Energy Release and Fragmentation of Brittle Aluminum Reactive Material Cases

Abstract

Cylindrical reactive material cases produced by the consolidation of an aluminum powder were tested via explosive launch in a closed chamber. One configuration measured the quasistatic overpressure generated by the case and explosive, and two further tests focused on soft‐catch of fragments before and after striking the chamber walls. On a volumetric basis, the reactive material cases produced two to three times the combustion energy of an aluminum 6061 alloy case or a bare nitromethane explosive that was tested as comparisons. The metal combustion primarily occurs after case fragments impact the walls. Increasing the reactive material case thickness produces a higher pressure but lower combustion efficiency per unit mass, despite producing comparable or slightly more fine fragments on a per gram basis. Though the brittle, pressed aluminum cases have low toughness and tensile strength, recovered fragment patterns show a range of fragment sizes up to 1 mm, with approximately one‐third of the mass below 100 μm.

Enhancement of explosive effect of thermobaric explosive by metal reactive material

“…The reactive materials with Zr or Al as reaction elements release energy through exothermic reaction under highspeed impact and explosion loads [1][2][3][4][5][6][7][8][9][10]. The reaction conditions and energy release characteristics of the reactive materials have been extensively studied [11][12][13][14][15].…”

“…F. Zhang et al [6] believed that microscopic hot spots were generated in the reactive material under explosion load, which promoted the material to break into fine fragments, made the reaction occur within sub-millisecond time, and enhanced the explosion shock wave. J. C. Kline et al [7] found that the use of MRMC can greatly increase the total combustion energy, and thicker casing will lead to insufficient material energy release. The report of N. Du et al [8] also confirmed this phenomenon and found that the thinning of MRMC under explosion is conducive to the increase of far-field air shock wave.…”

“…J. C. Kline et al. [7] found that the use of MRMC can greatly increase the total combustion energy, and thicker casing will lead to insufficient material energy release. The report of N. Du et al.…”

In situ measurement of the fragmentation behavior of Al/PTFE reactive materials subjected to explosive loading, Part 1: Fragment size measurements

“…For high velocity impact conditions, strain rates between 10 3 s À 1 and 10 4 s À 1 can be expected and 10 4 s À 1 is typical for explosive events. Fragments produced from the dynamic failure of an RM system under these conditions are fragile, and typically collected using soft catch systems with low density catch mediums [2][3][4][5][6][7][8]. The use of a low density catch medium permits the fragments to be caught while mitigating additional fracture of the fragments [4].…”

“…Early soft catch systems utilized shaving cream as the catch medium [2], while current systems utilize artificial snow [3,4,[6][7][8]. The use of artificial snow simplifies the fragment extraction process, as the snow is simply melted, and water filtered to recover the fragments.…”