Development of lightweight composite helmet using auxetic materials

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The use of military helmets has greatly reduced injuries and saved lives of many soldiers. A helmet's protective capabilities are evaluated on the basis of two primary test measures: resistance to penetration (RTP) and back face deformation (BFD). Many factors are considered during ballistic helmet design, including comfort, weight, fit, and maintainability. Especially, being light in weight for military helmets is very important due to long-term operations. The ubiquitous use of lightweight composite materials in protective structures has created a formidable challenge in ensuring the same level of protectiveness as their metallic counterpart. Different approaches toward the development of more efficient materials have led to an interest in auxetic structures. Auxetic refers to a negative Poisson's ratio which is a meta-material property. Consequently, when a compressive load is applied to an auxetic, the material will contract in the direction orthogonal to the applied load, creating a denser region. This densification makes auxetics suited to severe loading conditions such as impact. This research programme will examine their effectiveness in the design of lightweight composite helmets.In order to decrease design cycle times and ensure that safe design standards are met, virtual tests are usually performed by numerical simulation. The virtual impact test data are subsequently used as part of the development of a new design. These numerical simulations produce results without building a physical model, and can be performed relatively quickly and inexpensively. This permits optimization of the design before an actual prototype of the helmet has to be built.The aim of this project is to develop an optimum composite helmet using auxetic core structure, to deliver the lightest possible military helmet with improved ballistic efficiency. A new finite element model will be developed to analyse the impact response of composite sandwich panels using auxetic cores. The effect of helmet shell material, shell thickness, impact velocities, and impact types (with hemispherical and flat anvils) on the performance will also be studied. "