(In)efficacy of architected auxetic materials for impact mitigation

It has been demonstrated that auxetic materials, characterized by a negative Poisson’s ratio, offer enhanced resistance to indentation, shear forces, fracture toughness and the absorption of energy. As such, they are reported in literature to be promising options for impact mitigation in military and space contexts. Auxetic materials are rare in nature, and must therefore be designed and manufactured artificially in order to be applied. Densification of auxetic materials in order to absorb impact energy in a limited area has been the focus in the literature to date. However, this results in a concentration of the force paths, which is not desirable for impact mitigation. In this work, the effects of auxetic densification on the stress distribution over the backside of the auxetic material are addressed using both experimental and simulative trials. In this study, the distinction between auxetic and conventional honeycombs in force transmission characteristics is examined. This is achieved through an analysis of experimental data and the utilization of numerical techniques to enhance comprehension of the internal mechanisms of architected materials in response to impact. • Experimental and numerical high-velocity impact studies conducted. • Auxetic lattices densify underneath the impact, thus localizing the forces. • Energy absorption alone is not a sufficient measure for impact mitigation. • Conventional honeycombs are able to spread the load both in time and in space.