Morphological characterization and elastic response of a granular material

The granular structures of energetic materials made of hexogene particles embedded in a matrix are characterized using a combination of flotation, light-scattering measurements and micro-computed tomography images. The complementary nature of the three characterization techniques, when employed with this type of material, allows one to derive accurate estimates for the grain size distribution and the particle bulk density distribution. Three types of granular formulations, with the same weight fraction of particles but markedly different grains morphology and shock-sensitivity properties, are addressed. The particles granulometry and intra-granular porosities differ from one material to another. The grains spatial dispersion in the three formulations, characterized by the scale-dependent local density, also varies from one formulation to another. Specifically, we show that samples containing elongated grains display "abnormal" variance scalings for the grains local density, as a result of long-range correlations in the granular packing structure. The use of virtual microstructures to predict the materials mechanical properties is addressed and discussed.