Abstract: To investigate the thermal aged properties of tri-component hydroxyl-terminated polybutadience (HTPB) propellant at low temperatures under dynamic quasi-biaxial loading, the quasi-biaxial tensile mechanical tests and scanning electron microscope (SEM) analysis are carried out at different thermal accelerated aging time, temperatures and strain rates. The results indicate that the tendency of stress-strain curves, variation of mechanical properties with loading conditions and fracture mechanism for the propellant are consistent with each other before and after aging. Moreover, the nonlinear relationships of the typical mechanical parameters and thermal aging time can be more reasonably described with the improved nonlinear model at the strain rates from 1 s -1 to 100 s -1 . As the temperature decreasing, the fracture mechanism of the aged HTPB propellant changes from dewetting to AP particles fracture. The coupled effects of the thermal aging, low temperature and high strain rate induce more serious damage of the propellant. However, the damage of the aged propellant under quasi-biaxial tension is weaker, compared with that at the same temperature and strain rate in uniaxial tension. The value of this mechanical parameter at -50 ℃ and 14.29 s -1 after aging for 32 d, 74 d and 98 d reduces to 28.79%, 27.58% and 25.63% of the value at room temperature and 0.40 s -1 before aging, respectively. Therefore, the maximal elongation of HTPB propellant under quasi-biaxial tension can be selected as the failure criterion for analyzing the structure integrity of the propellant grain for tactical missiles during ignition of SRM after long periods of storage.

Key words: Low temperature, Dynamic loading, Thermal accelerated aging, Solid propellant, Quasi-biaxial tension