JP2021172564A - Method for producing carbon fiber-reinforced silicon carbide-based composite material, and carbon fiber-reinforced silicon carbide-based composite material - Google Patents

Abstract

To provide a method for producing a carbon fiber-reinforced silicon carbide-based composite material, capable of producing the carbon fiber-reinforced silicon carbide-based composite material that is excellent in moldability, has high mechanical strength, and is excellent in thermal conductivity; and to provide a carbon fiber-reinforced silicon carbide-based composite material.SOLUTION: A method for producing a carbon fiber-reinforced silicon carbide-based composite material includes: molding a carbon fiber-reinforced plastic using a sheet molding compound that comprises a carbon fiber and a matrix resin; calcinating the carbon fiber-reinforced plastic to make a carbon fiber-reinforced carbon composite material; and melt-impregnating a metal Si to the carbon fiber-reinforced carbon composite material. In the carbon fiber-reinforced silicon carbide-based composite material, a cross-section obtained by cutting the composite material in a pressure direction at the time of molding has stripe-shaped impregnated parts comprising one or both of the metal Si and silicon carbide, and the stripes in the stripe-shaped impregnated parts are stretched in a random direction.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing a carbon fiber-reinforced silicon carbide-based composite material and a carbon fiber-reinforced silicon carbide-based composite material.

Carbon fiber reinforced carbon composite material (hereinafter, also referred to as "C / C composite material") has excellent heat resistance and heat impact resistance, and is high in strength and light weight, so that it is used for brake discs, brake pads, etc. for aircraft and automobiles. (For example, Patent Document 1). However, since the carbon material is generally oxidized from about 500 ° C., it cannot be used in a high temperature atmosphere except when it is used for a very short time.

As a method of preventing deterioration of physical and chemical properties due to oxidation of the C / C composite material, the C / C composite material is melt-impregnated with metallic Si, and carbon in the composite material is reacted with the metallic Si to cause silicon carbide. It has been converted into a carbon fiber reinforced silicon carbide-based composite material (hereinafter, also referred to as "SiC-C / C composite material").

As a method for producing a SiC-C / C composite material, a method is known in which a laminate of sheets impregnated with a matrix resin is formed on a non-woven fabric, and metallic Si is melt-impregnated after firing. For example, there is a method in which a sheet obtained by entwining defibrated carbon short fibers is laminated, impregnated with resin or pitch, and fired after molding to melt-impregnate metallic Si (Patent Document 2).

A method of blending a raw material other than carbon fiber and then pressure-molding the blended composition mixed with carbon fiber into a predetermined shape in a mold to obtain a SiC-C / C composite material is also known (Patent Document). 3).

Japanese Unexamined Patent Publication No. 7-33543 Japanese Unexamined Patent Publication No. 2007-39319 JP-A-2009-227565

However, in the method of Patent Document 2, the fluidity of the material at the time of molding is poor, and it is difficult to mold into a desired shape. Therefore, for example, it is necessary to make a hole in the C / C composite material after firing, which tends to complicate the production and is disadvantageous in terms of cost. Further, it is difficult to obtain a SiC-C / C composite material having a high thermal conductivity in the thickness direction, and it cannot be said that the characteristics when applied to a brake disc, a brake pad, or the like are sufficient.
Further, since the method of Patent Document 3 needs to use a short carbon fiber having a fiber length of 6 mm, the reinforcing effect of the obtained SiC-C / C composite material by the carbon fiber is not sufficient.

INDUSTRIAL APPLICABILITY The present invention relates to a method for producing a SiC-C / C composite material capable of producing a SiC-C / C composite material having excellent productivity, reduction of processing cost, high mechanical strength, and excellent thermal conductivity, and a SiC-C composite material. It is an object of the present invention to provide a / C composite material.

The present invention has the following aspects.
[1] A carbon fiber reinforced plastic is molded using a sheet molding compound (hereinafter, also referred to as “SMC”) containing a carbon fiber and a matrix resin, and the carbon fiber reinforced plastic is fired to obtain C. A method for producing a SiC-C / C composite material, which comprises a / C composite material and melt-impregnates the C / C composite material with metallic Si.
[2] The method for producing a SiC-C / C composite material according to [1], wherein the carbon fibers are pitch-based carbon fibers.
[3] The method for producing a SiC-C / C composite material according to [1] or [2], wherein the average fiber length of the carbon fibers is 10 mm or more and 60 mm or less.
[4] The method for producing a SiC-C / C composite material according to any one of [1] to [3], wherein the matrix resin is a phenol resin.
[5] The method for producing a SiC-C / C composite material according to any one of [1] to [4], wherein the FAW of the SMC is 200 g / m ² or more and 2000 g / m ^{2 or less.}
[6] Production of the SiC-C / C composite material according to any one of [1] to [5], wherein the carbon fiber content per volume of the carbon fiber reinforced plastic is 20% by volume or more and 60% by volume or less. Method.
[7] The method for producing a SiC-C / C composite material according to any one of [1] to [6], wherein molding using the SMC is performed by a hot press method.
[8] The method for producing a SiC-C / C composite material according to any one of [1] to [7], wherein the carbon fiber reinforced plastic is fired in an inert gas atmosphere.
[9] The method for producing a SiC-C / C composite material according to any one of [1] to [8], wherein the impurity content of the metallic Si is 1.5% by mass or less.
[10] Production of the SiC-C / C composite material according to any one of [1] to [9], wherein the C / C composite material is melt-impregnated with metallic Si at 1400 ° C. or higher and 2000 ° C. or lower under vacuum conditions. Method.
[11] There is a streak-like impregnated portion containing either one or both of metallic Si and silicon carbide in the cross section cut in the pressurizing direction at the time of molding, and the streak direction of the streak-like impregnated portion becomes random. SiC-C / C composite material.
[12] The SiC-C / C composite material according to [11], wherein the contained carbon fibers are pitch-based carbon fibers.

According to the present invention, a method for producing a SiC-C / C composite material capable of producing a SiC-C / C composite material having excellent productivity, reduction in processing cost, high mechanical strength, and excellent thermal conductivity, and SiC. -C / C composites can be provided.

It is an image which observed the cross section cut in the thickness direction (pressurizing direction at the time of molding) of the SiC-C / C composite material of Example 1.

[Manufacturing method of carbon fiber reinforced silicon carbide composite material]
Hereinafter, a method for producing the carbon fiber reinforced silicon carbide-based composite material (SiC-C / C composite material) of the present invention will be described. However, what is described below is an example of an embodiment of the present invention, and the present invention is not limited to the following description as long as the gist thereof is not exceeded.

The method for producing a SiC-C / C composite material of the present invention is a method including the following molding step, firing step, and melt impregnation step.
Molding step: A carbon fiber reinforced plastic (hereinafter, also referred to as “CFRP”) is molded using a sheet molding compound (SMC) containing carbon fiber and a matrix resin.
Firing step: The CFRP is calcined to obtain a C / C composite material.
Melt impregnation step: The C / C composite material is melt-impregnated with metallic Si to obtain a SiC-C / C composite material.

(Molding process)
By molding with SMC, CFRP shaped into a desired shape is obtained. In addition, "formation" means to give a desired shape by deformation without scraping a material such as SMC. The shape and dimensions of CFRP may be appropriately set according to the intended use.

Molding using the SMC is preferably performed by a hot press method from the viewpoint of thermosetting the SMC in a state where the SMC is distributed inside the mold by applying pressure to the SMC. For example, SMC is filled in a mold and pressure-molded to obtain CFRP.
The molding temperature is preferably 130 ° C. or higher and 300 ° C. or lower, and more preferably 150 ° C. or higher and 250 ° C. or lower.

The carbon fiber content Vf per volume of CFRP is preferably 20% by volume or more and 60% by volume or less, and more preferably 30% by volume or more and 50% by volume or less. When Vf is equal to or higher than the lower limit of the above range, a reinforcing effect can be easily obtained, and a SiC-C / C composite material having high mechanical strength can be easily obtained.
Vf can be adjusted by the pressure at the time of molding. For example, when molding is performed at a high pressure, Vf tends to increase. On the contrary, when molding is performed at a low pressure, Vf tends to be small.

The SMC used for molding contains carbon fibers and a matrix resin.

The carbon fiber is not particularly limited, and examples thereof include pitch-based carbon fiber and polyacrylonitrile (PAN) -based carbon fiber. Among them, pitch-based carbon fibers are preferable because of their excellent thermal conductivity and low reactivity with metallic Si.

Pitch-based carbon fibers are obtained by melt-spinning the raw material pitch to obtain pitch fibers, and then insolubilizing, carbonizing, or further graphitizing. Examples of the form of the pitch-based carbon fibers include tows, strands, rovings, and yarns composed of a plurality of single fibers, and short fibers obtained by cutting these are preferable.
The number of filaments of the carbon fiber is preferably 1000 or more and 50,000 or less, and more preferably 6000 or more and 24,000 or less.

The average fiber length of the carbon fibers is preferably 10 mm or more and 60 mm or less, and more preferably 12 mm or more and 30 mm or less. When the average fiber length of the carbon fibers is at least the lower limit of the above range, excellent rigidity can be easily obtained. When the average fiber length of the carbon fibers is not more than the upper limit of the above range, excellent fluidity can be easily obtained at the time of molding.
The average fiber length of the carbon fibers is a value obtained by the following measuring method. The resin in the composite material is burned off to take out only the carbon fibers, and the fiber length of the carbon fibers is measured with a caliper or the like. Measurements are made on 100 randomly selected carbon fibers and the fiber length is calculated as their mass average.

The FAW (fiber mass per unit area) of SMC at the time of molding ^{is preferably 200 g / m 2} or more and 2000 g / m ² or less, more preferably 250 g / m ² or more and 1500 g / m ² or less, and 500 g / m ² or more and 1000 g / m. More preferably, m ^{2 or less.} If the FAW of SMC is equal to or higher than the lower limit of the above range, the productivity is improved. When FAW of SMC is not more than the upper limit of the above range, the impregnation property of the resin is excellent.

The matrix resin may be a thermoplastic resin or a thermosetting resin. As the matrix resin, a thermosetting resin is preferable because a SiC-C / C composite material having high mechanical strength can be easily obtained.

The thermosetting resin is not particularly limited, and examples thereof include epoxy resin, phenol resin, unsaturated polyester resin, urethane resin, urea resin, melamine resin, and imide resin. Among them, epoxy resin, phenol resin, unsaturated polyester resin, and imide resin are preferable as the thermosetting resin from the viewpoint that a SiC-C / C composite material having excellent mechanical strength can be easily obtained. Further, a phenol resin is more preferable because it has a high ratio of carbonizing without being burnt during firing. As the thermosetting resin, one type may be used alone, or two or more types may be used in combination.

Examples of the phenol resin include a resol type phenol resin and a novolak type phenol resin. The resole-type phenol resin is not particularly limited, and a known resin obtained by reacting phenols with aldehydes using a basic catalyst can be used. The novolak type phenol resin is not particularly limited, and a known one obtained by reacting phenols and aldehydes with an acidic catalyst can be used.
The number average molecular weight of the resole-type phenol resin is preferably 300 to 800. The number average molecular weight of the novolak type phenol resin is preferably 500 to 1500.

The phenols are not particularly limited, and for example, phenol, cresol (o-cresol, m-cresol, p-cresol, etc.), xylenol (2,3-xylenol, 2,4-xylenol, 2,5-xylenol, etc.), 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, etc.), ethylphenol (o-ethylphenol, m-ethylphenol, p-ethylphenol, etc.); butylphenol (isopropylphenol, butylphenol, p-tert, etc.) -Butylphenol, etc.), Alkylphenol (p-tert-amylphenol, p-octylphenol, p-nonylphenol, p-cumylphenol, etc.), halogenated phenol (fluorophenol, chlorophenol, bromophenol, iodophenol, etc.), monovalent Phenol substituents (p-phenylphenol, aminophenol, nitrophenol, dinitrophenol, trinitrophenol, etc.), monovalent naphthols (1-naphthol, 2-naphthol, etc.), polyhydric phenols (resorcin, alkylresorcin, etc.) , Pyrogalol, catechol, alkylcatechol, hydroquinone, alkylhydroquinone, fluoroglusin, bisphenol A, bisphenol F, bisphenol S, dihydroxynaphthalin, etc.) and the like.

The aldehydes are not particularly limited, and for example, formaldehyde, paraformaldehyde, trioxane, acetaldehyde, propionaldehyde, polyoxymethylene, chloral, hexamethylenetetramine, furfural, glioxal, n-butylaldehyde, caproaldehyde, allylaldehyde, etc. Examples thereof include benzaldehyde, crotonaldehyde, acrolein, tetraoxymethylene, phenylacetaldehyde, o-tolualdehyde, salicylaldehyde and the like.

The basic catalyst is not particularly limited, and is, for example, an alkali metal hydroxide (sodium hydroxide, lithium hydroxide, potassium hydroxide, etc.), aqueous ammonia, a tertiary amine (triethylamine, etc.), tetramethyl hydroxide. Examples thereof include oxides and hydroxides of ammonium and alkaline earth metals (calcium, magnesium, barium, etc.), alkaline substances (sodium carbonate, hexamethylenetetramine, etc.) and the like.

The acidic catalyst is not particularly limited, and examples thereof include organic carboxylic acids (such as oxalic acid), organic sulfonic acids (such as paratoluene sulfonic acid and phenol sulfonic acid), and mineral acids (such as hydrochloric acid, sulfuric acid, and phosphoric acid). Be done.

Since the viscosity is lowered and the carbon fibers are easily impregnated, alcohols may be further added. The alcohols are not particularly limited, and examples thereof include methanol, ethanol, n-propyl alcohol and the like.
The ratio of alcohols to a total of 100 parts by mass of the matrix resin is preferably 1 to 8 parts by mass.

Additives such as a thickener, a curing agent, a polymerization initiator, a polymerization inhibitor, a pigment, an internal mold release agent, a flame retardant, a coupling agent, and a filler may be added to the matrix resin. As the additive, one type may be used alone, or two or more types may be used in combination.

Examples of the thickener include calcium hydroxide, magnesium oxide and the like. Examples of the curing agent include hexamethylenetetramine and the like. Examples of the internal mold release agent include stearic acid and zinc stearate. Examples of the flame retardant include aluminum hydroxide, antimony trioxide, antimony pentoxide and the like. Examples of the coupling agent include a silane coupling agent, a titanate coupling agent, an aluminate coupling agent, a zirconate coupling agent and the like.

The filler may be an inorganic filler or an organic filler. Examples of the inorganic filler include calcium carbonate, aluminum hydroxide, barium sulfate, clay, talc, silica, glass beads, alumina, mica, graphite, carbon black and the like. Examples of the organic filler include styrene resin and imide resin.

The method for producing SMC is not particularly limited. For example, using a known SMC manufacturing apparatus, a matrix resin paste is applied to carrier films (polyethylene film, polypropylene film, etc.) arranged one above the other so as to have a thickness of about 0.3 to 2.0 mm. do. A predetermined amount of carbon fibers cut to a predetermined length is sprayed on the paste applied on the lower carrier film, and carbon sprayed with the paste (resin composition) applied on the upper and lower carrier films. Insert the fiber. Then, the whole of them is passed between the impregnating rolls to impregnate the carbon fibers with the matrix resin, and the aging treatment is performed to obtain an SMC. The aging treatment is not particularly limited, and examples thereof include heat treatment at 40 to 70 ° C. for about 5 to 100 hours.

(Baking process)
The CFRP obtained in the molding step is fired to carbonize the matrix resin and, if necessary, the pitch contained therein to obtain a C / C composite material.
The firing is preferably carried out in an atmosphere of an inert gas. The inert gas is not particularly limited, and examples thereof include nitrogen gas.

The firing temperature is preferably 700 ° C. or higher and 2500 ° C. or lower, and more preferably 700 ° C. or higher and 1600 ° C. or lower. When the firing temperature is equal to or higher than the lower limit of the above range, carbonization of the matrix resin and pitch can be sufficiently promoted. When the firing temperature is not more than the upper limit of the above range, the progress of the graphitization reaction of the carbon fibers is small, and the physical properties of the obtained composite material can be easily controlled.

The C / C composite material obtained by firing is preferably densified. This makes it easier to obtain a SiC-C / C composite material with high thermal conductivity.
As a densification method, for example, a C / C composite material after firing is impregnated with a thermosetting resin such as a phenol resin or a thermoplastic resin such as tar or pitch, and then heated to carbonize. Examples thereof include a method or a CVD method in which a hydrocarbon gas such as methane or propane is thermally decomposed to obtain carbon. The C / C composite material after firing may be impregnated with a pitch in a plurality of times and carbonized.

The softening point of the pitch used for densifying the C / C composite material is preferably 70 ° C. or higher, more preferably 80 ° C. or higher. The softening point of the pitch is preferably 150 ° C. or lower, more preferably 90 ° C. or lower.

The toluene insoluble content of the pitch used for densifying the C / C composite material is preferably 10% or more, more preferably 13% or more. The toluene insoluble content of the pitch is preferably 30% or less, more preferably 20% or less. The pitch used for densification of the C / C composite material preferably contains substantially no quinoline insoluble matter. The pitch used for densifying the C / C composite material preferably contains 40% or more, preferably 50% or more of fixed carbon. The pitch used for densifying the C / C composite material is not limited to that described above.

The bulk density of the C / C composite material ^{is preferably 1.2 g / cm 3} or more, and more preferably 1.3 g / cm ³ or more. The bulk density of the C / C composite material is preferably 1.7 g / cm ³ or less, 1.6 g / cm ³ or less is more preferable. When the bulk density of the C / C composite is equal to or higher than the lower limit, the carbon matrix that reacts with the metallic Si is sufficient, and the presence of silicon carbide produced by the reaction is sufficient for the SiC-C / C composite. A reinforcing effect can be exhibited. When the bulk density of the C / C composite material is not more than the upper limit value, the metal Si is likely to be impregnated when the metal Si is melt-impregnated. Therefore, it is easy to suppress the occurrence of voids, cracks, and the like due to the region not impregnated with metallic Si.

The porosity of the C / C composite material is preferably 15% by volume or more, more preferably 20% by volume or more. The porosity of the C / C composite material is preferably 40% by volume or less, more preferably 35% by volume or less. When the porosity of the C / C composite material is not more than the above upper limit value, the carbon matrix is sufficient and the carbon matrix easily reacts with the metal Si. When the porosity of the C / C composite material is at least the above lower limit value, the impregnation of metallic Si is sufficient, and silicon carbide is easily sufficiently produced.

The carbon fiber content Vf per volume of the C / C composite material is preferably 20% by volume or more and 50% by volume or less. When the Vf of the C / C composite material is equal to or higher than the lower limit value, the strength of the SiC-C / C composite material is improved. When the Vf of the C / C composite material is not more than the above upper limit value, the carbon matrix easily reacts with the metallic Si and silicon carbide is easily produced.

(Melting impregnation process)
The C / C composite material is melt-impregnated with metallic Si, and the carbon in the C / C composite material is reacted with the metal Si to form silicon carbide to obtain a SiC-C / C composite material. The matrix in the resulting SiC-C / C composite consists of unreacted carbon and metallic Si and silicon carbide produced by the reaction.

Melt impregnation of metallic Si into the C / C composite material can be performed by various methods. For example, by holding the C / C composite material and the metal Si at a temperature of 1400 ° C. or higher and 2000 ° C. or lower under vacuum conditions, the metal Si is melt-impregnated inside the open pores of the C / C composite material, and a part thereof is melt-impregnated. Is reacted with carbon of the C / C composite material to obtain a SiC-C / C composite material.

The impurity content of metallic Si is preferably 1.5% by mass or less, more preferably 1.0% by mass or less, and even more preferably 0.5% by mass or less. When the impurity content of the metallic Si is not more than the upper limit value, it is possible to suppress impregnation inhibition and cracking of the composite material caused by impurities in the melt impregnation of the metallic Si.

As described above, in the method for producing a SiC-C / C composite material of the present invention, CFRP molded using SMC is adopted as an intermediate. Since SMC has excellent fluidity in the mold and can be easily formed into a desired shape, it does not require drilling of the C / C composite material after firing, and is compared with the conventional method using a non-woven fabric or the like. It has excellent productivity and can significantly reduce costs. Further, the carbon fibers normally used for SMC have a sufficient fiber length to exert a reinforcing effect, and the obtained SiC-C / C composite material has sufficient mechanical strength such as bending strength and compressive strength. Is expensive.

Further, the SiC-C / C composite material produced by using SMC is also excellent in thermal conductivity. In particular, it has excellent thermal conductivity in the pressurizing direction during molding. The reason why the thermal conductivity is improved by using SMC is not always clear, but it is presumed as follows.
For example, in the conventional method using a non-woven fabric, when pressure is applied during molding, almost all of the defibrated carbon fibers lie in a direction perpendicular to the pressure direction, so that C / C after firing is used. It is considered that the gap between the fibers in the composite material is small. Therefore, it is presumed that when the metal Si is melt-impregnated, it is difficult for the metal Si to be sufficiently impregnated between the fibers of the non-woven fabric in the pressure direction during molding. On the other hand, in molding using SMC, the ratio of carbon fibers remaining as bundles without being defibrated is usually high even after molding, and the ratio between carbon fibers in the C / C composite material is higher than that in the case of using non-woven fabric. It is thought that the gap will be large. As a result, it is presumed that when the metal Si is melt-impregnated, the metal Si is easily sufficiently impregnated in the pressurizing direction during molding, which is one of the factors for improving the thermal conductivity in the pressurizing direction during molding. Will be done. Further, since SMC easily flows during molding, it is considered that there are more carbon fibers whose fiber axial direction is directed in the pressurizing direction during molding or in a direction oblique to the pressurizing direction, as compared with the case of using a non-woven fabric. It is speculated that this can also contribute to the improvement of thermal conductivity in the pressurizing direction during molding.

[Carbon fiber reinforced silicon carbide composite material]
The SiC-C / C composite material of the present invention has a streak-like impregnated portion (matrix) containing either one or both of metallic Si and silicon carbide in a cross section cut in the pressurizing direction at the time of molding, and is streaky. The direction of the streaks in the impregnated part is random.

The SiC-C / C composite material of the present invention can be produced by the above-mentioned method for producing a SiC-C / C composite material of the present invention. By melt-impregnating the C / C composite material obtained by firing CFRP molded using SMC with metallic Si, the metallic Si is sufficiently impregnated in the pressurizing direction during molding, and the direction of the streaks in the impregnated portion is random. It is considered to be a SiC-C / C composite material.
The carbon fibers contained in the SiC-C / C composite material are preferably pitch-based carbon fibers from the viewpoint of excellent thermal conductivity.

The application of the SiC-C / C composite material of the present invention is not particularly limited, and for example, it can be used as a sliding material. Since the SiC-C / C composite material of the present invention has excellent thermal conductivity including the thickness direction (pressurization direction at the time of molding), brake discs and brakes used especially for wheels of two-wheeled vehicles, four-wheeled vehicles, aircraft, etc. Suitable for pads and the like.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to the following description.

[Example 1]
The mold is filled with SMC having ^{a FAW of 1000 g / m 2} containing pitch-based carbon fibers (filament diameter: 10 μm, number of filaments: 12,000, average fiber length: 25.4 mm) and phenol resin as a matrix resin. , 180 ° C. was pressure-molded to obtain a plate-shaped CFRP having a volume content Vf of carbon fibers per volume of 40% by volume.
The obtained CFRP was calcined at 750 ° C. for 5 hours in a nitrogen atmosphere to obtain a C / C composite material. The obtained C / C composite material and metallic Si were kept at 1600 ° C. under vacuum conditions, and the C / C composite material was melt-impregnated with metallic Si to obtain a SiC-C / C composite material. FIG. 1 shows an image of a cross section of the obtained SiC-C / C composite material cut in the thickness direction (pressurization direction at the time of molding).

[Comparative Example 1]
^{A sheet having a FAW of 170 g / m 2} containing a phenol resin as a matrix resin on a non-woven fabric is laminated in a mold and pressure-molded at 250 ° C., and the volume content Vf of carbon fibers per volume is 50% by volume. CFRP in the form of a plate was obtained. The obtained CFRP was calcined at 750 ° C. for 5 hours in a nitrogen atmosphere. Then, the impregnation carbonization process of impregnating the pitch and firing at 750 ° C. for 5 hours was performed twice. The obtained C / C composite material and metallic Si were kept at 1600 ° C. under vacuum conditions, and the C / C composite material was melt-impregnated with metallic Si to obtain a SiC-C / C composite material.

[Bending strength]
A plate-like body having a length L = 50.0 mm, a width W = 10.0 mm, and a thickness t = 2.0 mm was cut out from the composite material obtained in each example to obtain a bending test piece. The bending strength (MPa) in the thickness direction (pressurizing direction at the time of molding) was measured by applying a bending load to this test piece at a speed of 1 mm / min of the crosshead and determining the maximum load immediately before breaking.

[Compression strength]
For the composite materials obtained in each example, a rectangular parallelepiped compression test piece having a length L = 6.0 mm, a width W = 6.0 mm, and a thickness t = 10.0 mm was prepared. The compressive strength (MPa) of this test piece was measured in the thickness direction (pressurization direction at the time of molding) by applying a compressive load at a crosshead speed of 0.5 mm / min and determining the maximum load immediately before fracture.

[Thermal conductivity]
From the composite material obtained in each example, a plate-like body having a length L = 10.0 mm, a width W = 10.0 mm, and a thickness t = 2.0 mm was cut out and used as a test piece. The thermal conductivity (W / mK) of this test piece in the thickness direction (pressurization direction at the time of molding) at 27 ° C. was measured by a laser flash method.

The evaluation results of each example are shown in Table 1.

As shown in FIG. 1, the SiC-C / C composite material of Example 1 produced by using SMC has either one or both of metallic Si and silicon carbide in a cross section cut in the pressurizing direction at the time of molding. The direction of the streaks in the impregnated part of the streaks including the streaks was random.
As shown in Table 1, the SiC-C / C composite material of Example 1 produced by using SMC has sufficiently high bending strength and compressive strength, and the SiC-C / C of Comparative Example 1 using a non-woven fabric is used. Compared to composite materials, it was superior in thermal conductivity in the thickness direction (pressurization direction during molding).

Claims (12)

A carbon fiber reinforced plastic is molded using a sheet molding compound containing carbon fiber and a matrix resin, and the carbon fiber reinforced plastic is fired to obtain a carbon fiber reinforced carbon composite material, and metallic Si is added to the carbon fiber reinforced carbon composite material. A method for producing a carbon fiber reinforced silicon carbide-based composite material that is melt-impregnated. The method for producing a carbon fiber-reinforced silicon carbide-based composite material according to claim 1, wherein the carbon fibers are pitch-based carbon fibers. The method for producing a carbon fiber-reinforced silicon carbide-based composite material according to claim 1 or 2, wherein the carbon fiber has a fiber length of 10 mm or more and 60 mm or less. The method for producing a carbon fiber-reinforced silicon carbide-based composite material according to any one of claims 1 to 3, wherein the matrix resin is a phenol resin. The method for producing a carbon fiber-reinforced silicon carbide-based composite material according to any one of claims 1 to 4, wherein the FAW of the sheet molding compound is 200 g / m ² or more and 2000 g / m ^{2 or less.} The method for producing a carbon fiber-reinforced silicon carbide-based composite material according to any one of claims 1 to 5, wherein the carbon fiber content per volume of the carbon fiber reinforced plastic is 20% by volume or more and 60% by volume or less. The method for producing a carbon fiber-reinforced silicon carbide-based composite material according to any one of claims 1 to 6, wherein molding using the sheet molding compound is performed by a hot press method. The method for producing a carbon fiber-reinforced silicon carbide-based composite material according to any one of claims 1 to 7, wherein the carbon fiber reinforced plastic is fired in an inert gas atmosphere. The method for producing a carbon fiber-reinforced silicon carbide-based composite material according to any one of claims 1 to 8, wherein the impurity content of the metallic Si is 1.5% by mass or less. The method for producing a carbon fiber-reinforced silicon carbide-based composite material according to any one of claims 1 to 9, wherein the carbon fiber-reinforced carbon composite material is melt-impregnated with metallic Si at 1400 ° C. or higher and 2000 ° C. or lower under vacuum conditions. .. Carbon having a streak-like impregnated portion containing either one or both of metallic Si and silicon carbide in a cross section cut in the pressurizing direction at the time of molding, and the streak direction of the streak-like impregnated portion is random. Fiber-reinforced silicon carbide-based composite material. The carbon fiber-reinforced silicon carbide-based composite material according to claim 11, wherein the contained carbon fiber is a pitch-based carbon fiber.

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