Abstract: 3D carbon fiber reinforced silicon carbide matrix composites (C_f/SiC) were fabricated by vapor silicon infiltration (VSI) at 1650℃. Densities of the composites with or without C/SiC interphase are about 1.85g/cm³. The characterization of the C_f/SiC composites was investigated. When C/SiC interphases exist, the carbon fibers are protected from the reaction with silicon gas and the fibers remain intact. The fiber-matrix bonding is weakened and the distinct fiber pull-outs occur in C_f/SiC composites with interphases. The composite shows non-brittle fracture behaviour and its flexure strength reaches around 239.5MPa. However, the C_f/SiC composite without interphase has very poor mechanical performance. Its flexure strength is only 67.4MPa. Results indicate that the carbon fibers are siliconized during vapor silicon infiltration without interphase. When the vapor infiltration temperature increases to 1700℃, density of C_f/SiC composites with interphase increases to 2.25g/cm³. Strength of this composite is nearly the same as that fabricated at 1650℃

Key words: C_f/SiC, vapor silicon infiltration, interphase