Carbon/carbon(C/C)–Zr–Ti–C composites were fabricated using chemical vapor infiltration and liquid metal infiltration processes. The residual thermal stress (RTS) distribution in the C/C–Zr–Ti–C composites was analyzed by Raman spectroscopy and finite element (FE) calculation. The mechanical behaviors of C/C–Zr–Ti–C composites with three types of carbon fiber preforms were tested. The results showed that there was very high compressive RTS in the fibers and high tensile RTS in the pyrocarbon (PyC) in the marginal region near the carbide. However, in the central region away from the carbide, relatively low compressive stress and tensile RTS were found in the fibers and PyC, respectively. The FE analysis showed that the introduction of carbide into the C/C composites caused a significant increase of the RTS in the PyC near the carbide, indicating that the carbide could change the RTS distribution in C/C composites. Moreover, the distribution of the RTS and its release combined with the carbide distribution and fiber architecture led to variations in the mechanical performance of composites with different preforms.

•Internal carbon matrix was not corroded by melts due to the protective pyrocarbon.•Release of thermal stress produced defects and caused the loss of strength of sample.•The flexural strength can be improved by new deposition of pyrocarbon in defects.The carbon/carbon composites with Zr–Ti–C were prepared by liquid metal infiltration (LMI) process. The chemical corrosion and thermal stress damage of carbon matrices in Zr–Ti melts were investigated. A corrosion mechanism and a method of rehabilitating defective materials were proposed. The results indicated that the internal carbon matrices of composites were not corroded by the Zr–Ti melts and their vapours. However, the superficial matrices contacting the melts were severely consumed. In addition, the release of thermal stress produced the defects. The flexural strength of the samples after LMI could be improved via a new deposition of pyrocarbon in the defects.

The effects of fibre architecture, reaction temperature and holding time on the infiltration performance of carbon/carbon (C/C)–Zr–Ti–C composites prepared by liquid metal infiltration were investigated. The results indicated that samples with a chopped-web needled preform and low initial density had a high final density. Increasing the reaction temperatures resulted in a decrease of the final density of samples. Additionally, increasing the initial holding time appeared to obviously result in a high final density, but its effectiveness was not obvious in later observations. An analysis of the infiltration kinetics and mechanisms indicated that the diffusivity of carbon in the carbide, the open-pore sizes and their distribution in C/C composites were the essential characteristics that controlled the height of infiltrating melts.