Thermal Shock damage and Residual Strength Behavior of a Functionally Graded Plate with Surface Cracks of Alternating Lengths

Abstract

Multiple surface cracking greatly influences the thermal shock behavior of ceramics and ceramic composites. This work aims to investigate the effects of surface crack morphology coupled with material gradation on the thermal shock damage and residual strength behavior of functionally graded ceramics. We consider a functionally graded plate with an array of periodically spaced surface cracks of alternating lengths subjected to thermal shocks. The coupled strongly singular integral equations for the opening displacements along the long and short cracks are derived using the Fourier transform and a superposition technique. Thermal shock damages (arrested lengths of the long and short cracks) in the specimen and the residual strength are determined using the stress intensity factor criterion. Numerical results for an Al2O3/Si3N4 graded material are presented to examine the effects of initial crack length ratio, crack spacing, and material gradation on the thermal shock damage and residual strength behavior. It is found that surface crack morphology in combination with thermal property gradation significantly influences the thermal shock damage and residual strength behavior of functionally graded ceramics. The specimens with smaller initial crack length ratios suffer severer damages and strength degradation at moderately intense thermal shocks.