Measuring Propellant Stress Relaxation Modulus Using Dynamic Mechanical Analyzer

A method for determining the stress relaxation master curve of solid rocket propellants was developed. The propellant was tested in uniaxial tension, using a conventional approach, and also in a dynamic mechanical analyzer, using a dual cantilever beam mode. While the results were similar, the dynamic mechanical analyzer required less material, resulted in reduced variability, and was not sensitive to the applied strain. The quantity of material required was on the order of grams, so that results were obtained with small amounts of propellant, as compared to the conventional uniaxial tension test that requires material quantities on the order of kilograms. Some important considerations also discussed include the verification of strain independence before testing and the loosening of clamps between temperatures during testing.