Interfacial control of uni-directional SiCf/SiC composites based on electrophoretic deposition and their mechanical properties

Interfacial control of uni-directional SiCf/SiC composites were performed by EPD, and their mechanical properties at room temperature were evaluated. The effect of the thickness of carbon interphase on SiC fibers by EPD on mechanical properties of uni-directional SiCf/SiC composites was also investigated. The average thickness of carbon coating on SiC fibers increased from 42 nm to 164 nm with an increase in the concentration of colloidal graphite suspension for EPD. Dense SiCf/SiC composites were achieved and their fiber volume fraction was 47–51%. The SiCf/SiC composites had a bending strength of 210–240 MPa. As the thickness of carbon coating was below 100 nm, the SiCf/SiC composites (SC01 and SC02) fractured in almost brittle manner. In contrast, the SiCf/SiC composites (SC03) showed a pseudo-ductile fracture behavior with a large number of fiber pullout as the thickness of carbon coating was above 100 nm. The fracture energy of SC03 was 3–4 times as high as those of SC01 and SC02 and the value was about 1.7 kJ/m2. In consideration of the results of mechanical properties, the thickness of carbon coating on SiC fibers should be at least 100 nm to obtain high-performance SiCf/SiC composites. The fabrication process based on EPD method is expected to be an effective way to control the interfaces of SiCf/SiC composites and to obtain high-performance SiCf/SiC composites.