Quasi–static studies of the deformation and failure of PBX 9501

This paper examines the influence of microstructure on the quasi–static failure of PBX 9501, a polymer–bonded explosive (PBX) manufactured for the Los Alamos National Laboratory in America. Optical microscopy has been used to examine qualitatively cracked and pristine material. Consequent on the manufacturing process, the explosive crystals display angular features and natural facets. In addition, considerable growth twinning, internal defects and voidage has been observed. These defects are found significantly to alter the failure path. In common with other PBXs, failure paths tend to run around the long straight edges of the explosive filler and avoid regions of fine filler and binder. Explosive crystals were found to fracture due either to cracks propagating from another region or internal defects. These observations are confirmed by the use of high–resolution moiré interferometry. This sensitive optical technique allows the deformation of the sample to be measured up to and including the point of failure. By taking white–light micrographs that are in exact registration with the measured displacement maps, the influence of the underlying microstructure can be seen.

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