Cyclic thermal shock in SiC-whisker-reinforced alumina composite

Abstract

Cyclic thermal shock damage in SiC whisker-alumina ceramic-ceramic composites was monitored non-destructively via elastic modulus and internal friction measurements. Thermal-shock-damage-induced changes in internal friction were found to be a linear function of a crack damage parameter (which in turn is a function of crack density and crack size). The linear relation between internal friction changes and the damage parameter is explained if one assumes that internal friction is proportional to the integrated surface area of damage-induced cracks. Thermal shock damage, as measured by both elastic modulus and internal friction, was observed to saturate as a function of an increasing cumulative number of thermal shock cycles. This saturation damage level increases in proportion to ΔT p , where ΔT is the shock temperature difference. The exponent p has a value of approximately 6 for the range of ΔT included in this study. This power-law relation in ΔT implies a fatigue-like power-law relation in stress (or alternatively, a power-law relation in stress intensity K).