On weak influence of aluminum powder size on its post-detonation reaction in different time scales

The outstanding performance of aluminized explosives is attributed to the substantial energy released through aluminum (Al) reactions during post-detonation flow. However, the influences of Al powder size on the explosion power of aluminized explosives sometimes vary significantly across different time scales, which may suggest potential differences in Al reaction processes. To investigate the size-dependent reaction behavior of Al powders at different time scales, a novel experimental apparatus was employed to measure the velocity of a rod propelled by the detonation products of RDX/Al explosives (with Al powder sizes of 1.9 µm or 47.1 µm)1 at ∼1 ms, and the results were compared to those obtained from previous tube tests at around 30 µs. The experimental findings reveal that the impact of Al powder size on the metal-driven capability of aluminized explosives is not substantial at either 1 ms or 30 µs. Given the inadequacy of the phenomenological equation of state for studying the Al reaction due to its inability to ensure the uniqueness of the reaction process, we investigated the tburn∝dAln law using the Gurney energy method, where dAl and tburn denote the powder size and combustion time of Al powders, respectively. The values of n (0.031 and 0.038) were examined for the first time in post-detonation flow, which are significantly smaller than those observed in quasi-static flow. These results substantiate that the weak powder size effect on Al reaction is likely a prevalent phenomenon for micron-sized Al powders in post-detonation flow, attributable to the high pressure and high velocity characteristic of such flows.