Use of low-density, reticulated, elastomeric foam impregnated with Newtonian and non-Newtonian fluids to design an impact absorption material

Abstract

The development of new threats in recent conflicts, such as improvised explosive devices (IEDs), requires the development of improved protection for US soldiers. The development of improved materials for helmets, in particular, is motivated by the social and economic costs of head injury. A versatile liner, adaptable to different types of helmets, with different constraints, would be useful. In this thesis, we first review the statistics related to head injuries from motor vehicle and recreational accidents and then describe the state of the art of current helmet design. An experimental study of the response of a widely used helmet liner material (polystyrene foam) and a new potential liner material (low-density, reticulated, elastomeric foam impregnated with Newtonian and non-Newtonian fluids) under impact shows some complementarities and leads to the concept of a composite material that would take advantage of the properties of the two materials. To conduct an extensive design analysis, comprehensive models are developed to model the behavior of each material under a wide range of impact energies. A complete model for the composite bilayer of the two materials is then compared to experimental data; the model gives a good description of the data. Using these results, three case studies are developed for a motorcycle helmet, a football helmet and a military helmet. The three case studies show a variety of constraints in term of thickness of the liner and impacting energies. Simulations are conducted using the models developed to indentify potential designs that would meet the requirement in term of peak linear acceleration (PLA) and in term of the specific constraints of each type of helmet. Finally, in an experimental study, some of the proposed designs are tested for repeated loading. The proposed designs enhance the level of protection in term of peak linear acceleration and show promising behavior under repeated impact testing.