Numerical simulation of non lethal projectiles on human thorax

These last decades have seen the development of a new type of weapons, the non lethal weapons. Unlike the conventional weapons which may cause severe or fatal injuries and whose injury mechanisms are well documented, the non lethal weapons are designed for temporary incapacitation with reversible consequences or minor damage to the human body. They try therefore to fill the gap wherever the use of excessive forces or conventional weapons is not necessary. There are various non lethal technologies but here we will focus on non lethal kinetic energy weapons (NLKEW).
The non penetrating characteristics of non lethal projectiles lead to different injury mechanisms to those related to conventional lethal projectiles. In order to better understand these effects and assess the injury severity, experiments are carried out on Post Mortem Human Surrogates (PMHS), animals and mechanical anthropomorphic systems. Nevertheless nowadays with the development of high performance computing systems, numerical simulations based on finite element method are increasingly used because of their cost-effectiveness, their predictive capabilities and their adaptability (for example the possibility of adapting the geometry to take into account various morphologies, …).
Physical injury is a consequence of the interaction between the human body and the projectile. To assess the severity of injury, injury criteria are defined. The most used criterion on the assessment of the thorax injury is the maximum viscous criterion. Because of the human body complexity, reliable information on injury mechanisms and tolerance level to the impact of non lethal projectiles is limited. The major challenge in the numerical simulations is the human tissue material model as human tissue responses to impacts are various and complex. As a consequence, models which are biofidelic to the human living tissues are a key issue.
To investigate and predict the human thorax response to the impact of the usual non lethal kinetic projectiles (like the FN303, the 40mm COUGAR), a finite element thorax model has been developed from thorax CT-scan images and the projectile FN303 was used. The model was validated by using results (force-time and deflection-time characteristics of the thorax) from experiments on PHMS published in the litterature. Two types of projectiles made of polyvinyl chloride cylinder with 37 mm diameter and respectively 28.5 mm and 100 mm long were used and the human tissue material models were found in open litterature.