Uniaxial and Quasi-Biaxial Tensile Mechanical Properties of Aged HTPB Propellant at Low Temperatures Under Dynamic Loading

A comprehensive research endeavor was undertaken to investigate the mechanical behavior of aged solid propellants subjected to low-temperature dynamic loadings. This endeavor encompassed the evaluation of the stress–strain responses and the dissection of the tensile fracture attributes of HTPB propellant across an extensive temperature spectrum (−30 °C to 25 °C) and diverse strain rates (ranging from 0.4 s−, 4.0 s−, to 14.29 s−1). The methodology integrated uniaxial and biaxial tensile tests with microstructural analysis of fracture surfaces via electron microscopy. Our observations revealed that the aged HTPB propellant exhibited consistent tensile behaviors in both quasi-biaxial and uniaxial configurations, which were markedly influenced by temperature variations and strain rate alterations. It is noteworthy that as temperatures decreased and strain rates increased, a significant improvement in mechanical resilience was observed. Notably, the failure mode of the HTPB propellant shifted from dehumidification-driven effects to granular rupture. Both the initial elastic modulus and ultimate tensile strength demonstrated a concordant surge with decreasing temperatures and accelerating strain rates, exhibiting a distinct linear-logarithmic correlation with strain rate. Furthermore, interrelationships between quasi-biaxial and uniaxial deformations under diverse loading scenarios were established, facilitating the anticipation of quasi-biaxial tensile properties based on uniaxial test outcomes alone.