Shock Compression of Granular Powder: Experimental Design, Constraints, Motivation

Shockwave compression models for homogeneous materials are well understood, but models for the high-pressure shocked states reached in more complex materials are not so clear. Understanding how compressed materials behave is important for planetary impact modeling and materials science. We have designed a set of powder target shockwave experiments using a single-stage gas gun to test the hypothesis that smaller grain sizes, in granular ceramics, result in size-effect strengthening, causing a stiffer shocked response, which is supported by preliminary static compaction data. The design constraints of powder targets are presented: settling, lateral release waves, shock impedance mismatches, wave decay, and target characterization. Photon doppler velocimetry (PDV) will be a primary diagnostic for acquiring the shockwave profile, which should lend insight into the mechanisms (sliding, cleavage/comminution, twinning) responsible for the shocked response. The first powder experiments are scheduled for the summer of 2025, where granular ceramic powders, of equal composition but varying grain size distributions, will be shocked at several different impact speeds.