COMPARISON OF THE UNIAXIAL TENSILE MODULUS AND DYNAMIC SHEAR STORAGE MODULUS OF A FILLED HYDROXY-TERMINATED POLYBUTADIENE AND GAP PROPELLANT

The uniaxial tensile moduli for two filled composite solid propellants , one based on a hydroxy-terminated polybutadiene with an ammonium per chlorate oxidizer and the other on a glycidyl azide polymer with a pha se-stabilized ammonium nitrate oxidizer, were measured at various temp eratures and over a three decade range of strain rates. Dynamic shear moduli were measured at various strains and temperatures over a three decade range of frequencies. Values of the tensile modulus, E(T)/3 (as suming Poisson's ratio equals 0.5), were compared with the dynamic sto rage modulus, G', for each of the dynamic strain levels investigated. The results demonstrate that it is possible to compare 3G' measured at different dynamic strains and frequencies with the incremental tangen t moduli obtained at corresponding uniaxial strains from constant stra in rate tests on specimens with a JANNAF geometry. The comparisons are most favourable when the concave-up region of the stress-strain curve extends only up to approximately 2.0% strain. It was observed that G' obtained at a dynamic shear strain of 2.0% provided the best overall correlation with E(T)/3 measured over a range of temperatures and stra in rates.