A crack-induced initiation mechanism of Al-PTFE under quasi-static compression and the investigation of influencing factors

Generally, the Al-PTFE is thought to be inert under quasi-static or static loads. However, it was recently found that after a specific heat treatment procedure AI-PTFE specimens could initiate under quasi-static compression. Sintering temperature, equivalence ratio and Al particle size were identified as three influencing factors of the initiation and were separately investigated by quasi-static compression tests, and reaction phenomena as well as stress-strain curves were recorded. Selected specimens were characterized by a scanning electron microscope (SEM). The results show that the sintering temperature controls the crystallinity of PTFE matrix, and the reactivity and toughness increase with the decreasing of crystallinity. The equivalence ratio affects the initiation as well as the propagation of reaction. Excessive Al particles would damage the continuity of the PTFE matrix, causing the decreasing of mechanical strength and reactivity. With the decreasing of Al particle size, the reactivity and toughness of Al-PTFE increase accordingly. A critical particle size exists between 3 mu m and 14 mu m, only below which the AI-PTFE could be initiated readily under quasi-static compression. A crack-induced initiation mechanism was proposed and was supported by SEM micrographs. (C) 2016 Elsevier Ltd. All rights reserved.