Tailoring impact debris dispersion using intact or fragmented thermite projectiles

Abstract

A high-velocity impact-ignition testing system was used to study the dynamic response of brittle thermite projectiles impacting an inert steel target at velocities of 850 and 1200 m/s. The projectiles included consolidated aluminum and bismuth trioxide that were launched by a propellant driven gun into a catch chamber equipped with high-speed imaging diagnostics. The projectiles passed through a break-screen at the entrance to the chamber and either fragmented upon penetrating the break-screen or remained intact prior to impacting the steel target. In all cases, the projectiles pulverized upon impact, and a reacting debris cloud spreads through the catch chamber. At lower impact velocities, the fragmented and intact projectiles produced similar flame spreading rates of 217–255 m/s. At higher impact velocities, the intact projectile produced the slowest average flame spreading rate of 179 m/s because debris rebounding was limited by the length of the projectile and the resulting debris field was highly consolidated in the radial direction. In contrast, the fragmented projectile rebounded into a well dispersed debris cloud with the highest, 353 m/s, flame spreading rate. A kinetic energy flux threshold was proposed as a means for describing the shift in observed debris dispersion and flame spreading rates. A reactivity model was developed based on particle burn times using a computational fluid dynamics code that incorporated heat transfer and particle combustion in a multiphase environment to understand how the particle size influenced flame spreading. Results from the model show a trade-off between faster reactivity and increased drag inhibiting movement for smaller particle debris.

Enhancement of thermal properties of Al/MoO3 thermite by electrostatic spraying

“…The thermite stands out due to its excellent combustion efficiency, high energy‐releasing rate, and high reaction exothermic enthalpy, which catches the attention of researchers. Thermite has been widely used in gas generator, 3 welding, 4 ammunition destruction 5 and high‐energy additives in propellants 6,7 …”

“…Thermite has been widely used in gas generator, 3 welding, 4 ammunition destruction 5 and high-energy additives in propellants. 6,7 The thermite composed of metal oxide and metal powder possesses unique chemical properties, which mainly is ascribed to the nature of its components. Typically, the thermite composed of Al and Fe 2 O 3 is used for railway welding.…”

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“…Thermite has attracted the attention of many researchers because of its high combustion efficiency, high energy release rate, and good reaction release enthalpy. Thermite is widely used in welding and gas generation [1][2][3], and it is a high-energy additive. Recently, nano thermite has attracted much attention owing to its large specific surface area and smaller particle spacing [4].…”