A novel bio-inspired helmet with auxetic lattice liners for mitigating traumatic brain injury

Abstract

The human head is most vulnerable to injury during activities such as road traffic and sports. To mitigate the risk of traumatic brain injury (TBI), helmets serve as an important protective device. This study proposes a hedgehog biomimetic helmet with auxetic lattice liners in the shape of a hemisphere. The helmeted head impact configuration is built based on a high bio-fidelity head-neck finite element model incorporated into our novel helmet model. Biomechanical responses including acceleration, intracranial pressure, and von Mises strain of head are extracted from the simulation model to assess TBI risks. The results indicate that the helmet featuring auxetic lattice liners outperforms those without liners or with other liner designs, offering superior protection. Compared to the threshold, the novel helmet design was found to reduce the head injury criterion value by 72.65%. Additionally, parametric studies of lattice’s bar radius for uniform and graded auxetic lattice liners are discussed. Finally, this study also carries out the optimization design of lattice strut radius and height, resulting in a lightweight auxetic lattice liner with superior protective performance. The outcomes of this study extend the application of auxetic materials and provide guidance for designing helmet liners that better mitigate TBI.

Auxetics and FEA: Modern Materials Driven by Modern Simulation Methods

“…In 2020, Airoldi et al [282] studied foam-filled energy absorbers with auxetic behaviour for localized impacts and compared the results of FEA simulation to experimental results. A more recent study by Chen et al (2023) employed FEA to investigate the effect of re-entrant arrowhead liners on helmet protection performance [283]. Through this study, it was illustrated that the auxetic lattice liners offer resistance to indentation, thereby enhancing the protection performance of the helmet [283].…”

“…A more recent study by Chen et al (2023) employed FEA to investigate the effect of re-entrant arrowhead liners on helmet protection performance [283]. Through this study, it was illustrated that the auxetic lattice liners offer resistance to indentation, thereby enhancing the protection performance of the helmet [283].…”

Focus on smart materials and structures for sporting protective equipment

“…The optimised structure outperformed conventional helmet foam during full-helmet simulations, demonstrating scalability of the optimisation process. Chen et al used the spines that protect hedgehogs as inspiration for a new mechanical metamaterial [8]. Hedgehog spines are thought to protect from impact, allowing them to evade predators by jumping from trees while rolled into a tight ball.…”

“…The focus issue highlighted the strong interest in smart materials for sporting impact protection. Noted challenges include adapting between the wide range of requirements; changing user groups, body types, and different types of impacts [2][3][4][5][6][7][8][9][10][11]. The impact or loading conditions and response that should be targeted when selecting or optimising effective smart material properties are developing with knowledge of injury risks [2][3][4]11].…”

“…Scaling smart-material manufacturing routes to achieve these, allowing transfer from laboratory to commercial products, is also noted as a challenge [2,7]. The collection of papers provides new routes to achieve these, including efficient optimisation [7] and fabrication methods [6,9], and new options for structures and smart systems to improve these [5,6,8].…”