The failure mechanism of ZrB₂-SiC-graphite composite heated by high electric current

The failure mechanism of the ZrB₂-SiC-graphite composite heated by high electric current was investigated. The results indicated that a large numbers of graphite flake was torn along their basal planes, which was attributed to that the thermal stress is perpendicular to graphite flake. The thermal stress resulted from the thermal expansion mismatch during rapid heating was calculated to be above 1.5 GPa using Hsueh's formula. Although the thermal stresses were relaxed through the deformation of graphite, the maximum thermal stresses were higher than the strength of < 500 MPa for the ZrB₂-SiC-graphite composite, which resulted in the destruction of the specimen.