Significance of Non-Linear Stress-Strain and R-Curve Behaviour on Thermal Shock of Ceramics

Abstract

Observations are presented that show compelling evidence for the importance of non-linear elastic behaviour of ceramic and refractory materials if they survive severe thermal shocks. It is also shown that these same materials exhibit significant R-curve behaviour due to a number of mechanisms, with the most thermal shock resistant exhibiting the most extended toughness increment over a considerable crack extension. It has been found for a number of composite materials that the strength and thermal shock resistance correlates with a so called internal stress intensity factor. A simple fracture mechanics relationship is developed that attempts to explain a number of the observed effects, including the onset of non-linear behaviour, the strength of the composite and the thermal shock resistance of such materials. An additional feature is the predicted specimen size dependent thermal shock behaviour of ceramic materials which is similar to observations.