Modelling ballistic impact on military helmets: The relevance of projectile plasticity

The need to develop armour systems to protect against attacks from various sources is increasingly a matter of personal, social and national security. To develop innovative armour systems it is necessary to monitor developments being made on the type, technology and performance of the threats (weapons, projectiles, explosives, etc.) Specifically, the use of high protection level helmets on the battlefield is essential. The development of evaluation methods that can predict injuries and trauma is therefore of major importance. However, the risk of injuries or trauma that can arise from induced accelerations is an additional consideration. To develop new materials and layouts for helmets it is necessary to study the effects caused by ballistic impacts in the human head on various scenarios. The use of numerical simulation is a fundamental tool in this process. The work here presented focuses on the use of numerical simulation (finite elements analysis) to predict the consequences of bullet impacts on military helmets on human injuries. The main objectives are to assess the level and probability of head trauma using the Head Injury Criterion, caused by the impact of a 9 mm NATO projectile on a PASGT helmet and to quantify the relevance of projectile plasticity on the whole modelling process. The accelerations derived from the impact phenomenon and the deformations caused on the helmet are evaluated using fully three-dimensional models of the helmet, head, neck and projectile. Impact studies are done at impact angles ranging from 0 to 75 degrees. Results are presented and discussed in terms of HIC and probability of acceleration induced trauma levels. Thorough comparison analyses are done using a rigid and a deformable projectile and it is observed that plastic deformation of the projectile is a significant energy dissipation mechanism in the whole impact process. (C) 2020 China Ordnance Society. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd.