Evaluation of <i>R</i>-Curve Behavior in SiC Particle-Dispersed Al<sub>2</sub>O<sub>3</sub> Composite

Abstract

Fracture resistance behavior with respect to crack extension is evaluated from indented strengths for both alumina and alumina matrix composite dispersed with 10% SiC particles. Since residual stresses due to the thermal expansion mismatch between SiC particle and Al2O3 matrix are expected to be exerted on crack surfaces regardless of crack length, the fracture resistance are assumed to be dependent on the square root of crack extension according to fracture-mechanical predictions. R-curves are obtained from the linearity between Vickers-indented strength and αf-1/2, where αf is the critical crack length. A nearly constant fracture resistance curve is obtained for the alumina, while rapidly increasing fracture resistance for the composite. The fracture toughnesses measured independently by the controlled surface flaw method are consistent with the obtained fracture resistance. The role of residual stresses is discussed as a characteristic parameter for the fracture resistance of particle-dispersed composites. In addition, the technical aspects during the evaluation process of R-curve are also discussed.