Mesoscopic deformation features of shocked porous ceramic: Polycrystalline modeling and experimental observations

Abstract

To prevent functional failure, the macroscopic shock response of ceramics needs to be understood. We explored the mesoscopic deformation features of porous ceramics, which are responsible for the measured macroscopic “plastic” wave profiles, using polycrystalline modeling and experiments. A polycrystalline model is established that considers the influence of two major microstructures (multi-voids and grain boundaries) in the porous ceramics. Shock experiments with the recovery of shocked porous lead zirconate titanate ceramics were conducted. The computational results show that shear cracks nucleate around voids under shock because of severe shear stress concentrations. Broken fragments fill the voids and lead to void collapse. Representative long-distance extended cracks and thick crevices are observed in the recovered sample subjected to 3.3 GPa compression. These representative features are reproduced by the polycrystalline model. An initial transgranular crack translates into an intergranular crack after a certain propagation range to form a long-distance extended crack. Intergranular cracks branch from the main transgranular crack during main crack propagation to form a thick crevice. The simultaneous propagation of main and branching cracks results in a more effective shock energy dissipation. Slippage and rotation deformation induced by multi-cracks allows the shocked porous ceramic to deform even after all the voids have collapsed. Mesoscopic deformations of porous ceramics induce significant stress relaxations and lead to macroscopic “plastic” wave profiles. The polycrystalline model will aid microstructures design and provide guidance for preventing the shock failure of functional ceramics.