JPS5969408A - Manufacture of composite carbon-carbon material - Google Patents

Abstract

PURPOSE:To manufacture the titled material without cracking each layer between fabrics of carbon fiber by laminating fabrics of carbon fiber or fiber as a starting material for carbon fiber and prepreg impregnated with thermosetting resin and by stitching up the laminate with stitching thread of said fiber before heating under pressure.. CONSTITUTION:Fabrics 10 woven from weft 10a of carbon fiber and warp 10b of carbon fiber and prepreg impregnated with thermosetting resin 11a as a starting material for a carbonaceous material are laminated in a prescribed shape. The laminate is stitched up with stitching thread 12 of carbon fiber, and it is heated under pressure to form a curved preform. After finishing the preforming stage, the preform is repeatedly subjected to carbonization, graphitization and pitch impregnation so as to provide prescribed specific gravity. Thus, a composite carbon-carbon material is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a carbonaceous material reinforced with carbon fibers, that is, a carbon-carbon composite material.

Carbon/carbon composite materials are lightweight (specific gravity around 1.5 to 1.6)
It has extremely excellent heat resistance (approximately 2,500 to 3,000'0) and has high strength at high temperatures, making it an extremely suitable material for use in parts exposed to high heat, such as the nozzle part of a flying object. It is useful.

Conventionally, this carbon-carbon composite material has been manufactured through a process as shown in FIG.

First, in the Briform process 1, a prepreg made by impregnating a carbon fiber woven fabric 10 with a thermosetting resin 11 such as a phenolic resin is prepared according to the shape of the product, such as a plate shape as shown in FIG. Laminate the layers to form a cylindrical shape as shown in Figure 3, and press the laminate at 100 to 240 degrees.
C. to form a hardened molded product. Next, in the carbonization treatment step 2, the cured molded product described above is gradually heated in the range of 450 to 900 ° C to perform carbonization treatment, and in the graphitization treatment step 3, the cured molded product is heated in the range of 2000 to 2900 °C. Graphitization treatment is performed by gradual heating. Gas is generated by thermal decomposition of the thermosetting resin 11 in this carbonization treatment and graphitization treatment, and the loosely formed molded body is impregnated with a pitch material in a pitch impregnation step 4, and then further carbonized in a carbonization treatment step 5. In graphitization treatment step 6, carbonization and graphitization are performed again. Then, pitch impregnation, carbonization, and graphitization are repeated until the specific gravity of the compact reaches a predetermined value (approximately 1.5 to 1.6), and when the specific gravity reaches the predetermined specific gravity, it becomes a carbon-carbon composite material. The molded body is completed.

The prepreg woven fabric 10 used in the Briform process 1 is not limited to carbon fiber, but may also be a woven fabric made of carbon fiber raw material A fiber, for example polynitroacrylic (PAN) fiber, rayon fiber, etc. . This is because carbonization and graphitization treatments are performed during the manufacturing process of carbon-carbon composite materials, so polynitroacrylic fibers, rayon fibers, etc. are also carbonized and graphitized, changing their composition to almost the same as carbon fibers. Because it does. However, in terms of strength, it is better to use a woven carbon fiber fabric in which carbon crystals are aligned in the same direction.

By the way, in such a conventional manufacturing method, a prepreg laminate in which a carbon fiber woven fabric 10 is impregnated with a thermosetting resin 11 is heated from a relatively low temperature of about 100 to 240°C to a temperature of 2000 to 200°C. During the firing process, the temperature is gradually lowered until it reaches a high temperature of 2900°C, the thermosetting resin 11 thermally decomposes, gas is generated, bubbles are formed inside the molded body, and carbon fibers are Due to the difference in thermal expansion coefficients between the
Since carbon fiber has a higher thermal conductivity than thermosetting resin 11 and carbon fiber, heat conduction in the thickness direction of the molded body is worse than heat conduction within the lamination plane of carbon fiber Kaki '4J10. Therefore, the temperature distribution within the molded body becomes non-uniform, and the thermal stress distribution within the molded body also becomes non-uniform. In the carbonization process 2, in which the composition within the molded article changes rapidly due to the complex effects of these factors, cracks (delamination) between the layers of the carbon fiber woven fabric 10 occur, causing damage to the molded article. If the wall thickness is thick or the shape is complicated, product defects due to the occurrence of cracks will increase, and the manufacturing yield of molded bodies made of carbon/carbon composite material will be extremely poor.

The present invention has been made in view of the above, and its purpose is to prevent cracks that occur between layers of carbon fiber woven fabric in the manufacturing process of carbon fiber-reinforced carbonaceous materials, that is, carbon-carbon composite materials. Therefore, the gist of the present invention is to add a prepreg laminate in which carbon fiber or a woven fabric made of carbon fiber raw material fiber is impregnated with a thermosetting resin of carbon material raw material. Before heating the prepreg laminate under pressure to form a hardened molded body by heating under pressure, the laminate was sewn together using a surplus of carbon fibers or raw material fibers of carbon fibers. That's true.

The present invention will be described below based on embodiments shown in the accompanying drawings.

Figure 4 shows 11t! of the present invention! ! FIG. 2 is an explanatory diagram showing an example of a prepreg laminate in the manufacturing method.

In No. 41A, 10 is a weft 10a made of carbon fiber,
It is a woven fabric woven with warp yarns 10b. First, for this woven fabric, we will use resol type phenolic resin, which is a thermosetting resin, for ￥1
Prepreg impregnated with No. 13 is laminated to form a predetermined shape,
This laminate is sewn together with a surplus 12 of polynitroacrylic (PAN) flame-retardant fibers, ie carbon fibers. Next, the prepreg laminate sewn together using the surplus 12 is sewn together with 100 ml of laminate while applying pressure in the same manner as before.
The briform step 1 is completed by heating at a temperature of ~240°C to form a hardened molded product.

The hardened molded body produced in Buri 7 Ohm E step 1 is then subjected to repeated carbonization, graphitization, and pitch impregnation treatments in the same way as the conventional treatment steps shown in FIG. Once the specific gravity has been reached, a molded body made of carbon/carbon composite phase is completed.

As mentioned above, when the prepreg laminate is sewn together using the surplus 12 in the buriform process 1, the resol-based phenolic resin 11a is thermally decomposed and gas is generated due to heating in the buri7ohme culm 1, carbonization process 2, etc. Even if the molded body is fired, the gas easily escapes to the outside of the molded body along the shortest path in the thickness direction along the surplus 12, making it difficult for air bubbles to remain inside the molded body after firing. In addition, the laminated layers, which are weak in strength and have not been reinforced with carbon fibers, are mechanically reinforced by the surplus 12.Furthermore, since the surplus 12 is arranged in the thickness direction, heat is applied during the firing process. Since it becomes easier to escape in the plate thickness direction along the surplus 12, the non-uniformity of temperature distribution that conventionally occurred in the molded body is alleviated.

For these 11 reasons, it is possible to prevent cracks (delamination) that have conventionally occurred between the M's that have not been reinforced with carbon fibers.

In this example, the remainder 12 is polynitroacrylic (pA
h+) flame-resistant fiber, that is, carbon fiber, was used,
Without being limited thereto, polynitroacrylic fibers, rayon fibers, etc., which are carbon fiber material fibers, may be used as they are. This is similar to the fact that a woven fabric such as nitroacrylic fiber can be used instead of the woven fabric 10 of carbon fiber, and polynitroacrylic fiber can be This is because the fibers are also carbonized. However, in this case as well, the use of the carbon fiber remainder 12 provides superior strength.

Next, Table 1 shows the occurrence of cracks (delamination) in the carbon-carbon composite specimen manufactured by the manufacturing method of the present invention in comparison with the specimen manufactured by the conventional manufacturing method. . In addition, cracks can be confirmed not only by visually inspecting them, but also by applying alcohol to the surface of the composite material and observing its evaporation.If there are areas where evaporation is delayed, this means that alcohol has entered the cracks in those areas. Crack
-1 It was determined that a failure had occurred.

/ 7-''/' / Recording "7-ohm culm heating of the prepreg laminate (before heating at the bottom, the prepreg laminate is sewn together using carbon fibers or carbon fiber raw material fibers) As a result, it is possible to prevent cracks that occur between carbon fiber layers during the manufacturing process of carbon-carbon composite materials.
Even if the shape of the carbon/carbon composite material to be molded becomes larger or more complex, by adjusting the distribution of the number of surplus fibers, it is possible to minimize the occurrence of defective products in the molded product of carbon/carbon composite H and improve the manufacturing process. This has the effect of improving retention.

In addition, the shear strength of the laminated surface of the carbon/carbon composite material molded body,
Furthermore, since the thermal shock resistance in the direction of the laminated plane is significantly improved, an additional effect of significantly improving the structural strength of products formed from the carbon/carbon composite material, such as rocket motor nozzles, etc., can also be obtained.

[Brief explanation of the drawings] Fig. 1 is a block diagram showing the manufacturing process of carbon-carbon composite material, Fig. 2 is an explanatory drawing showing an example of a prepreg laminate in the conventional manufacturing method, and Fig. 3 is a block diagram showing the manufacturing process of carbon-carbon composite material. FIG. 4 is an explanatory diagram showing another example of the prepreg laminate in the manufacturing method. FIG. 4 is an explanatory diagram showing an example of the prepreg laminate in the present invention. 1... Preform process 2, 5... Carbonization process 3.6... Graphitization process 10... Woven fabric 10a...
・Weft thread 10b... Warp thread 11... Thermosetting resin 11a... Luzol-based phenolic resin 1
2...Residual patent applicant Nissan Motor Co., Ltd.: 2)

Claims (1)

[Claims] A briform process in which a laminate of prepreg, which is made by impregnating a woven fabric made of carbon fiber or carbon fiber as a raw material fiber with a thermosetting resin as a carbon material raw material, is heated under pressure to form a hardened molded product, followed by carbonization. In a method for producing a carbon-carbon composite material having a treatment step, a graphitization step, and a pitch impregnation step, carbon fiber or carbon fiber A method for producing a carbon-carbon composite material, characterized in that the laminate is sewn together using a surplus of raw material fibers.