Dynamic strength and inelastic deformation of ceramics under shock wave loading

To gain insight into material strength and inelastic deformation of ceramics under plane shock wave loading, an in-depth study was carried out on polycrystalline silicon carbide (SiC). Two independent methods were used to determine experimentally the material strength in the shocked state: 1) lateral piezoresistance gauge measurements, and 2) compression and shear wave experiments. The two sets of data were in good agreement. The results show that the Poisson’s ratio of the SiC increases from 0.162 to 0.194 at the HEL (11.5 GPa). The elastic-inelastic transition is not distinctive. In the shocked state, the material supports a maximum shear stress increasing from 4.5 GPa at the HEL to 7.0 GPa at twice the HEL. This post-HEL strength evolution resembles neither catastrophic failure due to massive cracking nor classical plasticity response. Confining stress, inherent in plane shock wave compression, plays a dominant role in such a behavior. The observed inelastic deformation is interpreted qualitatively using an inhomogeneous mechanism involving both in-grain micro-plasticity and highly confined micro-fissures. Quantitatively, the data are summarized into an empirical pressure-dependent strength model.