Design Study for Multifunctional 3D Re-entrant Auxetics

The increasing demands of safety, cost reduction, or weight reduction on components call for new, multifunctional materials. Mechanical metamaterials, such as auxetic materials, provide enhanced properties due to a specially tailored microstructure. The negative Poisson's ratio of auxetics, for instance, increases the impact and thermal shock resistance. Herein, a parametrized model of a modified auxetic structure is simulated using the finite-element software ABAQUS. Three out of five geometry parameters are varied between a minimum and maximum value to establish their impact on the energy absorption capacity and the Poisson's ratio using design of experiment (DoE). All eight resulting structures are additively manufactured by selective laser melting (SLM) and experimentally investigated under uniaxial compression to validate the simulations. The size of a unit cell has the biggest impact on both target values. Energy absorption capacity and Poisson's ratio are directly competing in optimization; hence, a compromise is necessary. The quasistatic compression experiments verify the simulation results up to the first collapse. Afterward, the specimens are brittle, which is not accounted for in the simulations, and this may result from the high process complexity of SLM manufacturing.