PORE STRUCTURE OF CARBON-CARBON COMPOSITES STUDIED BY SMALL-ANGLE X-RAY-SCATTERING

The development of voids in the fibers and in the matrix of a carbon/c arbon composite due to different temperature treatments (1800-degrees- C, 2100-degrees-C, and 2400-degrees-C) was studied by small-angle X-ra y scattering (SAXS). Both the scattering of the composite and the fibe rs were measured, the respective part of the matrix was obtained by su btracting the scattering signal of the fiber from that of the composit e. It was observed that the fibers are only slightly influenced by the heat treatment, showing a small increase of the pore size and a weakl y more preferred orientation in fiber length direction. The matrix, ho wever, exhibits a pronounced increase of pore size. In particular, lar ge pores develop in the material as a consequence of the stress-induce d graphitization of the matrix.