Ballistic helmets: Recent advances in materials, protection mechanisms, performance, and head injury mitigation

Combat helmets provide protection against ballistic threats and blunt impact forces, and wearing them has greatly reduced head injuries and saved lives of many soldiers. With the new challenges from improvised explosive devices and urban combat operations in modern asymmetric military conflicts, future combat helmets are required to be highly protective, lightweight, comfortable to wear, and compatible with communication and other systems. The aim of this paper is to provide a comprehensive review of existing combat helmets based on aramid and UHMWPE fibers by addressing the critical issues including materials, ballistic impact mechanisms, design, manufacturing, performance, and head injury protection. Various ballistic fabrics and composites used for combat helmets are discussed. The ballistic impact mechanisms and mechanical responses of helmet composites are examined in view of experimental methods, analytical models, and numerical simulations. The strategies for helmet designs, including head coverage and curvature of helmet shell, manufacturing processes, and liner foam pads, are outlined. The performance of combat helmets as evaluated by ballistic testing and finite element simulations is summarized. Finally, the ballistic and blast impact induced head injuries are elaborated, and the possibility of behind armor blunt trauma predicted by available injury criteria is discussed. The state-of-the-art knowledge of combat helmets reviewed in this paper provides the foundation for the development of next-generation combat helmets, which are expected to protect against ballistic, blunt, and blast impacts to minimize traumatic brain injuries, while enabling wearing comfort and effective communications.