Numerical Prediction of the Yield Surface of a Chiral Auxetic Structure

For today's requirements, the material itself is often not sufficient anymore. This leads to structural cellular materials and metamaterials, which allow for more degrees of freedom by a strong structure-property relationship. Auxetic structures investigated in this contribution belong to metamaterials. Auxetic metamaterials show huge advantages in their properties, e.g., an enhanced specific energy absorption capacity (SEAC) as well as a negative Poisson's ratio, combined with a very high stiffness-to-weight ratio. Experimental probing of these structures is very challenging, hence, up to now, auxetic materials have only been investigated in uniaxial, bending, or shear loading. But for an industrial application, the knowledge of the multiaxial yield behavior is inevitable. For the first time, the present study deals with the numerical probing of the yield surface for a chiral auxetic structure applying multiaxial loading. The changes in Poisson's ratio, SEAC, and the resulting nonconvex yield surface are studied numerically. It shows that the highest specific energy absorption capacities are reached under compression load cases while higher stiffnesses and yield stresses are achieved under tensile loading. There is a strong structure-property relationship and load case dependency for Poisson's ratio as well as for the SEAC. Numerical probing of the yield surface for a chiral auxetic structure applying multiaxial loading is performed. Further, the change in Poisson's ratio as well as the specific energy absorption capacity is investigated. It shows that the highest specific energy absorption capacities are reached under compression load cases while higher stiffnesses and yield stresses are achieved under tensile loading.image (c) 2023 WILEY-VCH GmbH