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Developing novel materials to enhance motorcyclist safety

Robinson, Michael 2019. Developing novel materials to enhance motorcyclist safety. PhD Thesis, Cardiff University.
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Abstract

The number of motorcyclists in Wales has reached record highs and, while accounting for only 0.7% of the vehicles in Wales, they accounted for ~35% of the injuries categorised as killed or seriously injured. Most studies in the literature have shown that the use of motorcycle helmets reduces the probability of brain injury and death, with strong support for their use from international bodies such as the world health organisation. This work aimed to improve motorcyclist head protection by augmenting the single impact performance of existing helmets with multi-impact mitigation. The following objectives supported this aim: An approach to improve elastomeric Fused Filament Fabrication (FFF) manufacturing quality was developed, and an equivalent porosity to injection moulding components was demonstrated. A novel accessible approach, using a uniaxial test machine to characterise elastomers dynamically, was developed. A novel computational method to generate elastomeric rate-dependent energy absorption diagrams was also developed. Additionally, the ability to scale these diagrams between different base elastomers was demonstrated. After selecting a preliminary configuration from an energy absorption diagram, a subsequent simplified simulation of a motorcycle helmet impact enabled efficient optimisation. This approach was successfully used to predict the response of a more complex helmet assembly. A similar agreement between simulation and experimental work was observed for this approach, as was observed when simulating a fully modelled helmet assembly. A prototype helmet, containing an elastomeric cellular structure, was shown to repeatedly pass the requirements of UNECE 22.05 while demonstrating a consistent co-efficient of restitution equivalent to that of an expanded polystyrene (EPS) helmet, even as shell failure occurred. The prototype helmet met the requirements of UNECE 22.05 at three of the four investigated locations. Additionally, it exceeded EPS' performance at one location with a liner thickness of 70% that of EPS.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: Additive Manufacturing; Dynamic; Impact; Elastomer; Motorcycle Helmet; Cellular Structure.
Date of First Compliant Deposit: 1 October 2020
Last Modified: 02 Oct 2020 15:32
URI: https://orca.cardiff.ac.uk/id/eprint/135228

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