The optimisation of flexible impact-protection systems for varying strain rates and energies.

Abstract

The need for smarter and active, energy absorbing systems designed especially for human protection applications has sparked interest in highly strain rate sensitive compounds. This thesis describes the iterative design, development and optimisation of a novel form of energy absorbing, body worn protection. The original contribution to knowledge is the development of a novel strain rate sensitive protection system incorporating synergetic internal architecture. Co-continuous blends of silicone based dilatant and thermoplastic elastomer have been developed through a recursive design process to develop a new material specifically optimised for body worn protection. Failure mechanisms were analysed, and from these results techniques have been developed to mitigate internal fracture mechanisms. This enabled the development of a strain rate sensitive material utilised with an internal architecture. The novel material properties were examined and developed using monolithic samples, tested at a variety of energies, speed and environmental conditions. Methods for designing and developing auxetic structures that work synergistically with the new material have been developed. The novel system has also been combined with textiles, and the merit of this combination explored. An improvement in performance has been validated, as well as a design improvement through being able to attach parts directly to garments. The resulting impact protectors are applicable over a range of strain rates. Systems have been designed to incorporate this novel technology in pre-production prototypes in three selected market areas, which typify low, medium and high impact speeds. The work also explores the systems ability to manage multiple impacts at the same location with a surprisingly low loss in performance, effectively making a protector that can withstand repeat impacts. This work has contributed to the methods previously used in testing personal protective equipment. The techniques developed in this work have enabled new revision of these PPE standards, as well as directly contributing to two new standards.