Indentation Fracture Response and Damage Resistance of Al ₂ O ₃ ‐ZrO ₂ Composites Strengthened by Transformation‐Induced Residual Stresses

Abstract

Indentation fracture behavior of three‐layer Al 2 O 3 ‐ZrO 2 composites with substantial compressive residual stresses was compared with the behaviors of monolithic Al 2 O 3 and Al 2 O 3 ‐ZrO 2 ceramics without intentionally introduced residual stresses. The indentation cracks were smaller in the three‐layer specimens relative to the monolithic specimens in agreement with the predictions of indentation fracture mechanics theory. Indentation and strength testing were used to show that a residual compressive stress of approximately 500 MPa exists in the outer layers of the three‐layer composites. The three‐layer specimens showed excellent damage resistance in that the strength differential between the three‐layer and monolithic indented specimens was maintained at indentation loads up to 1000 N, the maximum indentation load used in the experiments.