Orthotropic Laminated Open-cell Frameworks Retaining Strong Auxeticity under Large Uniaxial Loading

Abstract

Anisotropic materials form inside living tissue and are widely applied in engineered structures, where sophisticated structural and functional design principles are essential to employing these materials. This paper presents a candidate laminated open-cell framework, which is an anisotropic material that shows remarkable mechanical performance. Using additive manufacturing, artificial frameworks are fabricated by lamination of in-plane orthotropic microstructures made of elbowed beam and column members; this fabricated structure features orthogonal anisotropy in three-dimensional space. Uniaxial loading tests reveal strong auxeticity (high negative Poisson’s ratios) in the out-of-plane direction, which is retained reproducibly up to the nonlinear elastic region, and is equal under tensile and compressive loading. Finite element simulations support the observed auxetic behaviors for a unit cell in the periodic framework, which preserve the theoretical elastic properties of an orthogonal solid. These findings open the possibility of conceptual materials design based on geometry.

Transition mechanism for a periodic bar-and-joint framework with limited degrees of freedom controlled by uniaxial load and internal stiffness

“…The topic appears in a wide range of fields from geometry to crystallography to engineering, and indeed the mechanical behaviours of many of these structures remain unexplored. Some examples of such behaviours include auxeticity in materials of negative Poisson’s ratio [ 4 – 9 ], origami-based folding and deployment [ 10 – 14 ], and deformability of hierarchically arranged structures [ 15 – 17 ], in addition to the fundamental mechanical properties of rigidity and flexibility [ 18 – 22 ].…”

“…The topic appears in a wide range of fields from geometry to crystallography to engineering, and indeed the mechanical behaviours of many of these structures remain unexplored. Some examples of such behaviours include auxeticity in materials of negative Poisson's ratio [4][5][6][7][8][9], origami-based folding and deployment [10][11][12][13][14], and deformability 2018 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited.…”

Auxetic vibration behaviours of periodic tetrahedral units with a shared edge

“…Various repetitive structures composed of simple geometric shapes have been investigated extensively with the endeavour to enhance fundamental properties such as rigidity and flexibility [1][2][3][4]. While many rigid microstructures based on trusses have been developed from a mechanical viewpoint [5,6], flexible microstructures are expected to realize anomalous mechanical characteristics in solid matter, being distinctive in having, for example, non-positive values of Poisson's ratio [7][8][9][10][11] or coefficient of thermal expansion [12][13][14].…”

Numerical and Experimental Studies on the Deformation of Missing‐Rib and Mixed Structures under Compression

“…The deformation of porous materials under a compression load is more complex than simple uniaxial tension loading. The deformation of different auxetic structures under compression has been increasingly studied, such as negative Poisson's convex–concave foams, re‐entrant unit cell, disordered auxetic metamaterials, cellular frameworks, arrowhead structures, and missing‐rib (MR) auxetic structures . Yang et al studied the behavior of auxetic structures under compression using both static model and dynamic finite‐element (FE) modeling.…”