Evaluation of protective performance of children helmets via biomechanical modelling.

<i>Purpose</i>: The purpose of the current study was to compare the protective performance of helmet designs with different sizes and cushion materials for skull and brain injuries in children. <i>Methods</i>: A 6-year-old child head finite element (FE) model with high biofidelity was used to conduct impact simulations under the protection of helmets with different sizes (small, medium and large) and cushion materials (EPS-expanded polystyrene, PU-polyurethane and airbag) according to the testing conditions specified by the standard. Then, the protective performance of different helmet designs was evaluated by assessing skull and brain injury risk calculated based on the kinematic and biomechanical response of the child head model. <i>Results</i>: The skull fracture risk of children under the protection of airbag helmets is lower than that of EPS and PU helmets by more than 50%. Large-sized helmets, with thicker padding, show better protective capability for skull injury compared to small-sized helmets. The risk of brain injury under airbag helmet protection is significantly lower than EPS and PU helmet under 4.8 m/s sharp anvil impact test condition, and small sized helmet could generally reduce brain injury risk under the 6.2 m/s flat anvil impact test condition. However, no obvious effect has been found of helmet size and material to brain injury risk in the impact scenarios at 6.2 m/s. <i>Conclusions</i>: The size and cushion material of the helmet have a significant influence on its skull injury protection performance, but their effect pattern on brain injury protection capability is not obvious. The use of airbag helmets with larger buffering stroke can effectively reduce both the risk of skull and brain injuries under relatively low impact loads.