The relationship between tensile strength and flaw-size of silicon carbide single fibers

The fracture surfaces of SiC single fibers after tensile testing were observed by SEM. The resultant fracture typically showed the fracture origin-mirror-mist-hackle-crack branching morphology characteristic of brittle fracture of glassy materials. It was found that the fracture of the fibers mainly initiated from the surface flaws, which were semi-elliptical; the ratio of the depth to the width was about 0.3. The fracture toughness KIC was calculated from the tensile strength-flaw size relation, and was about 1.55 MPa m 1/2. The distributions of the depth and the width of the surface flaws at fracture origins, calculated from the Weibull's parameters and the fracture toughness KIC, were in good agreement with the experimental results.