JPH03193665A - Production of carbon fiber reinforced carbon composite material - Google Patents

Abstract

PURPOSE:To obtain a carbon fiber reinforced carbon composite material having high strength and useful as an aeronautical or space material by weaving opened unidirectional prepreg of a specified thickness into cloth form, laminating, molding and burning the resulting cloth. CONSTITUTION:Opened unidirectional prepreg 1 consisting of carbon fibers and starting material for a carbon matrix such as phenol resin and having <=100mum thickness (d) of the thickness part is produced and woven into cloth form. The resulting cloth is laminated, molded, impregnated and carbonized or further graphitized to obtain a carbon fiber reinforced carbon composite material.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a high-strength carbon fiber-reinforced carbon composite material in which fabrics are laminated.

The carbon fiber reinforced carbon composite material of the present invention has high strength,
It is particularly suitable as an aviation and space material.

(Prior Art) Carbon fiber-reinforced carbon composite materials (hereinafter referred to as C/C composites), which have high specific strength and excellent heat resistance, occupy an important position as materials for aviation, space, etc.

Conventionally, three methods are known as methods for manufacturing C/C composites.

The first is polyacrylonitrile (PAN)-based, pitch-based, or rayon-based carbon fiber short fibers, long fibers, or fabrics, and carbon matrix raw materials such as thermosetting resins such as phenol resins and furan resins, or pitches. This is a method in which the mixture is heated and molded, then carbonized in an inert gas atmosphere, and if necessary, the cycle of impregnation with resin, pitch, etc., and carbonization is repeated (for example, Japanese Patent Application Laid-Open No. 62-212262). . In particular, when pitches are used as a carbon matrix raw material, the molded body is fixed with a fixing material such as metal or ceramics to suppress blistering and carbonized, and then impregnated, carbonized, and graphitized using conventional methods. A method of obtaining a C/C composite by processing has also been developed (for example, Japanese Patent Application Laid-Open No. 62-241871).
Publication No.).

The second method is to obtain a C/C composite by forming carbon fibers into a general shape in advance, and then depositing carbon in the gaps between the carbon fibers using a chemical vapor deposition method (for example, Ca
rbon Vol, 6. p397-403.196
8 years).

The third method is a combination of the first method and the second method. That is, impregnation with resin, pitch, etc. in the 's1 method,
The second method, chemical vapor deposition, is used instead of the carbonization cycle.

(Problems to be Solved by the Invention) However, in the conventional C/C composite made by laminating fabrics, (1) the carbon fiber bundles constituting the fabrics are thick, so the carbon matrix raw material is unevenly dispersed inside the fiber bundles; ■When filler is added to the carbon matrix raw material, the filler is captured by the fibers due to the small diameter of the carbon fibers, making it difficult to disperse the filler uniformly. ■Because the carbon fiber bundles that make up the fabric are thick, Large irregularities occur on the surface of the fabric, and these irregularities cause large pores to form in the carbon matrix, making it difficult to obtain sufficient strength and physical properties. Therefore, an object of the present invention is to provide a method for manufacturing a high-strength C/C composite made of laminated fabrics.

(Means for Solving the Problem) In order to solve the problem, the present invention uses a fabric-like prepreg that is woven from opened unidirectional prepreg made of carbon fibers and carbon matrix raw materials. It was discovered that a high-strength C/C composite can be obtained by this method, leading to the present invention.

That is, the present invention has a thickness of 100 pm at the thickest part, which is composed of carbon fiber bundles and carbon matrix raw materials.
Create the following opened unidirectional prepreg,
The method for producing a C/C composite is characterized in that the unidirectional prepreg is then woven into a fabric-like prepreg, and then the fabric-like prepreg is laminated, molded, and fired.

FIG. 2 is an example of a fabric-like prepreg obtained from a unidirectional prepreg that has been opened and used in the explanation of the present invention. 1 in Fig. 2 is what is referred to as a "spread unidirectional prepreg" in the present invention. Spread unidirectional prepreg is usually thickest in the center and as it goes toward the ends. It's getting thinner. The "thickness of the thickest part" used in the explanation of the present invention is the thickness of the prepreg before it is made into a fabric, and even if it is woven, the thickness will hardly change. Therefore, the thickness is not substantially different from the thickness of the central part of the opened unidirectional prepreg shown as d in FIG.

Hereinafter, the content of the present invention will be explained in detail.

The carbon fibers used in the present invention include PAN type, pitch type,
Known carbon fibers such as rayon-based and phenol-based carbon fibers can be used. The carbon fibers may be in the form of continuous fibers or yarns.

As the carbon matrix raw material, thermosetting resins such as phenol resins, thermoplastic resins such as vinyl chloride, or petroleum-based or coal-based pitches are used. Furthermore, in order to improve the carbonization yield of the carbon matrix, an inorganic substance such as silicon carbide, carbon black, or graphite may be added as a filler if necessary.

Composed of carbon fiber bundles and carbon matrix raw materials,
In order to create a spread unidirectional prepreg having a thickness of 100 pm or less at its thickest portion, the following methods can be exemplified, and any of these methods may be used.

In other words, (1) the carbon fiber bundle is opened by rolling, ultrasonic waves, air flow, etc., and then the carbon matrix raw material is impregnated into the carbon fibers by means such as dipping, coating, spraying, etc.; (2) the carbon matrix is injected into the carbon fiber bundle; (2) Impregnating the carbon fiber bundle with the carbon matrix raw material and opening it at the same time, etc.

At this time, it is important that the thickness of the thickest part of the opened unidirectional prepreg is 100 pm or less. When the thickness of the thickest part of the unidirectional prepreg exceeds 100 pm, ■ the dispersion of the carbon matrix raw material inside the carbon fiber bundles that make up the unidirectional prepreg becomes uneven; When made into a fabric-like prepreg, the unidirectional prepreg that makes up the fabric-like prepreg is thick, so large unevenness occurs on the surface of the fabric-like prepreg, and these unevenness and protrusions cause large pores in the carbon matrix. It is not desirable for the following reasons.

As for the thickness of the opened unidirectional prepreg, the thinner it is, the more effective it is, so even if it is a single layer of carbon fiber, the effect can be sufficiently exhibited. That is, the lower limit of the thickness of the unidirectional prepreg depends on the diameter of the carbon fiber used, but since carbon fiber is usually about 5 to 7 pm even if it is thin, this is approximately the lower limit.

Next, the surfaces of the unidirectional prepregs are semi-cured by heating or volatilization of the solvent to a touchable state, and then woven into a cloth to obtain a fabric-like prepreg. The form of the fabric may be any form such as plain weave or satin weave.

Since the prepreg of the present invention is thin and flexible, it can be easily made into a fabric shape.

After laminating the fabric prepreg obtained in this way,
Molding is performed to obtain a molded body. During molding, heating may be performed if necessary.The molded body is then subjected to carbonization treatment as described above, and then impregnation treatment, carbonization treatment, and graphitization treatment are performed by conventional methods to form a high-strength C/C. You can get a composite.

(Function) Composed of carbon fiber bundles and carbon matrix raw materials,
An opened unidirectional prepreg having a thickness of 100 pm or less at the thickest part is created, and then the unidirectional prepreg is woven into a fabric-like prepreg, and then the fabric-like prepreg is laminated and heated. By firing, the thickness of the carbonaceous matrix layer formed between the carbon fiber bundles becomes smaller, thereby making it possible to create a C/C composite with small pores and high strength.

(Example) Example I PAN-based carbon fiber fiber diameter approximately 7 pm, 12000
filament) and phenolic resin (manufactured by Asahi Yokuzai Kogyo, R
After being impregnated with M 3000A), the fibers were spread by being rolled down using a roll to create a spread unidirectional prepreg made of a carbon fiber bundle and a phenol resin having a thickness of 72 pm at the thickest part. Then, the prepreg was woven into a plain-woven fabric prepreg.

The fabric-like prepregs described above were laminated in a 12 cm square mold and press-molded at 150°C and 100 kgf/cm' to form a molded product (120 mm x 120 mm x 10 m).
m) was obtained. This molded product was heated at a heating rate of 10°C/hour.
It was heated to 000°C to form a carbide. Next, the process of impregnating this carbide with pitch for impregnation and carbonizing it was repeated four times to obtain a C/C composite (bulk density: 1.58 g/cm'). The pore distribution of the obtained C/C composite is
As shown in the figure. In FIG. 1, the horizontal axis represents the diameter of the pores, and the vertical axis represents the pore volume. This C/C composite has lO~100pm
A relatively small amount of large pores is present.

Further, Table 1 shows the values of the bending strength and tensile strength of the obtained C/C composite.

Comparative Example 1 Commercially available PAN-based carbon fiber fabric fiber diameter 7μI, 3000
Filament, basis weight 400 g 7 m 2.8 sheets satin weave) and phenol resin (manufactured by Asahi Yokuzai Kogyo, RM 3000
A) was impregnated to create a fabric-like prepreg. In addition,
In an 8-ply satin weave fabric, the thickest part is at the point where the warp and weft intertwine. Since the thickness of the fabric at the intertwining point was 300 pm, half of that was taken as the thickness of the unidirectional prepreg. Therefore, the thickness of the thickest part of the unidirectional prepreg in Comparative Example 1 was 150 Pm.

Using the fabric prepreg, a C/C composite (bulk density 1.60 g/am") was obtained in the same manner as in Example 1. The pore distribution of the obtained C/C composite is shown in Figure 1. Compared to Example 1, there are a large number of large pores with lθ~100 pm.

Table 1 also shows the values of the bending strength and tensile strength of the C/C composites obtained.

*The thickness of the thickest part of the fabric prepreg using 8-ply satin weave fabric was 300 pm, so half of that was taken as the thickness of the unidirectional prepreg.

As seen in FIG. 1 and Table 1, the C/C composite obtained by the present invention has a reduced pore size of about 10 to 100 pta by using opened unidirectional prepreg. It can be seen that both bending strength and tensile strength are improved.

(Effects of the Invention) As described above, according to the present invention, a fabric-like prepreg obtained by weaving opened unidirectional prepreg is laminated,
A high-strength C/C composite can be obtained by hot forming and firing.

[Brief explanation of drawings]

Figure 1 is a diagram showing the pore distribution of the C/C composite obtained in Example 1 and Comparative Example 1 of the present invention, and Figure 2 is a diagram showing the pore distribution of the C/C composite obtained in Example 1 of the present invention and Comparative Example 1. It is a schematic diagram of the cut surface of the obtained fabric-like prepreg. 1: Spread unidirectional prepreg d: Thickness of the thickest part at the center of the spread unidirectional prepreg and 4 others [: Spread unidirectional prepreg d: Spread unidirectional prepreg Thickness of the thickest part in the center of the blib leg

Claims (1)

[Claims] 1. Create a spread unidirectional prepreg that is composed of carbon fiber bundles and carbon matrix raw materials and has a thickness of 100 pm or less at the thickest part, and then weave the unidirectional prepreg to form a fabric-like material. A method for producing a carbon fiber-reinforced carbon composite material, which comprises preparing a prepreg, then laminating, molding, and firing the fabric-like prepreg.