Size‐Scaling of Tensile Failure Stress in a Hot‐Pressed Silicon Carbide

Quasi‐static Weibull strength‐size scaling of hot‐pressed silicon carbide is described. Two surface conditions (uniaxial ground and uniaxial ground followed by grit blasting) were explored. Strength test coupons sampled effective areas from the very small (4 × 10 −3  mm 2 ) to the very large (4 × 10 4  mm 2 ). Equibiaxial flexure and Hertzian ring crack initiation were used for the strength tests, and characteristic strengths for several different specimen geometries were analyzed as a function of effective area. Characteristic strength was found to substantially increase with decreased effective area for both surface conditions. Weibull moduli of 9.4‐ and 11.7 well‐represented strength‐size scaling for the two ground conditions between an effective area range of 10 −1 and 4 × 10 4  mm 2 . Machining damage was observed to be the dominant flaw type over this range. However, for effective areas <10 −1  mm 2 , the characteristic strength increased rapidly for both ground surface conditions as the effective area decreased, and one or more of the inherent assumptions behind the classical Weibull strength‐size scaling were in violation in this range. The selections of a ceramic strength to account for ballistically induced tile deflection and expanding cavity modeling are considered in context with the measured strength‐size scaling. The observed size‐scaling is briefly discussed with reference to dynamic strength.