Interface features of the C/C composite during its forming process with a coal-tar-pitch as the precursor of the carbon matrix

The forming of the C/C composite usually includes many repetitive processes of impregnating, carbonization and heat-treatment at high temperatures when the coal-tar-pitch is used as the precursor of the carbon matrix. For the validity of densification, the impregnating process is applied at high pressures and at high temperatures. In this work, the interface features of the C/C composite during its forming process were studied systematically. It has been found that the interface feature of the fiber/matrix in the fiber bundles formed in the initial stage and the fiber/matrix interfaces between the fiber bundles formed throughout the forming process of the C/C composite. With the increase of the density of the C/C composite, the interface strength (IS) tended to increase. The IS of the fiber/matrix in the fiber bundles is much higher than that between the fiber bundles. The temperature of the heat-treatment (HTT) is a key factor to influence the interface strength. Higher HTT will decrease the interface strength due to the forming of the micro-cracks at the interfaces. The interface features could be controlled by the HTT.