Effect of initial porous density on the shocked equation of state of granular aluminum oxide (Al₂O₃)

The shock compression response of granular or porous materials can differ greatly from that of solid materials. Aluminum oxide (Al₂O₃), also known as alumina, corundum, or sapphire in its single crystal form, is a hard and strong ceramic that is used in many engineering applications including abrasives, armors, and composite fillers. In prior studies, the shock Hugoniot of solid alumina has been evaluated; however, little work has been done on the dynamic compaction response of granular alumina. In this work, the effect of varying porosity on the equation of state of shock-compressed granular alumina is evaluated with initial densities at around 1.0, 2.0, and 2.5 g/cm³ (25, 51, and 63% theoretical max density, TMD) through a series of tamped Richtmyer-Meshkov instability (RMI) experiments. These experiments were performed at the Dynamic Compression Sector at the Advanced Photon Source Facility at Argonne National Laboratory with a single stage gas gun and the shock response was recorded using X-ray phase contrast imaging. The material interface and shock wave locations in each experiment were evaluated in time to obtain shock and particle velocities, characterizing the alumina Hugoniot equation of state as a function of initial porous density.