Optimisation of an elastomeric pre-buckled honeycomb helmet liner for advanced impact mitigation

Abstract

Advances in computational modelling now offer an efficient route to developing novel helmet liners that could exceed contemporary materials' performance. Furthermore, the rise of accessible additive manufacturing presents a viable route to achieving otherwise unobtainable material structures. This study leverages an established finite element-based approach to the optimisation of cellular structures for the loading conditions of a typical helmet impact. A novel elastomeric pre-buckled honeycomb structure is adopted and optimised, the performance of which is baselined relative to vinyl nitrile foam under direct and oblique loading conditions. Results demonstrate that a simplified optimisation strategy is scalable to represent the behaviour of a full helmet. Under oblique impact conditions, the optimised pre-buckled honeycomb liner exceeds the contemporary material performance when considering computed kinematic metrics head and rotational injury criterion, by up to 49.9% and 56.6%. Furthermore, when considering tissue-based severity metrics via finite element simulations of a human brain model, maximum principal strain and cumulative strain density measures are reduced by 14.9% and 66.7% when comparing the new material, to baseline.

Focus on smart materials and structures for sporting protective equipment

“…Processes to tune the response of helmets are key to their continued development [2]. Adams et al demonstrate an efficient approach to parametrically optimise a pre-buckled honeycomb structure using a finite element approach [7]. Periodic boundary conditions applied to a two-by-two cell representative volume element approximated a continuous liner, and intracellular deformation gradients, allowing repeated simulations and optimisation.…”

“…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].…”

“…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].…”

“…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].…”