Mechanical Response of ZrB2–SiC–ZrO2 Composite Laminate

Abstract

The paper deals with heat-reflecting ZrB₂–20% SiC ceramic composite and heat-reflecting ZrB₂–20% SiC composite laminate with ZrO₂ addition, the amount of which varies from 0 to 100%. Their properties and behavior are studied under the conditions of three-point bending and diametral compressive tests. The increased amount of ZrO₂ in the composite layers notably reduces the elastic modulus and increases the thermal-expansion coefficient. It is found that in the composite laminate layer adjacent to that with lower thermal-expansion coefficient and in the layer adjacent to that with higher thermal-expansion coefficient, compressive and tensile residual stresses appear, respectively. The hardness in the region of compressive stress is higher than in the region of tensile stress. The texture of the broken specimen surface indicates that the main crack bifurcation occurs at the interface of the layers with 30 and 70% ZrO₂ content and the greater difference in the thermal-expansion coefficient, regardless of the loading conditions of three-point bending. The fracture energy of ZrB₂–SiC–ZrO₂ composite laminate significantly exceeds that of ZrB₂–20% SiC ceramic composite.