An experimental study on dynamic deformation and ignition response of a novel propellant under impact loading

Investigations on high-energy and low-vulnerability propellants can provide a guarantee for improving the power and safety of solid rocket motors. In the present study, mechanical-thermal coupled responses were recorded by a high-speed infrared thermal imaging systems. The dynamic compressive properties and damage-ignition response mechanism under high strain rates of a novel type of propellant were studied, using a split Hopkinson pressure bar apparatus. The experimental results suggested that the mechanical properties of the novel propellant, in terms of yield stress, initial compressive modulus, and ultimate stress, were greatly affected by the loaded strain rate. The stress-strain responses exhibited an initial linear elasticity region, followed by yielding, and then a subsequent strain hardening or softening stage (plateau region), which was strongly dependent on the strain rate. It was found that the yield stress and ultimate stress increased with the strain rates. Moreover, the ignition response was accentuated at higher strain rates, resulting in an earlier and more intense ignition. According to the high-speed images and the post-test SEM images, the critical strain rate for ignition is 4500 s⁻¹. Finally, by calculating the bulk and local temperature rise (considering the friction mechanism), it is clear that the dominant ignition mechanism of the novel propellant is the friction which is macroscopically represented as viscous shear flow.