This paper indicates the possibility of assessing the failure of a strip biaxial tension specimen from the non-linear stress-strain behaviour of a uniaxial tension specimen which is useful for characterizing the propellant material. In order to examine the adequacy of the analytical and finite element methods, test data existing on a HTPB-based propellant material is used, Failure predictions on a strip biaxial tension specimen are found to be in reasonably good agreement with test results.