The effects of pyrolytic carbon interphase (PyC) thickness on the density, microstructure, and mechanical properties of continuous SiC fiber-reinforced SiC composites (SiCf/SiC) have been examined. Electrophoretic deposition combined with ultrasonication was performed to infiltrate a SiC-based matrix phase effectively into the fine voids of a Tyranno-SA SiC fabric preform, which was coated with PyC at thicknesses of 0, 200, 400, 600, and 800 nm. The density of the hot-pressed SiCf/SiC composites decreased with increasing PyC thickness because of the difficulty of matrix-phase infiltration into the fine voids of the preform. SiCf/SiC composites with PyC≤ 400 nm showed a brittle fracture mode due to the strong fiber-matrix interface, in spite of their relatively high flexural strength. On the other hand, toughened SiCf/SiC composites could be achieved with PyC ≥ 600 nm because of the formation of a weak interface, in spite of their decreased flexural strength.

Keywords: SiCf/SiC composites, Interphase, Mechanical properties, Fiber pullout.