The Role of Aluminum in the Detonation and Post‐Detonation Expansion of Selected Cast HMX‐Based Explosives

TLDR

The study investigates how 15 % aluminum (3.2 µm) versus inert lithium fluoride affects detonation and post‑detonation behavior in cast‑cured HMX formulations through cylinder and plate‑pushing experiments across different time regimes. Researchers performed small cylinder tests to measure detonation and wall velocities (1–20 µs), near‑field blast measurements with 58 mm spherical charges at 152 mm and 254 mm, pressure readings at 1.52 m, and hydrocode simulations to assess non‑ideal effects on plate test results. Aluminum‑containing formulations produced significantly higher wall and plate velocities and pressures at ≥2 µs, indicating that Al reactions after the Chapman–Jouguet plane continue to drive expansion up to ~2 ms, thereby enhancing detonation and blast effects.

Abstract

Abstract In order to improve understanding of how aluminum contributes in non‐ideal explosive mixtures, cast‐cured formulations have been analyzed in a series of cylinder tests and plate‐pushing experiments. This study describes the contribution of 15 % aluminum (median size of 3.2 μm) vs. lithium fluoride (an inert substitute for aluminum; <5 μm) in cast‐cured HMX formulations in different temporal regimes. Small cylinder tests were performed to analyze the detonation and wall velocities (1–20 μs) for these formulations. Near‐field blast effects of 58 mm diameter spherical charges were measured at 152 mm and 254 mm using steel plate acceleration. Pressure measurements at 1.52 m gave information about free‐field pressure at several milliseconds. While the observed detonation velocities for all formulations were within uncertainty, significantly higher cylinder wall velocities, plate velocities, and pressures were observed for the aluminum formulations at ≥2 μs. Additionally, hydrocode calculations were performed to determine how non‐ideal behavior affected the plate test results. Collectively, this work gives a clearer picture of how aluminum contributes to detonation on timescales from 1 μs to about 2 ms, and how the post‐detonation energy release contributes to wall velocities and blast effects. The experiments indicate that significant aluminum reactions occur after the CJ plane, and continue to contribute to expansion at late times.