Inherently Disordered Auxetic Metamaterials

Inherently disordered auxetic systems represent a new class of metamaterial structures, which have the capability of exhibiting advanced functionalities despite the absence of global symmetry and ordered localized periodicity. In this work, disordered frameworks based on the Delaunay-triangulation network incorporating chiral honeycomb features are proposed. These systems show large auxetic behavior, which is retained irrespective of the extent of disorder and depends entirely on the degree of chiralization. Furthermore, the Young's modulus of these systems can be controlled as a function of seed density, similar to how volume fraction determines stiffness in foams, without altering the auxeticity of these systems. Finally, the wide-ranging parametric finite element study and experimental tests carried out in this work, revealed that the disordered topology of these systems significantly alters the failure pathways and deformation propagation profile of these metamaterials with respect to their ordered counterparts. The findings of this work clearly demonstrate that advanced functionalities such as auxeticity are not exclusive only to ordered frameworks and that, by harnessing disorder, one may potentially obtain additional superior properties, which are not present in traditional metamaterials.