Experimental and numerical study on the protective mechanism of the full helmet subjected to blast loadings

The efficacy of full helmets in ballistic protection is well established. However, their effectiveness against blasts remains uncertain. The study combines free-field blast tests and numerical simulations to comprehensively investigate the protective mechanism of the full helmet under blast shock waves. Four blast tests are conducted on a hybrid III dummy head model with various helmet configurations. Simultaneously, finite element (FE) models are developed to explore full helmet protection. Five blast scenarios are simulated, including bare head, helmet-head, helmet-mandible guard-head, helmet-visor-head, and full helmet models. The experimental results indicate that wearing the full protective helmet can effectively mitigate overpressure at the eyes and forehead, and the sealing of the helmet significantly affects the attenuation of the peak overpressure. The simulation results reveal that the full helmet can dramatically attenuate the head overpressure in the frontal blast but cause localized overpressure amplification due to the underwash effect. Meanwhile, shock wave propagation heavily relies on the gap between the head and foam pads. The effect of blast loading directions and helmet-mandible guard gap on the head overpressure are investigated. The findings indicate that the mandible guard and visor can cause localized overpressure amplification. The overpressure on the eyes and forehead regions has a linear relationship with the gap between the helmet and mandible guard.