golf shafts, and for automobile exteriors such as bumpers and doors. Automobile structural materials such as chassis and front side members, steering wheels, meter visors, aircraft structural members, windmill blades, automobile exterior materials, automobile interior materials, IC trays and laptop computer housings, etc. It is useful and can be widely used in computer applications.

1 Design surface 2, 2a, 2b Notch prepreg [a]
3 Fiber base material [b]
4 Prepreg [c]
5 Intermittent diagonal cuts (positive angle to fiber direction)
6 Intermittent diagonal cuts (negative angle to the fiber direction)
7 Fiber direction 8 Fiber orthogonal direction 10 Prepreg laminate

Claims (10)

A prepreg in which reinforcing fibers are impregnated with resin on one surface of a fiber base material [b] that is not impregnated with resin, and at least some of the reinforcing fibers are formed by a plurality of cuts to a fiber length (L) . One or more layers of cut prepreg [a] composed of reinforcing fibers of 10 to 300 mm and having a volume content Vf of reinforcing fibers in the range of 45 to 65% are laminated, and the fiber base material [a] is laminated with one or more layers. A prepreg laminate having a sandwich structure in which one or more layers of prepreg [c] in which reinforcing continuous fibers are impregnated with resin are laminated on the other surface of [b]. The prepreg laminate according to claim 1 , wherein at least one surface of the prepreg laminate is a designed surface, and the fiber base material [b] is laminated as the second or third layer from the designed surface side. The prepreg laminate according to claim 1 or 2 , wherein the cut prepreg [a] has a thickness of 30 to 300 μm. The prepreg laminate according to any one of claims 1 to 3 , wherein the reinforcing fibers constituting the cut prepreg [a] are carbon fibers, and the resin is a thermosetting resin. Any one of claims 1 to 4 , wherein the fiber base material [b] contains carbon fibers or glass fibers, the carbon fibers or glass fibers are discontinuous, and have a basis weight of 5 to 100 g/m ² . The prepreg laminate described. Using the prepreg laminate according to any one of claims 1 to 5 , a fiber-reinforced composite material layer [A] derived from the cut prepreg [a] and the cut prepreg [a] or the prepreg [c] ] A fiber-reinforced composite material comprising at least a fiber-reinforced composite material layer [B] derived from the fiber base material [b] containing a resin impregnated with. Claim 6 : The fiber volume content VfA (%) of the fiber reinforced composite material layer [A] and the fiber volume content VfB (%) of the fiber reinforced composite material layer [B] have a relationship of VfA>VfB. Fiber-reinforced composite material described in . A method for producing a fiber-reinforced composite material, comprising a molding step of heating the prepreg laminate according to any one of claims 1 to 5 and applying pressure to the outside of the prepreg laminate. 9. The method for producing a fiber-reinforced composite material according to claim 8 , wherein the molding step further includes a step of applying pressure inside the prepreg laminate at −80 kPa or less (gauge pressure). The method for producing a fiber-reinforced composite material according to claim 8 or 9 , wherein in the molding step, the fiber base material [b] is impregnated with the resin contained in the cut prepreg [a] or the prepreg [c].