Abstract: The tensile properties of HTPB solid propellants in the wide temperature (-70 ℃~70 ℃) and loading speed (2~200 mm/min) range are experimentally studied, and the temperature and strain rate dependent failure envelopes are obtained. Furthermore, the failure envelope evolution of propellants is studied by using a cyclic load to mimic the air based repeated cruise condition. Our results show that the failure envelope of propellants satisfies the equivalence principle. With the increase of loading speed, the failure envelope horizontally moves towards the high temperature, resulting in a decrease of the low temperature reliability for the solid motor. After experiencing the cyclic loads, the failure envelope vertically moves toward the small fracture elongation, resulting in a significant reduction of the reliable launch area. This paper provides a method supporting the design and the reliability analysis of solid rocket motor under actual service conditions.

Key words: HTPB solid propellants, Failure envelopes, Equivalence principle, Reliability analysis