Fabrication of short-fiber-reinforced SiC composites by polycarbosilane infiltration

Green sheets of the composites using polycarbosilane (PCS)-infiltrated (coated) Tyranno SA short fibers, submicron SiC powder and Al2O3–Y2O3–CaO mixtures as sintering additives were prepared by tape-casting. These green sheets were stacked and hot-pressed at 1750 °C. Most of all SiC short fibers were oriented along the tape casting direction. The bulk density of the composites was about 2.66 g/cm3. The bending strength was measured at room and high temperatures and the highest value was about 260 MPa at room temperature and 1000 °C. The fracture behavior of the composites showed a completely brittle fracture at room and high temperatures up to 1400 °C. Results of scanning electron microscope investigation showed that there were little pulled-out fibers in the tensile stress zone of the fracture surface independent of test temperature. A mechanically weak and chemically tight interface layer was not successfully formed by the present coat method.