Design and analysis of 2D double-U auxetic honeycombs

Abstract

Abstract In this study, two dimensional double-U auxetic honeycombs (2D DUHs) composed of curved shell members have been proposed based on traditional double-V (concave quadrilateral or re-entrant double-arrowhead) auxetic honeycombs (2D DVHs). Theoretical analysis, numerical simulation and compression experiments are adopted to characterize the mechanical properties including equivalent Young's modulus, equivalent Poisson's ratio, and quasi-static collapse process of 2D DVHs and DUHs. Specimens of the 2D DUHs and DVHs made of Aluminum alloy (A6061) are fabricated through wire cut electrical discharge machining. Both numerical and experimental results illustrate that concave DUHs exhibit tunable negative Poisson's ratio and equivalent stiffness level compared to DVHs. Furthermore, DUHs have smooth geometry configurations that can reduce stress concentration at elastic region and exhibit stronger auxetic behavior during large deformation. Those mechanical properties of 2D DUHs satisfy the requirements for practical engineering applications such as energy absorption. The dynamic crushing responses of 2D DVHs and DUHs are also investigated, and it is found that the crushing collapse modes and plateau stress improvement of 2D DUHs are related to the crushing velocity. Finally, the local impact responses of 2D DVHs and DUHs are studied numerically, the influences of impact velocity and indenter size are considered. This study provides useful instructions for the design, fabrication and analysis of auxetic structures, which has a broad prospect in some advanced technical applications.