Examination of the Impact of Helmets on the Level of Transferred Loads to the Head Under Ballistic and Blast Loads

The main causes of human Traumatic Brain Injuries (TBIs) in war zones are ballistic impacts and blast waves. While understanding the mechanism of TBI and the brain injury thresholds are in urgent needs, efficiency of helmets as injury protective is not well-examined. To address these gaps, this study investigates the impact of ballistic helmets and padding systems on the biomechanical responses of the brain under dynamic ballistics and blasts loads. A nonlinear human head-neck finite element modeling procedure has been employed for the analysis. The results are examined against de-facto standard experimental data. The response of the finite element head model (FEHM) in terms of biomechanical parameters of the brain has been examined to measure the influence of padding system materials on the level of the loads transferred to the head. The results show when a bullet hits the front of the helmet vertically, the brain experiences the highest amount of stresses in comparisons with other impact orientations. Also, low stiffness foams cause less amount of load to be transferred to the head, indicating the importance of the mechanical properties of the padding system in helmet design. Parametric studies have also been carried out to examine the efficiency of the helmet under various blast situations and intensities by varying standoff distances and orientation angles of the FEHM. The results indicate that the protected heads experience lower accelerations, and stresses than unprotected heads. In general it was found that the performance of the helmet depends on the extent of the coverage of the head by helmet. To examine the influence of the entire human body in comparison with the only head model, the torso and attached to the head was modeled and the responses of the brain to equivalent loadings were examined. In general for the first few milliseconds of the assault on the head, biomechanical parameters of the brain remain independent of the torso. However, one can iv see the body influence as times goes by. As a conclusion one can rely on the results of the head and neck model to be credible enough for brain injury analysis