Mesoscale shock structure in particulate composites

TL;DR

This paper investigates the mesoscale shock response of particulate composites using high-speed digital image correlation and simulations, revealing heterogeneous shock structures and mechanisms like wave scattering and interface reflections.

Contribution

It introduces the first application of full-field high-speed DIC to study mesoscale shock behavior in particulate composites, combining experiments with simulations for detailed insights.

Findings

Shock thickness decreases with increasing stress.

Heterogeneous mesoscopic response causes rough shock fronts.

Reflections and wave interference at interfaces drive shock roughness.

Abstract

Multiscale experiments in heterogeneous materials and the knowledge of their physics under shock compression are limited. This study examines the multiscale shock response of particulate composites comprised of soda-lime glass particles in a PMMA matrix using full-field high-speed digital image correlation (DIC) for the first time. Normal plate impact experiments, and complementary numerical simulations, are conducted at stresses ranging from $1.1-3.1$ GPa to elucidate the mesoscale mechanisms responsible for the distinct shock structure observed in particulate composites. The particle velocity from the macroscopic measurement at continuum scale shows a relatively smooth velocity profile, with shock thickness decreasing with an increase in shock stress, and the composite exhibits strain rate scaling as the second power of the shock stress. In contrast, the mesoscopic response was highly heterogeneous, which led to a rough shock front and the formation of a train of weak shocks traveling at different velocities. Additionally, the normal shock was seen to diffuse the momentum in the transverse direction, affecting the shock rise and the rounding-off observed at the continuum scale measurements. The numerical simulations indicate that the reflections at the interfaces, wave scattering, and interference of these reflected waves are the primary mechanisms for the observed rough shock fronts.