JP2021155513A - Prepreg laminate, fiber reinforced composite material, and method for producing fiber reinforced composite material - Google Patents

Abstract

To provide a carbon fiber reinforced composite material that has excellent design surface, and to provide a method for producing fiber reinforced composite material, and a prepreg with excellent shape-forming property suitably used therefor.SOLUTION: Provided is a prepreg laminate, which prepreg is a prepreg made of reinforcing fiber and impregnated with resin, and, by multiple cuts, at least some of the reinforcing fibers are composed of reinforcing fibers having a fiber length (L) of 10 to 300 mm, and the prepreg laminate is a prepreg laminate in which a cut prepreg [a] having a volume content Vf of reinforcing fibers in the range of 45 to 65%, and a fiber substrate [b] not impregnated with resin are laminated.SELECTED DRAWING: Figure 1

Description

The present invention relates to a fiber-reinforced composite material having an excellent design surface, a method for producing the fiber-reinforced composite material, and a prepreg laminate preferably used for the same.

Fiber-reinforced composite materials are useful because they are excellent in strength, rigidity, conductivity, etc., and are useful for aircraft structural members, windmill blades, automobile exterior materials, automobile interior materials, and IC trays and laptop housings ( It is widely deployed in computer applications such as housing), and its demand is increasing year by year.

A fiber-reinforced composite material is a material obtained by molding a prepreg containing reinforcing fibers and a resin as essential components. In that case, air and volatile components remain in the resin portion of the prepreg before and during molding. It is known that the fiber-reinforced composite material obtained is generated with 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 the fiber-reinforced composite material obtained from the prepreg. Further, various techniques have been proposed for the purpose of improving the shapeability and molding robustness of the prepreg.

As one of them, it has been proposed to mold a fiber-reinforced composite material from a prepreg in which reinforcing fibers are impregnated with a resin and a prepreg laminate in which a base material not impregnated with the resin is laminated (see Patent Document 1). ). This technique has been proposed to provide excellent design aspects for fiber reinforced composites. Separately, it is a prepreg having a layer containing reinforcing fibers impregnated with the resin composition, and the content ratio of the resin composition in the prepreg is within a predetermined range, and at least a part thereof has a predetermined fiber length by a plurality of cuts. A technique has been proposed in which a prepreg is provided, which is composed of the reinforcing fibers of the above, has excellent shapeability to a three-dimensional shape, and has excellent molding robustness that suppresses molding defects that cause a decrease in member strength. (See Patent Document 2). Furthermore, by laminating a triaxial woven fabric and a non-woven fabric, it has the same strength, elasticity and high specific strength as a fiber-reinforced composite material, and has conductivity, insulation, thermal conductivity and heat insulation comparable to those of a metal material. A technique for imparting a composite material, a molded product and a prepreg having at least one of the above has been proposed (see Patent Document 3).

However, these technologies provide excellent design aspects of fiber-reinforced composite materials, improve prepreg shapeability and molding robustness, and improve the 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 aspect of the fiber-reinforced composite material.

International Publication 2018/079475 Pamphlet International Publication 2016/0431156 Pamphlet International Publication No. 2002/018127 Pamphlet

An object of the present invention is to provide a carbon fiber reinforced composite material having an excellent design surface, a method for producing the fiber reinforced composite material, and a prepreg laminate having excellent shapeability, which is suitable for the production method.

The present invention has any of the following configurations in order to achieve the above object.

That is, it is a prepreg in which reinforcing fibers are impregnated with a resin, and at least a part of the reinforcing fibers is composed of reinforcing fibers having a fiber length (L) of 10 to 300 mm by a plurality of cuts, and the volume of the reinforcing fibers. It is a prepreg laminate in which a cut prepreg [a] having a content Vf in the range of 45 to 65% and a fiber base material [b] not impregnated with a resin are laminated.

According to a preferred embodiment of the prepreg laminate of the present invention, the prepreg laminate has a sandwich structure in which one layer or a plurality of layers of the cut prepreg [a] are laminated on both sides of the fiber base material [b].

According to a preferred embodiment of the prepreg laminate of the present invention, the cut prepreg [a] is laminated in one layer or a plurality of layers on one surface of the fiber base material [b], and the fiber base material [b] is laminated. It is a prepreg laminated body having a sandwich structure in which one layer or a plurality of layers of prepreg [c] impregnated with resin-impregnated reinforcing fibers of continuous fibers on the other surface.

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

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

According to a preferred embodiment of the prepreg laminate of the present invention, the reinforcing fiber constituting the cut prepreg [a] is a carbon fiber, 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 grain size is 5 to 100 g / m. It is a prepreg laminated body of ^2.

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

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.

Further, the method for producing a fiber-reinforced composite material of the present invention is a method for producing a fiber-reinforced composite material, which comprises a molding step of pressurizing 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 fiber reinforced composite material includes a step of further performing the inside of the prepreg laminate at a pressure of −80 kPa or less (gauge pressure) in the molding step. It is a manufacturing method.

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

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

It is a schematic diagram of the prepreg laminated body which concerns on one actual form of this invention. It is a schematic diagram of the prepreg laminated body which concerns on another actual form of this invention. It is a schematic diagram of the prepreg laminated body which concerns on another actual form of this invention. It is a conceptual diagram which shows an example of the cut pattern of the cut prepreg of this invention.

Hereinafter, embodiments will be described with reference to the drawings. The present invention is not limited to the drawings and the examples.

In the prepreg laminate according to the present invention, as shown in FIG. 1, at least a notched prepreg [a] 2 in which reinforcing fibers are impregnated with resin and a fiber base material [b] 3 not impregnated with resin are laminated. It is important that the prepreg laminate 10 is used. Further, as shown in FIG. 2, a sandwich-structured prepreg laminate in which a cut prepreg [a] 2 in which a reinforcing fiber is impregnated with a resin is laminated on both sides of a fiber base material [b] 3 which is not impregnated with a resin. The body is also preferably used. Further, as shown in FIG. 3, the cut prepreg [a] 2 in which the reinforcing fibers are impregnated with the resin is laminated on one surface of the fiber base material [b] 3 not impregnated with the resin, and the resin is laminated. A prepreg laminated body 10 having a sandwich structure in which prepreg [c] 4 impregnated with reinforcing fibers of continuous 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 is impregnated between the fibers. By laminating the prepreg [a] 2 or the prepreg [c] 4, the fiber base material [b] 3 is impregnated with sufficient resin, so that the prepreg [a] 2 or the prepreg [c] 4 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 at least a reinforcing fiber impregnated with a resin.

The reinforcing fiber used for the notch prepreg [a] 2 is not particularly limited, and for example, metal fibers such as aluminum fiber, brass fiber, and stainless fiber, PAN-based carbon fiber, rayon-based carbon fiber, and lignin-based carbon fiber. , Pitch-based carbon fiber carbon fiber, graphite fiber, insulating fiber such as glass fiber, organic fiber such as aramid fiber, PBO fiber, polyphenylene sulfide fiber, polyester fiber, acrylic fiber, nylon fiber, polyethylene fiber, Examples thereof include inorganic fibers such as silicon carbide fiber and silicon nitride fiber. Further, these fibers may be surface-treated. The surface treatment includes a treatment with a coupling agent, a treatment with a sizing agent, a treatment with a binding agent, a treatment with an additive, and the like, in addition to a treatment with a metal as a conductor. Further, one type of these reinforcing fibers may be used alone, or two or more types may be used in combination.

Among them, carbon fibers such as PAN-based carbon fiber, pitch-based carbon fiber, and rayon-based carbon fiber, which are excellent in specific strength and specific rigidity, are preferably used from the viewpoint of weight reduction effect. Further, from the viewpoint of enhancing the economic efficiency of the obtained laminate, glass fiber is preferably used, and in particular, carbon fiber and glass fiber are preferably used in combination from the viewpoint of the balance between mechanical properties and economic efficiency. Further, from the viewpoint of enhancing the impact absorption and shapeability of the obtained laminate, aramid fibers are preferably used, and in particular, carbon fibers and aramid fibers are preferably used in combination from the viewpoint of the balance between mechanical properties and impact absorption. Further, from the viewpoint of increasing the conductivity of the obtained laminate, reinforcing fibers coated with a metal such as nickel, copper or ytterbium can also be used. Among these, PAN-based carbon fibers having excellent mechanical properties such as strength and elastic modulus can be more preferably used.

The reinforcing fibers used for the cut prepreg [a] 2 adopt the form of a unidirectional base material in which the reinforcing fibers are aligned in one direction, a bidirectional woven fabric, a multi-axis woven fabric, a non-woven fabric material, a mat, a knitted fabric, a braid, or the like. However, it is preferable to use all of them in the form of a fabric-like base material in which reinforcing fibers are continuous. The form of the reinforcing fiber can be freely selected depending on the application and the area of use. Among them, a unidirectional base material in which fibers are arranged in one direction is preferable because the fiber packing is good and Vf can be efficiently improved, so that the mechanical properties can be exhibited to the highest level. The cut prepreg [a] 2 is made by making a cut in a base material composed of the continuous fibers so as to have a fiber length (L). Regarding the fiber length (L), it is important that at least some of the fibers are composed of reinforcing fibers having a thickness of 10 to 300 mm. When the fiber length (L) of the reinforcing fiber is within this range, it is possible to secure the number of gas degassing passes in the out-of-plane direction during molding and effectively suppress bridging. .. When L is 10 mm or more, the distance between the cuts is increased, so when a load is applied to the fiber reinforced plastic molded using such a cut prepreg, cracks are difficult to connect and the strength is high. It becomes. Considering the relationship between the shape followability at the time of molding, the effect of suppressing molding defects such as voids, and the mechanical properties of the molded fiber reinforced plastic, the more preferable range of the fiber length L of the reinforced fiber divided by the cut is It is 10 to 100 mm.

Further, it is important that the volume content Vf of the reinforcing fiber of the cut prepreg [a] 2 is in the range of 45 to 65%. By setting the volume content Vf of the reinforcing fibers to 65% or less, the reinforcing fibers in the cut portion are displaced, bridging is effectively suppressed, and shape followability and molding defects such as voids are suppressed. Can be done. From this point of view, it is more preferable that Vf is 60% or less. Further, the lower the Vf, the more the bridging can be suppressed, but when the Vf is smaller 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 the examples and then processing an image with an optical microscope or a laser microscope.

The resin used for the cut prepreg [a] 2 is not particularly limited, and both a thermosetting resin and a thermoplastic resin can be preferably 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, and melamine resin are preferably used. be able to. For these, a resin or the like in which two or more kinds are blended may be applied. Among these, epoxy resin, phenol resin, and vinyl ester resin are preferable from the viewpoint of mechanical properties and heat resistance of the laminate. In particular, the epoxy resin is more preferable from the viewpoint of the mechanical properties of the laminate, heat resistance, and handleability. The epoxy resin is preferably contained as a main component of the resin to be used in order to exhibit its excellent mechanical properties, and specifically, it is preferably contained in an amount of 60% by weight or more per resin composition.

As the epoxy resin, an epoxy resin having amines, phenols, or a compound having a carbon-carbon double bond as a precursor is preferably used.

As the curing agent for the epoxy resin, any compound having an active group capable of reacting with the epoxy group can be used. As the curing agent, a compound having an amino group, an acid anhydride group and an azido group is suitable. More specifically, as the curing agent, for example, dicyandiamide, various isomers of diaminodiphenylmethane and diaminodiphenylsulfone, aminobenzoic acid esters, various acid anhydrides, phenol novolac resin, cresol novolac resin, polyphenol compound, imidazole derivative. Lewis like carboxylic acid anhydrides such as aliphatic amines, tetramethylguanidine, thiourea addition amines, methylhexahydrophthalic anhydrides, carboxylic acid hydrazides, carboxylic acid amides, polymercaptans and boron trifluoride ethylamine complexes. Acid complexes and the like can be mentioned. These curing agents may be used alone or in combination.

It is also preferable to dissolve the thermoplastic resin in the thermosetting resin and use it. Such thermoplastic resins are generally selected from 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. It is preferably a thermoplastic resin having a bond, but 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, polyaramide resin, polyether nitrile resin and polybenzimidazole resin is dissolved in the thermosetting resin. It is preferable to have.

Examples of the thermoplastic resin 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. Polyarylene sulfide resin such as polyamide resin, polyoxymethylene resin, polyphenylene sulfide resin, polyketone resin, polyether ketone resin, polyether ether ketone resin, polyether ketone ketone resin, polyether nitrile resin, polytetrafluoroethylene resin. Fluorine-based resins such as, crystalline resins such as liquid crystal polymer resins, polystyrene resins, polycarbonate resins, polymethylmethacrylate resins, polyvinyl chloride resins, polyphenylene ether resins, polyimide resins, polyamideimide resins, polyetherimide resins, polysalphon Non-crystalline resins such as resins, polyether sulfone resins, and polyarylate resins, other phenol-based resins, phenoxy resins, and polystyrene resin-based, polyolefin resin-based, polyurethane resin-based, polyester resin-based, polyamide resin-based, and polybutadiene resins. Examples thereof include thermoplastic elastomers such as based, polyisoprene resin-based, fluororesin, and polyacrylonitrile resin-based, and thermoplastic resins selected from these copolymers and modified products. Among them, a polyolefin resin is preferable from the viewpoint of lightness of the obtained laminate, a polyamide resin is preferable from the viewpoint of strength, and a polyester resin is preferably used from the viewpoint of surface appearance.

The thermoplastic resin exemplified in the above group may contain an impact resistance improver such as an elastomer or a rubber component, and other fillers and additives as long as the object of the present invention is not impaired. Examples of these are inorganic fillers, flame retardants, conductivity-imparting agents, crystal nucleating agents, UV absorbers, antioxidants, anti-vibration agents, antibacterial agents, insect repellents, deodorants, anti-coloring agents, heat stabilizers. , Release agent, antistatic agent, plasticizer, lubricant, colorant, pigment, dye, foaming agent, antifoaming agent, or coupling agent.

Further, a filler may be added to a resin such as a thermosetting resin or a thermoplastic resin for use. Fillers include continuous reinforcing fibers, calcium carbonate, talc, silica, clay, glass flakes, catechins, zeolites, silica balloons, glass balloons, silas balloons, carbon black, carbon nanotubes, fullerene, graphite, metal powder, metal foil, etc. 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 can be mentioned. Of these, an intermediate base material containing continuous reinforcing fibers is preferable from the viewpoint of moldability.

The thickness of the notch prepreg [a] is preferably in the range of 30 to 300 μm. As a result, it is possible to improve the moldability of the prepreg laminate 10 and to achieve both the designability of the fiber-reinforced composite material. If the thickness is less than 30 μm, many pinholes may appear on the design surface of the obtained fiber-reinforced composite material, and if the thickness exceeds 300 μm, problems may occur when making a cut in the prepreg. be.

The fiber base material [b] 3 used in the present invention is a base material composed of fibers so that the resin can be easily impregnated.

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

Among them, carbon fibers such as PAN-based carbon fiber, pitch-based carbon fiber, and rayon-based carbon fiber, which are excellent in specific strength and specific rigidity, are preferably used from the viewpoint of weight reduction effect. Further, from the viewpoint of enhancing the economic efficiency of the obtained prepreg laminate, glass fiber is preferably used, and in particular, carbon fiber and glass fiber are preferably used in combination from the viewpoint of the balance between mechanical properties and economic efficiency. Further, from the viewpoint of enhancing the impact absorption and shapeability of the obtained laminate, aramid fibers are preferably used, and in particular, carbon fibers and aramid fibers are preferably used in combination from the viewpoint of the balance between mechanical properties and impact absorption. Further, from the viewpoint of increasing the conductivity of the obtained laminate, reinforcing fibers coated with a metal such as nickel, copper or ytterbium can also be used. Among these, PAN-based carbon fibers having excellent mechanical properties such as strength and elastic modulus, and glass fibers can be more preferably used from the viewpoint of enhancing the economic efficiency of the obtained laminate.

The basis weight of the fiber base material [b] is preferably in the range of 5 to ^{100 g / m 2.} As a result, it is possible to improve the moldability of the prepreg laminate 10 and to achieve both the designability of the fiber-reinforced composite material. It is preferably 5 to 80 g / m ² , and more preferably 5 to 50 g / m ² .

If the grain size is ^{less than 5 g / m 2} , pinholes may increase on the design surface 1 of ^{the obtained fiber-reinforced composite material, and if it exceeds 100 g / m 2} , the impregnation property of the obtained fiber-reinforced composite material may increase. Problems may occur.

The fiber base material [b] 3 may be any material that is not impregnated with a resin, and examples thereof include non-woven fabrics, woven fabrics, knits, and mats, which are discontinuous fibers in terms of resin impregnation. Is preferable.

The thickness of the fiber base material [b] 3 is preferably in the range of 0.1 to 1.5 mm. As a result, it is possible to achieve both the impregnation property of the fiber base material [b] 3 and the design property of the fiber reinforced composite material. It is preferably 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 obtained fiber-reinforced composite material, and if it exceeds 1.5 mm, there may be a problem with the impregnation property of the obtained fiber-reinforced composite material. There is.

The prepreg [c] obtained by impregnating the reinforcing fibers of continuous fibers with the resin used in the present invention preferably contains at least the reinforcing fibers and the resin.

The reinforcing fiber used for the prepreg [c] is not particularly limited, and the same reinforcing fiber as described in the cut prepreg [a] is used.

The form of the reinforcing fibers is a continuous form, and it is preferable that the reinforcing fibers are in the form of continuous fibers such as long fibers, woven fabrics, tow and roving aligned in one direction.

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 to the second or third layer from the outermost layer on the design surface 1 side. Is preferable.

As a configuration in which the fiber base material [b] 3 is laminated on the second layer from the outermost layer on the design surface 1 side, as shown in FIG. 1, the cut prepreg [a] 2 is laminated from the design surface 1, and then the fiber base material. By forming the prepreg laminate 10 in which [b] 3 is arranged, the fiber base material [b] 3 is impregnated with the air and volatile components of the cut prepreg [a] 2 which is the design surface 1 so that the fiber base material [b] 3 is fiber-reinforced. It is preferable in that an excellent design surface of the composite material can be obtained.

Further, as a preferable laminating mode of the prepreg laminated body 10, as shown in FIG. 2, the cut prepreg [a] 2b is arranged from the design surface 1, then the fiber base material [b] 3 and the cut prepreg [a] 2a are arranged. The prepreg laminated body 10 can be used. With such a laminated structure, the laminating process is not complicated, and the fiber base material [b] 3 is impregnated with the air and volatile components of the cut prepreg [a] 2 which is the design surface 1 together with the resin. , It is preferable in that an excellent design surface 1 of the fiber-reinforced composite material can be obtained. It is also preferable that a plurality of cut prepregs [a] 2a and cut prepregs [a] 2b are laminated.

Further, as another preferable laminating mode of the prepreg laminated body 10, as shown in FIG. 3, the prepreg laminated body 10 is further provided with the cut prepreg [a] 2, then the fiber base material [b] 3, and the prepreg [c] 4. The arranged prepreg laminate 10 can also be preferably used. It is also preferable to stack a plurality of cut prepregs [a] 2 and prepregs [c] 4.

The fiber-reinforced composite material of the present invention comprises 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 the cut prepreg [a] or the prepreg [c]. It is preferable that the fiber-reinforced composite material contains at least the fiber-reinforced composite material layer [B] derived from the fiber base material [b] containing the resin impregnated in. When laminating a prepreg [c] in which a reinforcing fiber of a continuous fiber is impregnated with a resin, a fiber-reinforced composite material layer [C] composed of a prepreg [c] in which the reinforcing fiber of the continuous fiber is impregnated with a resin may be included. can.

When a plurality of layers of the cut prepreg [a] 2, the fiber base material [b] 3 or the prepreg [c] 4 constituting the prepreg laminate 10 are laminated, the fiber type, resin type, fiber volume content, prepreg texture, etc. A combination of a notched prepreg [a] 2, a fiber base material [b] 3 or a prepreg [c] 4 having different textures of reinforcing fibers, prepreg thickness, etc. may be used. In that case, the prepreg laminate 10 can be designed according to 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. Is. Further, the fiber-reinforced composite material layer [B] derived from the fiber base material [b] 3 is a fiber base material [b] containing a resin impregnated in the cut prepreg [a] 2 or the prepreg [c] 4. 3 is a fiber-reinforced composite material obtained by curing or solidifying the contained resin. Further, the fiber-reinforced composite material layer [C] composed of the prepreg [c] 4 is a fiber-reinforced composite material obtained by curing or solidifying the resin of the 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 VfB relationship. Specifically, it is preferable that VfA is 50% or more and VfB is 50% or less from the viewpoint of designability of the fiber-reinforced composite material.

Further, the fiber volume content VfA of the fiber-reinforced composite material layer [A] is preferably 55% or more and 90% or less, respectively, from the viewpoint of mechanical properties and designability of the fiber-reinforced composite material. It is preferably 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] increases, and it becomes difficult for air and volatile components to move to the fiber-reinforced composite material layer [B], which improves the design 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 impregnation property of the prepreg, preferably 5 to 50%. , More preferably 5 to 20%.

The fiber volume content of the fiber-reinforced composite material layer [C] is preferably 55% or more and 90% or less, respectively, from the viewpoint of mechanical properties and designability of the fiber-reinforced composite material. It is preferably 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, and it becomes difficult for air and volatile components to move to the fiber-reinforced composite material layer [B], and the design aspect of the fiber-reinforced composite material is not satisfied. There is.

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

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

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

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

Applications of the fiber-reinforced composite material of the present invention include, for example, "personal computer, display, OA device, mobile phone, mobile information terminal, facsimile, compact disk, portable MD, portable radio cassette, PDA (portable such as electronic notebook). Electricity such as housings, trays, chassis, interior parts, or their cases for information terminals), video cameras, digital video cameras, optical equipment, audio equipment, air conditioners, lighting equipment, entertainment products, toy products, and other home appliances. Electronic equipment parts, civil engineering such as "supports, panels, reinforcements", parts for building 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, "hood, roof, door, fender, trunk lid, side panel, rear end panel, upper back panel, front body, underbody, various pillars, various members, various frames, "Outer panels or body parts such as various beams, various supports, various rails, various hinges", "Exterior parts such as bumpers, bumper beams, moldings, undercovers, engine covers, straightening vanes, spoilers, cowl louvers, aero parts" , "Interior parts such as instrument panels, seat frames, door trims, pillar trims, handles, meter visors, various modules", or "motor parts, CNG tanks, gasoline tanks, fuel pumps, air intakes, intake manifolds, carburetor main bodies," Automotive and motorcycle structural parts such as carburetor spacers, various pipes, various valves and other fuel systems, exhaust systems, or intake system parts, "Others, alternator terminals, alternator connectors, IC regulators, potentiometer bases for light diers, engines" Cooling water joint, thermostat base for air conditioner, heating hot air flow control valve, brush holder for radiator motor, turbine vane, wiper motor related parts, distributor, starter switch, starter relay, window washer nozzle, air conditioner panel switch board, Fuel-related electromagnetic valve coil, battery tray, AT bracket, head lamp 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 filter, ignition device case, scuff plate, facer, etc., automobile parts, motorcycle parts, "landing gear" Aircraft parts such as pods, winglets, spoilers, edges, rudder, elevators, failings, ribs. From the viewpoint of mechanical properties, it is preferably used for interior / exterior of automobiles, housings of electric / electronic devices, bicycles, structural materials for sports equipment, aircraft interior materials, and boxes for transportation.

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

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

<Incision prepreg [a] in which reinforcing fibers are impregnated with resin>
-Cut 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 Resin Co., Ltd.) and 35 parts by mass of ligricidyl-p-aminophenol ("Araldide" (registered trademark) MY0510 (Huntsman Advanced) (Manufactured by Materials)) and 30 parts by mass of bisphenol F type epoxy resin (“Epiclon” (registered trademark) 830 (manufactured by DIC Co., Ltd.)) and 3 parts by mass of “Vinirec” (registered trademark) PVF-K (Polyvinylformal) (manufactured by Chisso Co., Ltd.)) was blended to dissolve a thermoplastic resin (PVF-K) in an epoxy resin. After that, 5 parts by mass of dicyandiamide (curing agent, DICY-7, manufactured by Mitsubishi Chemical Corporation), which is a curing agent, and DCMU99 (3- (3,4-dichlorophenyl) -1,1-dimethyl), which is a curing aid, are added. An epoxy resin composition was prepared by kneading 3 parts by mass of urea and a curing accelerator (manufactured by Hodogaya Chemical Corporation).

[Carbon fiber]
・ "Trading Card (registered trademark)" T700S-12K (manufactured by Toray Industries, Inc.)
[Cut prepreg [a]]
The prepared epoxy resin composition was applied onto a paper pattern using a knife coater to ^{prepare two} 52 g / m 2 resin films. Next, the resin film obtained as described above was laminated on both sides of the sheet-shaped carbon fibers arranged in one direction, impregnated with the resin by heating and pressurizing, and then the carbon fibers had a grain size of 190 g / m. ^{In No. 2} , a unidirectional prepreg having a matrix resin mass fraction of 35.4%, a prepreg texture of 294 g / m 2, and a prepreg thickness of 189 μm was prepared.

Next, the unidirectional prepreg sheet obtained in a roller cutter having a blade arranged in a cylinder was inserted in the fiber direction, and intermittent linear cuts were made with the cut pattern of FIG. The fiber length L was 24 mm, θ was ± 14 °, and the projected length Ws of the reinforcing fibers projected in the plane of the cut prepreg in the vertical direction was 0.25 mm. The same number of + 14 ° cuts and -14 ° cuts were inserted into the prepregs of the one-way prepreg sheet. For all cuts, the cuts with opposite positive and negative cut angles were the closest, and there were cuts with the opposite positive and negative cut angles at a distance closer than the close cuts with the same sign. .. Also, there were no close cuts within the radius of the cut length Y from all points of the cut. The rows of cuts were arranged with cuts having a cut length of Y1 mm at a pitch of 1 mm, and the fibers were divided by the cuts corresponding to every other row of cuts to prepare a cut prepreg sheet. The distance between adjacent cuts on the same straight line was about 10 times that of Y. When the cross section of the release paper after the cut was inserted was observed with an optical microscope, the cut penetrated up to 40% in the thickness direction of the release paper.

The obtained cut prepreg was cut into a size of 25 cm square in the 0 ° direction, 8 layers were laminated in the same fiber direction, and ascended 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 × 10 mm was cut out from the substantially center of the molded flat plate so as to include the cross section in the direction perpendicular to the fiber, embedded with epoxy resin, and the cross section in the direction perpendicular to the fiber was polished. The polished cross section was magnified 200 times or more by an optical microscope, and a region of 300 μm × 300 μm was acquired as a digital image of 900 pixels × 900 pixels. In the obtained digital image, the pixel corresponding to the fiber part is binarized to 1 and the pixel corresponding to the resin is 0, and the ratio of the number of pixels corresponding to the fiber part to the total number of pixels of the digital image is approximately in the direction perpendicular to the fiber. The area ratio of carbon fibers in the cross section was obtained. Since the carbon fibers are 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 randomly obtained from the two small pieces so that the regions did not overlap, and the average value of the volume content Vf of the carbon fibers was calculated to be 56%.

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

<Prepreg [c] impregnated with resin-impregnated reinforcing fibers of continuous fibers>
-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 Resin Co., Ltd.) and 35 parts by mass of ligricidyl-p-aminophenol ("Araldide" (registered trademark) MY0510 (Huntsman Advanced) (Manufactured by Materials)) and 30 parts by mass of bisphenol F type epoxy resin (“Epiclon” (registered trademark) 830 (manufactured by DIC Co., Ltd.)) and 3 parts by mass of “Vinirec” (registered trademark) PVF-K (Polyvinylformal) (manufactured by Chisso Co., Ltd.)) was blended to dissolve a thermoplastic resin (PVF-K) in an epoxy resin. After that, 5 parts by mass of dicyandiamide (curing agent, DICY-7, manufactured by Mitsubishi Chemical Corporation), which is a curing agent, and DCMU99 (3- (3,4-dichlorophenyl) -1,1-dimethyl), which is a curing aid, are added. An epoxy resin composition was prepared by kneading 3 parts by mass of urea and a curing accelerator (manufactured by Hodogaya Chemical Corporation).

[Carbon fiber]
・ "Trading Card (registered trademark)" T700S-12K (manufactured by Toray Industries, Inc.)
[Prepreg [c]]
The prepared epoxy resin composition was applied onto a paper pattern using a knife coater to ^{prepare two} 52 g / m 2 resin films. Next, the resin film obtained as described above was laminated on both sides of the sheet-shaped carbon fibers arranged in one direction, impregnated with the resin by heating and pressurizing, and then the carbon fibers had a grain size of 190 g / m. ^{In No. 2} , a unidirectional prepreg having a matrix resin mass fraction of 35.4%, a prepreg texture of 294 g / m 2, and a prepreg thickness of 189 μm was prepared.

(1) Shapeability of prepreg laminate A sample of 240 mm in length × 340 mm in width is cut out from the prepreg laminate, placed in an oven at 60 ° C. for 20 minutes, and then taken out, and is an iron rectangular parallelepiped of 40 mm in length × 80 mm in width × 35 mm in height. The shapeability of the shape on five surfaces (five surfaces other than one surface of 40 mm in length × 80 mm in width) was evaluated.

As a criterion for determining the shapeability of the prepreg laminate, if the cut prepreg or prepreg can be shaped without wrinkles or tears in a rectangular shape, ◎, the cut prepreg or prepreg has a total of 1 wrinkle or tear. When it occurred in, it was marked as ◯, and when wrinkles or tears occurred in a total of two or more places in the cut prepreg or prepreg, it was marked as Δ.

(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 and a heating rate of 1.6 ° C./min. To prepare 6 fiber-reinforced composite materials. From each of these fiber-reinforced composite materials, a sample of 20 mm in length × 20 mm in width is cut out in the in-plane direction perpendicular to the laminating direction, the cross section is polished, and then magnified 200 times or more with a laser microscope (KEYENCE VK-9510). The photograph was taken so that two or more layers of fibers and a layer of fibers were within the field of view. From the same operation, 10 places were arbitrarily selected for each layer. The volume content of each fiber was obtained from the thickness of each layer, the basis weight of the fiber, and the specific gravity of the fiber, and the average of 10 points 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 design surface. As the judgment criteria, ⊚ was given when the number of pinholes was 10 or less, ◯ was given when 11 or more and 30 or less, and Δ was given when 31 or more.

(Example 1)
Two layers were laminated in the order of the cut prepreg A and the fiber base material A from the design surface to prepare a prepreg laminate.

Using the obtained prepreg laminate, the above-mentioned (1) shapeability of the prepreg composite, (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. The method was carried out as described to obtain a fiber-reinforced composite, and the shapeability of the prepreg composite, the fiber volume content of the fiber-reinforced composite, and the surface quality of the fiber-reinforced composite 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 [b] in which the resin is not impregnated, a prepreg [c] in which the reinforcing fibers of continuous fibers are impregnated with the resin, and a laminated structure are formed. A prepreg laminated body was produced in the same manner as in Example 1 except that the changes were made as shown in Tables 1 and 2. The shapeability of the prepared prepreg laminate was measured using the prepared prepreg laminate. Further, using the prepared prepreg laminate, a fiber-reinforced composite material was obtained, and the fiber volume content and surface quality were measured. The results obtained are summarized in Tables 1 and 2.

By comparison between Examples 1 to 6 and Comparative Examples 1 to 4, the prepreg laminate of the present invention includes a cut prepreg in which a reinforcing fiber is impregnated with a resin, and a fiber base material in which the resin is not impregnated. When the resin is impregnated into the fiber base material that is not impregnated with the resin from the prepreg placed on the design surface during molding, the air and volatile components that cause pinholes on the design surface are also not impregnated with the resin. Since it is transferred to the base material, it can be seen that the obtained fiber-reinforced composite material realizes an excellent design surface. Further, since the prepreg laminate is laminated with the cut prepreg, it can be seen that the prepreg laminate is excellent in shapeability.

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

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

Claims (12)

A prepreg in which reinforcing fibers are impregnated with a resin, in which at least a part of the reinforcing fibers is composed of reinforcing fibers having a fiber length (L) of 10 to 300 mm by a plurality of cuts, and the volume content of the reinforcing fibers is high. A prepreg laminate in which a cut prepreg [a] having a Vf in the range of 45 to 65% and a fiber base material [b] not impregnated with a resin are laminated. The prepreg laminate according to claim 1, which has a sandwich structure in which one layer or a plurality of layers of the cut prepreg [a] are laminated on both sides of the fiber base material [b]. One layer or a plurality of layers of the cut prepreg [a] are laminated on one surface of the fiber base material [b], and the resin is impregnated into the reinforcing fibers of the continuous fiber on the other surface of the fiber base material [b]. The prepreg laminated body according to claim 1, which has a sandwich structure in which one layer or a plurality of layers of the prepreg [c] are laminated. 7. Prepreg laminate. The prepreg laminate according to any one of claims 1 to 4, wherein the cut prepreg [a] has a thickness of 30 to 300 μm. The prepreg laminate according to any one of claims 1 to 5, wherein the reinforcing fibers constituting the cut prepreg [a] are carbon fibers, and the resin is a thermosetting resin. One of claims 1 to 6, wherein the fiber base material [b] contains carbon fibers or glass fibers, the carbon fibers or glass fibers are discontinuous, and the grain size is 5 to 100 g / m ^2. The prepreg laminate according to the description. Using the prepreg laminate according to any one of claims 1 to 7, the fiber-reinforced composite material layer [A] derived from the cut prepreg [a] and the cut prepreg [a] or the prepreg [c] are used. ], A fiber-reinforced composite material containing at least a fiber-reinforced composite material layer [B] derived from the fiber base material [b] containing the resin impregnated in. 8. Claim 8 in which 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, which comprises a molding step of pressurizing the outside of the prepreg laminate while heating the prepreg laminate according to any one of claims 1 to 7. The method for producing a fiber-reinforced composite material according to claim 10, further comprising a step of performing the inside of the prepreg laminate at a pressure of −80 kPa or less (gauge pressure) in the molding step. The method for producing a fiber-reinforced composite material according to claim 10 or 11, 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].

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