Silicon carbide nanofibers (SiCNFs) used as the second reinforcements of carbon/carbon composites were grown radially on the carbon fiber surface. The microstructure of SiCNFs and their effects on the microstructure and flexural properties of C/C composites were investigated. Results show that there are many defects such as twin crystals and stacking faults in SiCNFs which were grown by catalytic chemical vapor deposition. During the same process, the skin region of carbon fiber has changed. Several SiC layers are formed and the arrangement of the graphite layers around SiC layers is more orderly. In the next chemical vapor infiltration, due to the induction of SiCNFs, the middle textural pyrocarbon were formed firstly and then is the high textural pyrocarbon. The existence of SiCNFs also contributes to the three-phase interface between pyrocarbon, SiCNFs and carbon fibers, resulting in a good bond between carbon fiber and matrix. Those structural changes lead the better flexural properties of SiCNF–C/C composites compared with C/C composites.

Carbon fibre-reinforced carbon and silicon carbide dual matrix composites (C/C-SiC) were fabricated by a combination of chemical vapor infiltration with liquid silicon infiltration. The structural characteristics, mechanical performance and tribological properties of the C/C-SiC composites and their wear mechanism at different braking speeds were investigated using a QDM150 friction testing machine, SEM and x-ray energy dispersive analysis. Results indicate that the C/C-SiC composites show an increased bonding strength at the fibre/matrix interface, and the value of flexural strength and compressive strength of the C/C-SiC composites can reach 240 and 210 MPa, respectively. The friction coefficients are between 0.41 and 0.54. Wear rates are not sensitive to the brake speed and remain constant at about 0.02 cm3/MJ, and the friction coefficient is stable. Frictional films with a thickness of 1∼3 μm are formed on the worn surface of the composites upon braking. The wear mechanism changes with increased braking speed, from abrasion at 8m/s, adhesion at 12 m/s and 16m/s to fatigue and oxidation at 20 m/s and 24 m/s, respectively.