Chapter 21: The Role of Pressure-Dependent Viscoplasticity and Volumetric Dilatation in Energetic Materials at Intermediate Strain Rates

The mechanical behavior of energetic aggregate materials (polymer bonded explosives, propellants, etc.) at low to intermediate strain rates is a complex function of the material constituents, manufacturing methods, and microstructure morphology. Shear-induced volumetric dilatation, similar to the characteristic behavior of granular materials and soils, can play a key role to open up porosity in the microstructure, particularly when the material is under some degree of confinement. We present a continuum modelling approach that accounts for this phenomena via a pressure-dependent viscoplastic extension to the classical ViscoSCRAM [1] constitutive model and use it to study the role of shear-induced dilatation in confined and unconfined material at a variety of strain rates. Modeling results are compared with intermediate strain rate Split Hopkinson Pressure Bar experiments and show good agreement between predicted and measured stresses.