Effect of titanium fiber content on mechanical behaviors and explosive properties of Al/PTFE-RDX composite charges

To improve the mechanical behaviors and explosion performance of the Al/PTFE reactive materials, short-cut titanium fibers were added to Al/PTFE annular reactive materials, and subsequently assembled with RDX explosive column to form a composite charge. The effects of different titanium fiber contents on the mechanical behaviors of the annular reactive materials were investigated using a universal material testing machine and a split Hopkinson pressure bar. The influence of short-cut titanium fiber contents on the quasi-static pressure, shock wave parameters and thermal damage effects of the composite charge was studied in depth by the free-field explosion test system and spherical explosion container test system combined with the colorimetric temperature measurement technology. The temperature field of explosion flame was reconstructed by the colorimetric temperature measurement method with a high-speed camera, which was based on the gray-body radiation theory. A tungsten lamp calibrated the measurement accuracy of the temperature mapping system, and the fitting relationship between the temperatures and the gray values of the high-speed images was derived to obtain the conversion coefficient. The test results of mechanical properties showed that with the increase of titanium fiber content, the elastic modulus, yield strength and compressive strength of Al/PTFE annular reactive materials under quasi-static compression, as well as the yield strength and compressive strength under high-speed impact, all exhibited an initial increase, which were followed by a decrease, reaching the maximum values at 3% content. The experimental results of explosion performance showed that short-cut titanium fibers could significantly enhance the explosion performance of Al/PTFE-RDX composite charges. When the content of short-cut titanium fibers was 3%, the peak overpressure of the explosion shock wave, its positive phase duration and positive impulse were 37.68 kPa, 695.34 µs and 12.34 Pa·s, respectively. With 5% content of short-cut titanium fibers, the afterburning effect was the most significant. The maximum values of the explosion quasi-static pressure, average fireball temperature and fireball duration reached 70.50 kPa, 2782 K and 1668.90 µs, respectively. Analysis of solid explosion products indicated that short-cut titanium fibers could enhance the mechanical strength of the Al/PTFE matrix, delay the fragmentation time of the Al/PTFE annular reactive materials, promote the interfacial reactions, and participate in high-temperature chemical reactions, generating a synergistic effect and positive feedback to improve the mechanical toughness and energy release efficiency of the reactive materials.