Dynamic compression-shear ignition mechanism of Al/PTFE reactive materials

Abstract

Ignition of Al/PTFE reactive materials can occur under dynamic loading. The ignition mechanism involves a mechanical-thermal-chemical coupled process, which draws the attention of scientists and engineers. However, it is difficult to understand the mechanism, especially under complex loadings. In this paper, three different shapes of Al/PTFE sample, 0° cylinder, 30° oblique cylinder and 45° oblique cylinder, were designed. The dynamic ignition tests were carried out by Split Hopkinson Pressure Bar (SHPB). The deformation, damage and fracture process were analyzed. The mechanical response depended on the shape of the sample, which determined the dynamic compression-shear states, further it induced different ignition behavior. The energy absorption rate ignition criterion was proposed to take the place of the traditional strain rate ignition criterion. The new criterion could match the testing well. In addition, numerical simulation on SHPB was conducted. It verified that Johnson-Cook model would describe the dynamic behavior of Al/PTFE reactive materials. The damage and the fracture of Al/PTFE under dynamic compression-shear loading was quantified well, and further was related to the ignition behavior observed during the tests. Finally, the dynamic compression-shear ignition mechanism of Al/PTFE reactive materials was revealed.