A Nonlinear Constitutive Relationship for Composite Propellants

The mechanical response and the failure of composite solid propellants are known to be related to the formation and growth of vacuoles on the microscopic or macroscopic scale. Failures in composite materials such as composite propellants originate at the filler particle or binder molecular level. These microscopic failures, whether adhesive failures between the binder and filler particles or cohesive failures in the binder, result in vacuole formation. The cumulative effect on all vacuole formation and growth is observed on the macroscopic scale as strain dilatation. The strain dilatation in composite propellants varies with binder type, binder formulation, filler particles, and presumably filler particle size distribution. The strain dilatation caused by vacuole growth and formation results in a nonlinear stress-strain behavior for these materials.