Auxetic 3D rotating octahedra frameworks

Rotating unit metamaterials, as their name implies, are a class of auxetic systems which possess deformation mechanisms characterised by rotating blocks of material relative to one another. In this work, we propose a new class of hierarchical rotating unit systems made from octahedral frameworks connected to each other at the vertices. These systems, which are presented in terms of two distinct configurations: full-block and hierarchical ligament-based; were studied using a dual approach involving an extensive parametric finite element simulation run of various systems and experimental tests on prototype structures produced using stereolithography methods. These metamaterials have been shown to exhibit auxetic behaviour coupled with a high level of anisotropy, while other properties such as stiffness and volume fraction can also be tailored according to the necessary requirements. These properties make them ideal for potential applications in the fields of biomedical and aerospace engineering where lightweight systems with considerable stiffness and auxetic properties are often desirable.