Failure analysis of auxetic lattice structures under crush load

Lattice structures are promising materials in the terms of energy absorption, acoustic and vibrational damping, high strength-to-weight ratios and thermal management capabilities. In particular, auxetic lattice structures, among others, show high energy absorption performances due to their characteristic negative Poisson's ratio. In this study, it is aimed to compare auxetic deformation mechanisms under quasi-static crush loads. Ti6Al4V tensile test specimens were produced with Electron Beam Melting (EBM) Additive Manufacturing (AM) technology. Moreover, a constitutive equation was derived and calibrated according to tensile results. The calibrated data were used to generate non-linear computational crush models including elastoplastic material data, damage initiation criterion, damage evaluation law and element deletion. The computational models are utilized for optimum topology design and mechanical performance prediction of different auxetic cells, including anti-tetrachiral, hexachiral, re-entrant and honeycomb lattice structures that are prone to prematurely fail under crush loading conditions. Consequently, it was found that the chiral auxetic deformation mechanism experienced better energy absorption ability over re-entrant deformation mechanism for metallic lattice structures.