High rate response and dynamic failure of structural ceramics

The process of dynamic failure of four structural ceramics subjected to unconfined uniaxial dynamic compression is investigated. The four materials examined are α-SiC, AD995 Al₂O₃, β-Si₃N₄, and SiAlON. In each case, the dynamic failure process is studied through dynamic loading of cylindrical specimens within a compression Kolsky bar combined with high-speed photography. Strain rates in the range of 10³ s^-1 are achieved (the corresponding loading rates are on the order of 200 MPa/μs). The dynamic failure process for all four ceramics consists of the development and propagation of axial splitting cracks followed by columnar fragmentation. Macroscopic cracks (propagating with crack velocities of several hundred meters per second) and substantial volumetric strains are observed well before the peak strength is attained.