Impact sensitivity of intermetallic nanocomposites: A study on compositional and bulk density

High density intermetallic nanocomposites are being considered as a replacement for kinetic energy projectiles in ordnance applications. These composites release a large amount of chemical energy upon penetration and provide an enhanced blast effect on the target; in comparison to inert projectiles. A fundamental understanding of the response to mechanical initiation as a function of the composite’s compositional and bulk density are presented for aluminum-based intermetallics. Composites ranged in compositional density from 3.5 to 17.9 g/cc and included Al-Ti, Al-Ni, Al-W, Al-Hf, Al-Zn pressed to bulk densities that ranged from 50 to 80% of the theoretical maximum. Aluminum particle size was also investigated and ranged from nanometer to micron-scale spherical diameters. Ignition was stimulated via a modified type 12 impact tester used to measure the sensitivity of the composite to drop weight impact. The tests were recorded using high-speed thermal imaging to ensure a positive reaction. Results show that the nano Al particle composites are more sensitive to impact ignition than their micron scale counterparts. As bulk density increases, the samples become increasingly sensitive to ignition and display an average 70% decrease in ignition energy. Compositional density also plays a critical role in ignition energy. As the density of the composite increases, regardless of the Al particle size, the composites become more sensitive to ignition. Results show that at the same bulk density, higher compositional density composites such as Al-W require 80% less ignition energy than lower compositional density composites such as Al-Ti (1.01 cm compared with 0.34 cm, respectively).