Assessment of Non-Lethal Projectile Head Impacts

Anti-personnel Non-Lethal Weapons (NLW) are used to impart sufficient effect onto a person in order to deter uncivil, suspect or hazardous behaviour with a low prob- ability of permanent or fatal injury. They appear to be suitable for many law enforcement missions and to a certain extent to the military forces. In fact, in many situations of conflict, where the army and civil police 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 de- formable or breakable projectile with masses between 5 g to 140 g at initial velocities between 70 m/s and 160 m/s. Practically, KENLW are not used without risk for the targeted persons. The head zone represents the most critical part of the human body regarding non-lethal projectile impacts. The inflicted injuries can be severe and sometimes lead to death. The experts in the field should identify the limits in which KENLW should be effective without causing permanent or fatal injuries. Therefore, assessment methods should be developed in order to predict the injury risk of non-lethal head impacts. The present thesis proposes the development of three different approaches allowing the assessment of the non-lethal head impacts. The first approach named FW (Force wall) method has been developed at DGA (Direction Générale de l’Armement) - France. For a benchmark projectile, this method links the maximum impact head force to the maximum impact force mea- sured on a supposedly infinitely rigid structure, equipped with a piezoelectric force sensor. Three lesional thresholds: unconsciousness, meningeal damage and bone damage with coma are used. The FW method proposes the extension of the bench- mark projectile results to other projectiles using the assumption: two different pro- jectiles producing the same force on a rigid structure, will have the same effects on the head. This method is applied in the present thesis for different projectiles using a specific experimental setup. Different improvements have been achieved regarding the frequency analysis of the rigid structure and the quantification of uncertainties of the FW method. These improvements represent some original contributions of the present thesis.The second approach concerns the use of a mechanical surrogate in order to predict the maximum impact head force. The mechanical surrogate involved in the present study is BLSH (Ballistics Load Sensing Headform). Different tests have been performed using no less than eight commercial projectiles. The third approach uses numerical simulations with a validated FEHM (Fi- nite Element Head Model). SUFEHM (Strasbourg University Finite Element Head Model) is considered in the present thesis. The model offers the possibility to pre- dict head injuries using other parameters than the maximum impact head force: the strain energy and the Von Mises stress. A specific method is proposed in order to develop the FE (Finite Element) models of non-lethal projectiles. Six FE models of projectiles are used for the numerical simulations. Results show a good agreement between the three methods for the benchmark projectile. The extension of the FW method for other projectiles can be performed with some limitations mentioned in the present document. Moreover, there is a good agreement between BLSH and SUFEHM for all studied projectiles. Different correlations between the maximum impact head force and other criteria are also proposed in order to include them in the non-lethal head impact injury prediction. Ultimately, the present work proposes assessment methods for non-lethal projec- tile head impacts. The different details of these methods are given in the present document