Abstract
It is known that the CFCCs (continuous-fiber-reinforced ceramic matrix composites) are characterized by their non-linear fracture behavior, which is hardly found in monolithic ceramic materials. In order to develop materials for high temperature services, a sintered SiC (Tyranno-SA) fiber-reinforced oxide matrix composites were fabricated by using a slurry infiltration method and hot-pressing. As a result, MAS glass matrix composite with 50% Vf. of the fiber and a density of 2.84 g/cm^3 was obtained. As the mechanical properties at room temperature, the three-point flexural strength and quasi-static adsorbed energy.were 500 MPa and 6,000 J/m^2, respectively. Without graphite or an h-BN precoating on the surface of the fiber, pull-out and bridging of the fibers from the matrix was found, and this leads to a high value of the adsorbed energy. By TEM observation, nano-scale crystalline products were found between the fibers and the glass matrix. The push-out test reveals that this layer causes the appropriate debonding of the interface during the fracture process of the composite. Furthermore, eutectic composition of a sintered Al_2O_3-YAG matrix composite was fabricated. In order to control the interfacial strength between SiC fiber and the matrix, 1 μm thickness of a CVD-graphite (Pyrograph, TOYO TANSO Co. Ltd.)_was coated on the fiber. The-flexural strength and the adsorbed energy were 580 MPa (at R.T.), 760 MPa (at 1573K) and 11,200 J/m^2 respectively. In spite of these excellent mechanical properties, transverse crack in the matrix was inevitable which was caused by thermal residual stress after hot-pressing. This crack has a possibility to deteriorate the anti-oxidization ability of the material.
