Solid rocket propellants are highly filled polymers and exhibit viscoelastic and rubber like elasticity. Concept of unique final modulus (H) for HTPB based solid rocket propellant is proposed and mathematical formulation based on third order polynomial fit for simulation of non-linear section of stress-strain curve is developed. Propellants are tested at different strain rates and temperature. It was observed that final modulus is independent of both strain rate and temperature. This indicates that after dewetting, mechanical behavior is not governed by fillers, strain rate or temperature. Additionally, with the help of proposed final modulus, complete stress-strain curve for propellant can be simulated at any temperature and strain rate. Non-linear portion of tensile testing curve is modeled using third order polynomial fit. Using a single additional parameter, simulation of complete stress-strain curves and dewetting strain is uniqueness and power of approach. Conventional mechanical properties parameters like initial modulus, tensile stress and percentage elongation at tensile strength changes with strain rate and temperature, but final modulus remain fixed and constant. It is in true sense an invariant material property.
solid rocket propellants, filled polymers, mechanical characterization, tensile test, elastic modulus.