Compressibility, Damage, and Age-Hardening Effects of Solid Propellants Using Finite Strain Constitutive Model

Abstract In this paper, the finite strain viscoelastic constitutive model for particulate composite solid propellants is proposed considering strain rate, large deformation/large strain, thermorheological behavior, stress softening due to microstructural damage, compressibility, and chemical age hardening. The compressible Mooney–Rivlin hyperelastic strain energy density function is used along with the standard model of viscoelasticity. To model the compressibility, the dilatational strain energy is taken as the hyperbolic function of the determinant of deformation gradient. The stress-softening phenomenon during cyclic loading (Mullin's effect) due to microstructural damage is described by an exponential function of the current magnitude of intensity of strain and its previous maximum value. The variation of material properties with time are studied using the isothermal accelerated aging technique through simulation and experimental investigation. The comparison of predictions based on the proposed model with the uniaxial experimental data demonstrates that the proposed model successfully captures the observed behavior of the solid propellants.