A 3D auxetic material based on intersecting double arrowheads

Recent years have seen a consistent trend in the extension of 2D auxetic models towards 3D ones. This article introduces a 3D auxetic linkage structure by extending the double arrowhead honeycomb structure to an intersecting double arrowhead structure. A geometrical analysis on the basis of rigid linkages with rotational joints shows that auxeticity is manifested in all three orthogonal planes. Results reveal that the geometry, in terms of either the relative linkage lengths or the half angles, can be changed to substantially control the Poisson's ratio. It is herein suggested that functionally graded beams and plates that exhibit gradual change in Poisson's ratio from negative to positive, as well as functionally graded solids with opposing auxeticity trends on different planes, are easily achievable by 3D printing using the intersecting double arrowhead structure, and that further mechanistic analysis be performed.