Influence of Fiber Volume Fraction on the Mechanical and Thermal Properties of Unidirectionally Aligned Short-Fiber-Reinforced SiC Composites.

The aim of this study were to fabricate a short-fiber-reinforced SiC composites by hot-pressing using an Al2O3-Y2O3-CaO mixture as sintering additive, and, to investigate the effect of processing parameters on the mechanical and thermal properties of SiC/SiC composites containing BN-coated Hi-Nicalon short fibers. Fibers were mostly aligned within planes perpendicular to the hot-pressing direction. The composite fabricated by this process achieved nearly full density after hot-pressing at 1700°C. The bending strength increased with increasing sintering temperature and decreased with increasing testing temperature. The fracture behavior of the SiC/SiC composites showed a completely brittle fracture. Results of scanning electron microscopy (SEM) investigation showed that there were pulled-out fibers in the tensile stress zone of the fracture surface, but the degree of pull-out was low. On the basis of these results, the influence of fiber volume fraction on the mechanical and thermal properties of the SiC/SiC composites is discussed.