Publication

Bio-inspired Structures for Enhancing Energy Dissipation of Helmets

Mengbo Kang
2022
Projet étudiant
Résumé

The risk of concussion remains high in snow sports, even with a high helmet adoption rate. Novel helmet designs with enhanced energy dissipation are needed to solve this issue. In this study, helmet liners with bio-inspired honeycomb structures were proposed and fabricated with SLA 3D printing technology. The structures exhibited a distinct progressive folding behavior in the out-of-plane crushing tests. The buckling and plateau stress of bio-inspired honeycombs are higher than that of traditional ones. FEM models were developed in Abaqus to simulate the progressive folding behavior. The stress and strain curves obtained from the simulations match the test data to a great extent. Based on the simulations, the bio-inspired honeycombs can absorb the same amount of energy with a 24% weight reduction compared to EPS foams. Improvement is possible with smaller unit cells at the same equivalent density. Different material properties can influence the bucking and plateau stress of the structures differently. And with a multi-layer design, the honeycomb liners have the potential to suit a wide range of impact energy.

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Concepts associés (32)
Stress–strain curve
In engineering and materials science, a stress–strain curve for a material gives the relationship between stress and strain. It is obtained by gradually applying load to a test coupon and measuring the deformation, from which the stress and strain can be determined (see tensile testing). These curves reveal many of the properties of a material, such as the Young's modulus, the yield strength and the ultimate tensile strength. Generally speaking, curves representing the relationship between stress and strain in any form of deformation can be regarded as stress–strain curves.
Necking (engineering)
In engineering and materials science, necking is a mode of tensile deformation where relatively large amounts of strain localize disproportionately in a small region of the material. The resulting prominent decrease in local cross-sectional area provides the basis for the name "neck". Because the local strains in the neck are large, necking is often closely associated with yielding, a form of plastic deformation associated with ductile materials, often metals or polymers.
Finite strain theory
In continuum mechanics, the finite strain theory—also called large strain theory, or large deformation theory—deals with deformations in which strains and/or rotations are large enough to invalidate assumptions inherent in infinitesimal strain theory. In this case, the undeformed and deformed configurations of the continuum are significantly different, requiring a clear distinction between them. This is commonly the case with elastomers, plastically-deforming materials and other fluids and biological soft tissue.
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