An improved dynamic constitutive model for ceramics

An accurate constitutive model for ceramic is essential for guiding its application in armor systems. Inspired by previous work, an improved dynamic constitutive model for ceramics is developed. In the constitutive model, a new equation of state is proposed by modifying the polynomial equation of state; the strength surface takes into account pressure dependency, strain rate effect, Lode effect, strain hardening and softening. To validate the present model comparisons are made between the model predictions and the material test data for alumina ceramics in terms of strength surface, strain rate effect, and pressure-volumetric strain relationship, and good agreement is obtained. Furthermore, numerical simulations using the present model are conducted, which cover a wide range of impact scenarios and impact velocities (namely, spalling of a long round bar, planar impact, pure ceramic target perforation, dynamic indentation, and projectile impact on ceramic composite armor). Comparisons are made between the numerical results and the experimental data for two similar alumina ceramics (i.e., AD995 and C98 ceramic) in terms of spalling position, particle velocity-time history, longitudinal wave velocity, Hugoniot elastic limit (HEL), residual velocity, cratering size, cracking pattern, and target deflection, and good agreement is also obtained, which lend further support to the accuracy and usefulness of the improved dynamic constitutive model for ceramics.