Dynamic stress bridging in granular material

Through numerical experiments we investigate stress localization in granular material with application to plastic-bonded explosives. The results shed light on static versus dynamic loading, and on the role of an interstitial material between grains. Under static loading, we observe stress localization and bridging in a lattice of polydisperse cylinders in two dimensions. Under dynamic loading, we observe a two wave structure with stress fingers propagating ahead of a normal compaction wave. When an interstitial material is added (a polymeric binder), force fluctuations are substantially reduced under both static and dynamic loading. Under dynamic loading, the structure of the stress wave depends upon the material properties of the binder. As the binder stiffness increases, stress fingering decreases and is replaced by a planar compaction wave. (C) 1998 American Institute of Physics. [S0021-8979(98)10310-9].