Constitutive Modeling of High-Elongation Solid Propellants

A phenomenological approach is used to represent the nonlinear viscoelastic behavior of solid propellants. A three-dimensional finite strain viscoelastic model, modified by a strain softening function that accounts for damage effects, is considered in the research. Some of the significant aspects of high-elongation propellants are incorporated into the constitutive model. The resulting stress-strain relation is applied to a particular high-elongation propellant by means of the related material characterization. The response predicted by the model is compared with the experimental data for different loading conditions. The model predicts the propellant behavior quite well at uniaxial strain magnitudes up to 50 percent. Numerical analysis of very general geometries and loadings are possible, since a fully general model is calibrated.