Impact-Initiation Sensitivity of High-Temperature PTFE-Al-W Reactive Materials

Tao Sun,Yuanfeng Zheng,Haifu Wang,Ying Yuan

doi:10.3390/cryst12010030

Abstract

Drop-weight tests were conducted to investigate the impact-initiation sensitivity of high-temperature PTFE-Al-W reactive materials. The test results show that the impact-initiation sensitivity of the materials more than doubles with increasing the sample temperature from 25 to 350 °C. Combined with the impact-induced initiation process recorded by high-speed video and the difference between reacted and unreacted residues, the crack-induced initiation mechanism was revealed. The rapid propagation of crack provides a high-temperature and aerobic environment where Al reacts violently to PTFE, which induces the initiation. Moreover, the influence of sample temperature on the sensitivity was discussed and analyzed. The analysis results indicate that the sensitivity shows a temperature interval effect, and 127 and 327 °C are the interval boundaries where the sensitivity changes significantly. The sensitivity may leaps at 127 °C and increases more rapidly in the temperature interval from 127 to 327 °C, but hardly changes after the temperature reaches 327 °C.

Highlights

Reactive materials are classified as a kind of energetic structural materials
Many studies on formulations and fabrications [3], mechanical properties [4], impact initiation [5], and energy release characteristics [6] have been conducted based on theoretical analysis, numerical simulation, and experiments
Ge [16] obtained an opposite conclusion, where the impact-initiation sensitivity increased with the increased W content, for brittle PTFE-Al-W reactive materials fabricated under a much lower sintering temperature and a much shorter duration

Summary

Introduction

Reactive materials are classified as a kind of energetic structural materials. Such material stays inert and insensitive under ambient conditions but reacts violently with a large amount of chemical energy released upon dynamic loading. Ge [16] obtained an opposite conclusion, where the impact-initiation sensitivity increased with the increased W content, for brittle PTFE-Al-W reactive materials fabricated under a much lower sintering temperature and a much shorter duration. Xu [18] conducted a series of ballistic experiments to investigate the influence of impact velocity on the energy release characteristics of a PTFE-Al-W reactive material projectile. A series of drop-weight tests were conducted to study the impact-initiation sensitivities of high-temperature PTFE/Al/W reactive materials. The well-known “up-and down” test method [20] was adopted in this study to obtain the characteristic drop height which can be expressed as: The impact sensitivity of the materials was characterized by a characteristic drop height, at which the material had a 50% probability of reaction. Where Ec is the impact energy to initiate, M is the drop mass, g is the acceleration of gravity, and vc is the impact velocity

Crack-Induced Initiation Mechanism

Influence of Temperature on Impact Sensitivity

Thermal Sensitivity

Conclusions