Constitutive modeling of solid propellants for three dimensional nonlinear finite element analysis

A three dimensional constitutive model for solid propellants is proposed and implemented in a finite element software. The effects of viscoelasticity, large deformation, temperature, pressure, softening in monotonic and cyclic loadings are represented. Damage is assumed to initiate by failure of the particle-binder bond or failure in the binder itself. Opening of the micro-cracks resulting from either failure is associated with the evolution of damage. Stress softening during unloading and reloading is captured via a cyclic function modifying the viscoelastic stress. The implementation algorithm is stable and robust, therefore analysis of general geometries and loadings are possible. The model may be calibrated with a small number of test data, therefore is suitable for practical use in the industry.