Dynamic stress chain formation in a two-dimensional particle bed

Cure cast plastic bonded explosives (PBXs) consist of relatively hard particles in a soft binder. Under compressive loading, the explosive cyrstals come into contact that causes high stress concentrations. The lines along which the crystals are loaded are called stress chains. Damage done to these particle beds during compressive loading can lead to reaction. The photoelastic effect of PMMA is exploited to examine the stress state within a two-dimensional particle bed. Stress chain development within the bed is recorded and is shown to increase the stress state within some particles while leaving others unloaded. These concentrations form early in the loading process, leading to fracture along the stress bridges and generating likely reaction initiation sites. Through material point method simulations, contact friction is shown to have a large effect on the stress distribution within the particle bed.