A Constitutive Formulation for High-Elongation Propellants

A constitutive model is presented that appears to successfully represent the stress-strain behavior of a highelongation propellant over a wide range of conditions. The model uses a Lagrangian formulation and separates the propellant response into shearing and volumetric components. Particular features of the model are the use of a strain-softening function multiplying a convolution integral that is analogous to that of linear viscoelasticity. Within the integral is an additional term that modifies the history effects. This term appears to correlate behavior at changing strain rate with that at changing temperature. Comparisons with experimental data are given.