Novel hybrid auxetic structures for improved in- plane mechanical properties via additive manufacturing

Auxetic metamaterials have evolved growing beyond the cellular material structures and offering unique combinations of both auxetic and mechanical properties. However, the understanding and development of these promising material structures have been predominantly based on analytical evaluation methods, as practical implementation was restricted by manufacturing limitations. The manufacturing limitation has changed quite significantly with the advent of additive manufacturing methods, particularly with direct metal printing, such as selective laser melting. Ever since, the auxetic meta material structures began attracting renewed interests, and several different new structural forms and hybridisation of certain existing models followed, focussing specifically on enhancing auxeticity as well as other mechanical attributes. A recently developed and novel S-shaped unit cell based auxetic structure is hybridised with star re-entrant unit cells and analysed both numerically and experimentally based on physical forms produced by selective laser melting as part of the research reported here. Numerical and experimental results correlated sufficiently, depitcing significant enhanced auxeticity as high as −3, and mechanical property with the hybrid structures.