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Interpreting and tailoring the dynamic mechanical response of granular systems relies upon understanding how the initial arrangement of grains influences the compaction kinetics and thermodynamics. In this article, the influence of initial granular arrangement on the dynamic compaction response of a bimodal powder system (soda-lime distributed throughout a porous, fused silica matrix) was investigated through continuum-level and mesoscale simulations incorporating real, as-tested microstructures measured with X-ray tomography. By accounting for heterogeneities in the real powder composition, continuum-level simulations were brought into significantly better agreement with previously reported experimental data. Mesoscale simulations reproduced much of the previously unexplained experimental data scatter, gave further evidence of low-impedance mixture components dominating shock velocity dispersion, and crucially predicted the unexpectedly high velocities observed experimentally during the early stages of compaction. Moreover, only when the real microstructure was accounted for did simulations predict that small fractions of the fused silica matrix material would be driven into the β -quartz region of phase space. These results suggest that using real microstructures in mesoscale simulations is a critical step in understanding the full range of shock states achieved during dynamic granular compaction and interpreting solid phase distributions found in real planetary bodies. [ABSTRACT FROM AUTHOR]

In this work, the in-fiber shock propagation in Dyneema® has been studied such that the shock propagated along the axis of one of the fiber directions. A fast moving precursor wave was detected that corresponded to the elastic wave velocity of the fibers suggesting that the fibers themselves were acting as wave guides. Further, it was noticed that above a threshold shock stress of ca. 3.5 GPa, this wave was not discernable. This shock stress corresponded with the stress at which shock-induced melt would be expected to occur suggesting that melting inhibited the fibers' ability to act as wave guides. [ABSTRACT FROM AUTHOR]