JPH04317465A - Carbon fiber reinforced carbon composite material - Google Patents

Abstract

PURPOSE:To suppress the waving of yarn composed of carbon fibers and to enhance the strength of a composite material by regulating the quotient of the thickness of carbon fiber fabrics in the laminating direction by the number of the fabrics laminated to a specified value or below. CONSTITUTION:Fabrics produced with yarn composed of many carbon fibers are coated with a binder (such as resol type phenol resin), laminated and subjected to hot press molding. The resulting molded body is fired in an atmosphere of gaseous nitrogen, made dense and graphitized to produce a carbon fiber reinforced carbon composite material. At this time, the quotient of the calculated thickness of the carbon fiber fabrics used, that is, the weight per unit area by the bulk density of the fabrics is reduced and the quotient of the thickness of the carbon fiber fabrics in the composite material in the laminating direction by the number of the fabrics laminated is regulated to <=0.14mm by reducing the thickness of the fabrics by compression.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to carbon fiber reinforced carbon composite materials.

0002

[Prior art] Carbon fiber reinforced carbon composite material (hereinafter referred to as C/C
(referred to as composite materials) are lightweight, have excellent mechanical properties,
Has heat resistance. Therefore, it is extremely useful as aerospace materials such as disc brakes and rocket nozzles, as well as various parts used under high temperatures. The general manufacturing method for C/C composite materials is to impregnate or coat carbon fiber thread, tow, woven fabric, non-woven fabric, etc. with a binder such as thermosetting resin, tar, pitch, etc., and then laminate and mold the materials. , firing, and then impregnation with a binder and firing are repeated. In order to make the C/C composite material manufactured in this manner high in strength, the carbon fibers must be long fibers, and a method using woven fabric is generally used.

0003

[Problem to be solved by the invention] When using woven fabric,
Because the warp and weft threads of the woven fabric pass through each other at the intersection, the threads undulate in the thickness direction of the woven fabric. For this reason, when a load is applied to the C/C composite material, stress is generated not only in the length direction of the fibers but also in a direction perpendicular to this, making the fibers more likely to break. In other words, due to the waviness of the yarn, the strength of the C/C composite is lower than when stress is applied only in the longitudinal direction of the fibers.

[0004] An object of the present invention is to provide a high-strength C/C composite material whose strength decreases little due to waviness.

[0005]

[Means for Solving the Problems] As a result of repeated research on the relationship between the waviness of the threads described above and the strength of C/C composite materials, the present inventors have found that carbon fiber woven fabric 1 in C/C composite materials It has been found that by reducing the thickness per sheet, that is, the value obtained by dividing the thickness of the woven fabric in the laminating direction by the number of laminated woven fabrics, the waviness of the yarn can be reduced and high strength can be achieved.

The present invention relates to a C/C composite material in which the thickness of the carbon fiber woven fabric in the stacking direction divided by the number of layers of the woven fabric is 0.14 mm or less.

[0007] In order to reduce the thickness of each carbon fiber woven fabric, the calculated thickness of the carbon fiber woven fabric used, that is, the value obtained by dividing the basis weight, which is the weight per unit area, by the bulk density of the fiber. It is necessary to reduce the number of layers and increase the number of laminated sheets. The calculated thickness of the woven fabric that is preferable for high strength is 0.10 mm.
It is as follows. Furthermore, increasing the fiber volume fraction of the C/C composite material is effective in increasing the strength because it is possible to compress the woven fabric and reduce the thickness, and also to increase the fiber reinforcing effect. However, if the fiber volume fraction becomes too large, it becomes difficult to impregnate the binder described later, so the preferred fiber volume fraction for high strength is 40 to 70%. By combining the above two methods of using a woven fabric with a small calculated thickness and increasing the fiber volume fraction, C/
The thickness per woven fabric in the C composite material can be reduced, and as a result, the waviness of the threads is reduced and high strength can be achieved. The value obtained by dividing the thickness of each woven fabric in the C/C composite material required for high strength, that is, the thickness in the lamination direction of the woven fabric by the number of laminated woven fabrics, is 0.14 mm or less. Furthermore, in order to reduce yarn waviness and significantly improve strength, it is preferable that the thickness of each woven fabric be 0.10 mm or less.

In the present invention, the origin of carbon fiber is PAN
It may be any type, pitch type, rayon type, etc. Further, the weaving method of the woven fabric may be any of plain weave, satin weave, twill weave, etc. A C/C composite material is produced by impregnating or coating this woven fabric with a binder, shaping it, firing, and then repeating impregnation with a binder and firing.

[0009] The binding material may be a thermosetting resin, a thermoplastic resin,
Any material commonly used as a raw material for carbon materials such as tar or pitch may be used. These binding materials are applied to a woven fabric and then hot-press molded. Alternatively, it is formed by a known method such as impregnating a woven fabric fixed with a jig with a binding material. This molded body is carbonized and fired in a non-oxidizing atmosphere at a temperature of 600° C. or higher, preferably 900° C. or higher to obtain a C/C composite material. In order to densify the obtained C/C composite material, impregnation with a binder and firing are performed as appropriate, and if necessary, a
Graphitization treatment is carried out at ℃. In addition to the above method, there is also a method in which a layered woven fabric is filled with pyrolytic carbon by CVD to produce a C/C composite material, and a method in which this method is repeated with impregnation of a binder and firing. You can also combine them.

0010

[Example] Next, an example of the present invention will be described.

Example 1 PAN carbon fiber (tensile strength 3.5 GPa, tensile modulus 230 GPa, tensile elongation at break 1.5%, single fiber diameter 7 μm)
A plain woven fabric (calculated thickness 0.09 mm) with a basis weight of 150 g/m2 using 2,000 threads with a bulk density of 1.75 g/cm3) was coated with resol type phenolic resin (
Hitachi Chemical Co., Ltd., VP-11N) was coated, and this
The sheets were laminated and hot-press molded to obtain a molded body. This molded body was fired in a nitrogen gas atmosphere at a temperature increase rate of 10°C per hour to 1000°C to obtain a C/C composite material. Furthermore, after repeating the above phenol resin impregnation and firing three times for densification, 28
A C/C composite material having a thickness of 3 mm, a thickness of 0.13 mm per woven fabric, a bulk density of 1.69 g/cm3, and a fiber volume fraction of 63% was obtained by graphitizing at 00°C. Table 1 shows the strength of the obtained C/C composite material.

Example 2 A plain woven fabric with a basis weight of 120 g/m2 (calculated thickness of 0.5 g/m2) using the same 1000 carbon fiber threads as in Example 1.
07 mm) was coated with the same phenolic resin as in Example 1, and 28 sheets of this were laminated and hot-press molded to obtain a molded body. The obtained molded body was fired, densified, and graphitized in the same manner as in Example 1 to give a thickness of 3 mm and a thickness of 0.11 mm per woven fabric.
, bulk density 1.68 g/cm3, fiber volume fraction 64% C
/C composite material was obtained. Table 1 shows the strength of the obtained C/C composite material.
Shown below.

Comparative Example 1 A plain woven fabric with a basis weight of 200 g/m2 (calculated thickness of 0.5 g/m2) using the same 3000 carbon fiber threads as in Example 1.
11mm) with the same resin as in Example 1, and
Seven sheets were laminated and hot-press molded to obtain a molded body. The obtained molded body was fired, densified, and graphitized in the same manner as in Example 1 to obtain a thickness of 3 mm, a thickness of 0.17 mm per woven fabric, a bulk density of 1.70 g/cm3, and a fiber volume fraction. A 64% C/C composite was obtained. Table 1 shows the strength of the obtained C/C composite material.

Comparative Example 2 A plain woven fabric with a basis weight of 310 g/m2 (calculated thickness of 0.5 g/m2) using the same 6000 carbon fiber threads as in Example 1.
18mm) was coated with the same resin as in Example 1, and this
One sheet was laminated and hot-press molded to obtain a molded body. The obtained molded body was fired, densified, and graphitized in the same manner as in Example 1 to obtain a thickness of 3 mm, a thickness of 0.27 mm per woven fabric, a bulk density of 1.69 g/cm3, and a fiber volume fraction. A 64% C/C composite was obtained. Table 1 shows the strength of the obtained C/C composite material.

Example 3 Pitch-based carbon fiber (tensile strength 2.7 GPa, tensile modulus 490 GPa, tensile elongation at break 0.6%, single fiber diameter 10
A plain weave fabric (calculated thickness 0.08 mm) with a basis weight of 170 g/m2 using 1000 threads with a bulk density of 2.16 g/cm3, , VP801), and this
0 sheets were laminated and hot-press molding was performed to obtain a molded body. The obtained molded body was heated at a heating rate of 10°C per hour in a nitrogen gas atmosphere for 10 minutes.
It was fired to 00°C to obtain a C/C composite material. Further, for densification, coal pitch having a softening point of 90° C. and a fixed carbon content of 55% by weight was vacuum impregnated at 200° C., and firing was performed under the above firing conditions. After this, pitch impregnation and firing were repeated three times, and graphitized at 2800°C to obtain a woven fabric with a thickness of 4 mm.
Thickness per sheet: 0.13mm, bulk density: 1.85g/cm
3. A C/C composite material with a fiber volume fraction of 60% was obtained. Table 2 shows the strength of the obtained C/C composite material.

Comparative Example 3 A plain woven fabric with a basis weight of 250 g/m2 (calculated thickness of 0.1
2mm) was coated with the same resin as in Example 3, and this was
The sheets were laminated and hot-press molded to obtain a molded body. This molded body was fired, densified, and graphitized in the same manner as in Example 3, and the thickness was 4 mm, the thickness per woven fabric was 0.19 mm, the bulk density was 1.86 g/cm3, and the fiber volume fraction was 60. % C/C composite material was obtained. Table 2 shows the strength of the obtained C/C composite material.

[0017]

[Table 1]

[0018]

[Table 2]

Tables 1 and 2 show that the C/C composite materials of the Examples are superior to those of the Comparative Examples in both bending strength and tensile strength.

[0020]

Effects of the Invention The C/C composite material of the present invention has high strength because the thickness of each woven fabric is set to 0.14 mm or less to reduce yarn waviness.

Claims (1)

[Claims] 1. A carbon fiber-reinforced carbon composite material in which the thickness of the carbon fiber woven fabric in the stacking direction divided by the number of layers of the woven fabric is 0.14 mm or less.