Constitutive modeling of deformation-environment coupled damage and failure in solid propellants

Understanding and quantifying the coupled effects of mechanical loading and environmental degradation in solid propellants are crucial for predicting reliability and structural safety of solid rocket motors in industrial applications. This study presents a unified viscoelastic constitutive model capable of consistently describing progressive damage and failure in propellants arising from both deformation and environmental effects. The framework is characterized by the following key features: (i) A single deformation energy combined with a damage-potential threshold governs the onset and evolution of damage without additional empirical functions or ad hoc internal variables, while a strain energy density-based criterion quantitatively links cumulative damage to ultimate failure. (ii) Deformation-induced damage is attributed to the breakage of matrix chains resulting in particle/matrix interface debonding and microcrack growth within the matrix; and environment-induced degradation enters through evolving material parameters reflecting competing crosslinking and scission mechanisms. (iii) The failure criterion incorporates the contributions of both glassy and rubbery states as well as the degradation associated with environmental factors. Implemented in ABAQUS, the model accurately reproduces rate and temperature-dependent responses of solid propellants under uniaxial, cyclic, and multiaxial loadings. Additional validation against pre-strained thermal aging experiments further confirms its predictive capability. Given its ability to capture coupled damage, environmental effects, and failure with a relatively small set of parameters, the proposed model offers efficient modeling approaches for the stress analysis of both pristine and aged propellants.