High temperature tensile damage behavior of ZrB₂-based ultra-high temperature ceramic composites

The tensile property tests of SiC(20vol%)-graphite(15vol%)/ZrB₂ composites were carried out at room and high temperatures. The reduction of tensile strength and elastic modulus, and the obvious nonlinear behavior for composites were observed at high temperatures. The attenuation law of elastic modulus with temperature was characterized by introducing thermal damage. The mechanical damage evolution equation under the uniaxial stress was determined through the statistical analysis of strength, and then a high temperature tensile damage nonlinear constitutive model was presented under the thermal-mechanical coupling conditions. The results show that, with the increase of temperature, the thermal and mechanical damage of SiC-graphite/ZrB₂ composites increase as well as the ductility, and the transition temperature which range from brittle fracture to ductile fracture is 1 250-1 350℃.