Thermoelastic Anisotropy in SiC, Residual Stresses in Monolithic SiC Ceramics and SiC Whisker Reinforced Composites

Thermoelastic anisotropy of the (3C) and the (6H) polytypes of SiC is reviewed and presented in terms of a crystallographic thermoelastic stress index. The implications of this anisotropy are then applied through a modified Eshelby method to calculate the internal micromechanical stresses associated with large alpha-SiC (6H) grains in a beta-SiC (3C) marix and also for composites of single crystal (3C) SiC whiskers in several ceramic matrices. These internal stresses depend on thermal expansion differences; elastic modulus differences; the grain or crystal shape; the volume fraction of second phase. These stresses can be significantly amplified by external stresses. 25 refs.