Feasibility of optimising bicycle helmet design safety through the use of additive manufactured TPE cellular structures

Bicycle helmets are designed to attenuate forces and accelerations experienced by the head during cycling accidents. An essential element of bicycle helmet design is, therefore, the appropriate manufacturing of energy-dissipating components. The focus of this study was to evaluate the feasibility of using thermoplastic elastomer (TPE) cellular structures (Duraform® Flex), manufactured via a laser sintering (LS) process, as the energy-dissipating inner liner of the bicycle helmet. This study is presented in two sections; the optimisation of the LS process capabilities for the manufacture of cellular structures and an evaluation of the effects of cellular structure density on helmet impact kinematics. Through the fabrication and testing of tensile and compressive specimens, each process parameter (laser power, scanning exposure, build temperature and part orientation) was optimised to maximise compressive strength. The energy-dissipating characteristics of helmet cellular structures, made from this optimised material, were evaluated during simulated helmeted headform impact tests. Reduced accelerations and increased pulse durations were reported for decreased structural densities, demonstrating improved energy-dissipating characteristics for this novel technique. This study demonstrates that cellular structure-based inner liners, manufactured via additive manufacturing processes, have exciting potential towards improving bicycle helmet safety.

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