Mechanical Strength of Ceramic Fibers

The mechanical properties of the silicon carbide (SiC)_fiber/SiC_matrix composite materials are basically dominated by the strength of the SiC fibers. The strengths of all SiC-polycrystalline fibers are about 3 GPa. To improve the mechanical strength of ceramics, a better understanding of the relationship between defects and strength is very important. Using Tyranno SA fiber as an example, the chapter describes the detailed information regarding microstructure and mechanical strength of ceramic fibers. Tyranno SA is a nearly stoichiometric SiC-polycrystalline fiber. In the production process of Tyranno SA, to achieve the stoichiometric composition of SiC crystal, the degradation reactions of an intermediate fiber and the subsequent sintering of the degraded fiber are effectively performed. Though these degradation reactions have to be absolutely performed for achieving the stoichiometric composition, partly anisotropic reaction in some filaments result in the aforementioned carbon-rich regions.