Multiscale compaction behavior of granular composites

This study presents a multiscale experimental investigation and characterization of the formation and propagation of compaction waves in an energetic material simulant, polymer-bonded sugar (PBS), under impact loading. Local and macroscale deformation measurements during loading were performed using ultrahigh-speed photography combined with digital image correlation (DIC). The compaction wave velocity and propagation parameters were calculated from macroscale experiment data. A weak-shock-type compaction profile with a smooth front was observed at intermediate impact velocities. After a brief period of relatively stable compaction propagation, the wavefront was observed to widen as it propagated. Mesoscale measurements revealed a rough compaction front resulting from the formation of force chains, local viscous flow of the binder, and crystal fracture. The widening of the compaction wave is attributed to energy dissipation caused by viscous binder flow and local crystal fracture. Crystal fractures occurred at relatively low average stress levels and were associated with the formation of force chains. Finally, the effects of impact velocity and volume fraction on local deformation mechanisms during compaction wave formation are discussed.