High-Velocity Impacts of Pyrophoric Alloy Fragments on Thin Armour Steel Plates

The terminal ballistics effects of Intermetallic Reactive Materials (IRM) fragments have been the object of intense research in recent years. IRM fragments flying at velocities up to 2000 m/s represent a realistic threat in modern warfare scenarios as these materials are substituting conventional solutions in defense applications. The IRM add Impact Induced Energy Release (IIER) to the mechanical interaction with a target. Therefore, the necessity of investigations on IIER to quantify potential threats to existing protection systems. In this study, Mixed Rare Earths (MRE) fragments were used due to the mechanical and pyrophoric affinity with IRM, the commercial availability and cost-effectiveness. High-Velocity Impacts (HVI) of MRE were performed at velocities ranging from 800 to 1600 m/s and recorded using a high-speed camera. 70 MREs cylindrical fragments and 24 steel fragments were shot on armour steel plates with thicknesses ranging from 2 mm to 3 mm. The influence of the impact pitch angle (alpha) on HVI outcomes was assessed, defining a threshold value at alpha of 20 degrees. The influence of the failure modes of MRE and steel fragments on the critical impact velocities (CIV) and critical kinetic energy (E-kin crit) was evaluated. An energy-based model was developed and fitted with sufficient accuracy the Normalised E-Kin crit ((E) over tilde (crit)(kin)) determined from the experiments. IIER was observed in all the experiments involving MRE. From the analyses, it was observed that the IIER spreads behind the targets with velocities comparable to the residual velocities of plugs and shattered fragment.

Automated summary

The study investigated the terminal ballistics effects of intermetallic reactive materials fragments by performing high-velocity impact tests of mixed rare earth fragments on armor steel plates at various speeds. An energy-based model was developed and experiments showed that impact induced energy release was observed in all experiments involving mixed rare earth fragments.