Mechanical properties and thermal shock resistance of anisotropic ZrB₂-SiC-graphite ceramic

The anisotropic mechanical properties of ZrB₂-SiC-graphite ceramic were caused by adding graphite flakes, corresponding to the hot pressing axis. Flexural strength and elastic modulus in the directions parallel and perpendicular to hot pressing axis were measured by the three-point bending tests, respectively. Thermal shock resistance was predicted under cooling by the theory and the finite element methods in different directions. The temperature and thermal stresses fields of ZrB₂-SiC-graphite were calculated to analyze failure under cooling. Results show that, flexural strength and elastic modulus reduce by 41.47% and 36.9% respectively in the direction perpendicular to graphite flake, in comparison to those in the direction parallel to graphite flake. The stress is higher than the experimental strength and leads to the failure in the direction perpendicular to graphite flake.