Thermoviscoelastic Characterization of a Composite Solid Propellant Using Tubular Test

Abstract

The accurate thermoviscoelastic characterization of a solid propellant is critical for optimum design of grains for high-performance solid motors for space applications. A more realistic experimental method is reported for the characterization of propellants at multiaxial stress conditions using a grain-pressurization test called the tubular test. An idealized cylindrical grain with hydroxyl-terminated-polybutadiene-based propellant is used. From the measured outer radial expansion of the tubular specimen, creep compliance and the relaxation modulus of the propellant are computed based on linear viscoelastic theory. The relaxation-modulus data obtained from the tubular test are shown to be higher than the traditional uniaxial and strip biaxial tests at the same strain level. Different isothermal tubular tests are carried out at various strain levels, and master curves are generated. The tubular test with internal pressurization is found to be an easier, more inexpensive, and realistic method for predicting the relaxation-modulus values of solid propellants and to have great potential for the thermoviscoelastic characterization of solid propellants.