A new auxetic structure with significantly reduced stress concentration effects

Abstract

Auxetic structures exhibit certain abnormal mechanical responses such as negative Poisson's ratios, mainly through the intertwined deformation attributes of inter-connected members of macro structural forms. Considering the relative ease of achieving complex forms with the advent of the additive manufacturing technologies, there is a renewed interest in auxetic structures, as the already established as well as new structural shapes are physically produced and tested to ascertain the theoretical predictions. While the focus was mostly around the auxetic responses, the stress distribution patterns and in particular the stress concentration effects were mostly neglected. This paper fills this gap, evaluating the stress concentration aspects of a standard re-entrant auxetic structure. A new structure is designed and proven to be less stressed in comparison with the re-entrant form commonly reported in the literature by means of analytical, experimental, and numerical results. The new structure proposed has proved to be more auxetic up to 15% of the external strain and with Poisson's ratios up to −2.5.