Assessment of Non Lethal Projectile Head Impacts
Anti personnel NLW (Non Lethal Weapons) are used to impart sufficient effect onto a person in order to deter uncivil, suspect or hazardous behaviour with a low probability of permanent or fatal injury. In many situations of conflict, where the army and law enforcement units are involved, the use of such weapons can ensure a minimal risk of collateral damage. The most used NLW are Kinetic Energy Non Lethal Weapons (KENLW) that involve the shooting of a deformable or breakable projectile. Since their first use, real cases indicate that the injuries inflicted by such projectiles may be irreversible and sometimes lead to death, especially for the head impacts. Therefore, there is a necessity to assess the head impacts in order to allow a safer use of such projectiles. This article concludes a 4 year study where three methods, independently developed, are considered to be applicable for the head risk assessment. The first method links force measurements on rigid wall structure with cadaveric and animal impact test results. Lesional thresholds, in terms of the maximum impact force and intracranial pressure, are proposed for unconsciousness, meningeal damages and bone damages, respectively. The second one is based on direct impact force measurements on a specific mechanical surrogate. The third method makes use of numerical simulations using a validated finite element head model. The numerical model allows the prediction of different kind of injuries. Firstly, the necessity of the assessment of the non lethal head impacts is highlighted through some examples taken from literature. Secondly, the three different methods are detailed and illustrated for different projectiles. Outstanding results are given and a comparison between the different methods is proposed including some correlations between different criteria. Finally, some discussions and remarks conclude the present article.