Analysis of tensile strength and fracture toughness of ZrB2–SiC ceramic from three-point bending samples with edge cracks

Abstract

ZrB2–SiC ceramic is one of most promising high temperature resistant materials in the field of thermal protection, and its strength and toughness are two key mechanical indicators which determine its application prospects. How to conveniently and accurately obtain its strength and toughness is of great value for engineering applications. In this paper, the tensile strength and fracture toughness of the ZrB2–SiC ceramic were obtained according to the boundary effect model (BEM) from a series of three-point bending tests of ZrB2–SiC ceramic samples. Then, the BEM method and normal distribution methodology were employed for analysis of strength and toughness of ZrB2–SiC ceramic. Results show that there exists a linear relationship between maximum loads Pmax and effective area Ae, and the slope of the straight line passing through the coordinate origin is the tensile strength ft. The tensile strength ft and fracture toughness KIC of ZrB2–SiC ceramic can be predicted simply from a set of three-point bending tests according to the BEM method. Similarly, the maximum loads Pmax for three-point bending samples can also be predicted and determined when the ft, KIC and average grain size are available. Results indicate that the grain sizes, ft and KIC of the ZrB2–SiC ceramic follow the law of normal distribution. Satisfactory results of the predicted ft and KIC between the upper and lower bounds with 95% reliability can be achieved based on BEM method.