The Role of Porosity and Annealing on the Dynamic Mechanical Properties of an Aluminum Reactive Mate

CDR Ming-ling (Leo) Shen, Taiwan Navy

Abstract: Thermobaric warhead designs now commonly use a reactive fragment liner, in which brittle metal composites are launched off the warhead and provide additional lethality via aerobic metal combustion. Currently there is no systematic understanding of how the physical properties of a reactive material such as a pressed aluminum (Al) can be optimized for lethality. The fragmentation under impact or explosive launch is an especially important but poorly understood property. Here we fabricate a series of reactive materials using gas-atomized Al H-2 powders. Samples are compacted in a cold isostatic press at 60 ksi and 30 ksi, followed by annealing at 200 °C for up to 30 minutes. The resulting dynamic strength is evaluated by Split-Hopkinson Pressure Bar testing and impact fragmentation is studied using sabot-launch from a 0.5” gas gun. Fragments of each sample are collected in an artificial snow medium and analyzed with a computerized particle analyzer and scanning electron microscope. The results allow us to observe trends with porosity and dislocation density; both strongly influence fragmentation but have a smaller effect on strength. Fragment distributions are well described by a variant of the traditional Mott distribution.

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Jul 05, 2017

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