Mechanical properties of unidirectional and crossply SiCf/SiC composites using SiC fibers with carbon interphase formed by electrophoretic deposition process

• Unidirectional (UD) and Crossply (CP) SiCf/SiC composites showed pseudo-ductile fracture behavior in bending test.
• Fiber orientation affects the mechanical properties of SiCf/SiC composites.
• CP-SiCf/SiC composites would be more attractive than UD-SiCf/SiC composites.
• EPD process is effective to form high-performance carbon interphases in SiCf/SiC composites.
• High-performance CP-SiCf/SiC composites would be achieved by the optimum microstructure design.

Unidirectional (UD) and crossply (CP) SiCf/SiC composites with different fiber volume fraction were fabricated based on EPD and sheet stacking process, and their mechanical properties were evaluated at room temperature. The UD-SiCf/SiC composites showed a pseudo-ductile fracture behavior in bending test. Bending strength and fracture energy of the UD-SiCf/SiC composites with high Vf (66%) was higher than those of the UD-SiCf/SiC composites with low Vf (47%). Although the CP-SiCf/SiC composites also fractured in a non-brittle manner, their bending strength and fracture energy were much lower than the UD-SiCf/SiC composites because the SiC fibers aligned in 90° direction did not work for toughening and strengthening the SiCf/SiC composites. In the UD-SiCf/SiC composites, fiber pullout was clearly observed, and the number of fiber pullout in the UD-SiCf/SiC composites with high Vf was large rather than the UD-SiCf/SiC composites with low Vf. On the other hand, fiber pullout did not appear in the CP-SiCf/SiC composites with low Vf whereas large number of fiber pullout was observed in the CP-SiCf/SiC composites with high Vf. This can be explained by the thickness of the SiC matrix-layers between SiC fiber-layers.