Numerical simulation for behind armor blunt trauma of human torso under non-penetrating ballistic impact

A human torso finite element model with high bio-fidelity was developed to study the behind armor blunt trauma (BABT) of pistol cartridge on human torso with bulletproof composite structure (BCS) and the effect of buffer layer (expandable polyethylene, EPE) on BABT. The bulletproof structure was made of multilayered composite of aluminum alloy (AlSi10Mg) and thermoplastic polyurethanes (TPU), and the ANSYS/LS-DYNA software was used to simulate the blunt ballistic impact process of pistol cartridge on human torso. Results indicated that the BCS could resist the shooting speed of 515 m/s without being broken. During the process of pistol cartridge shooting the BCS, the energy of pistol cartridge was transmitted to the human organs through the BCS, thereby causing human injury. Moreover, the mechanical response parameters of various organs were determined by the distance between the human organs and the impact point. The sternal fracture and liver rupture were not produced based on the threshold stress of sternum and liver injury, no matter whether the buffer layer was added or not. According to the Axelsson injury model, a slight to moderate injury was created when there was no buffer layer, but the injury level was trace to slight caused by the buffer layer with thickness of 1.0 mm, and the buffer layer with thickness of 2.5 mm and 5.0 mm caused subtle BABT. It was concluded that the buffer layer could effectively reduce the BABT, and the reduction was related to the thickness of the buffer layer. This study reveals the mechanism of the BABT, which can provide a theoretical basis for the design of the bulletproof structure and the evaluation of structural bulletproof performance and protection performance.