Abstract
Auxetic materials exhibiting a negative Poisson’s ratio are of great research interest due to their unusual mechanical responses and a wide range of potential deployment. Efforts have been devoted to exploring novel 2D and 3D auxetic structures through rational design, optimization, and taking inspiration from nature. Here we report a 3D architected lattice system showing a negative Poisson’s ratio over a wide range of applied uniaxial stretch. 3D printing, experimental tests, numerical simulation, and analytical modeling are implemented to quantify the evolution of the Poisson’s ratio and reveal the underlying mechanisms responsible for this unusual behavior. We further show that the auxetic behavior can be controlled by tailoring the geometric features of the ligaments. The findings reported here provide a new routine to design architected metamaterial systems exhibiting unusual properties and having a wide range of potential applications.
Highlights
Cellular structures are widely spread in natural systems, such as wood, human bone, and beaks of birds[1, 2]
Auxetic systems consisting of networks of buckliball[56], chiral-like structures[57], orthotropic laminated open-cell frameworks[58] have been fabricated via 3D printing and very recently, a metallic 3D auxetic cellular structure consisting of cubic chiral unit cells has been fabricated via selective electron beam melting[59]
When the applied strain is higher than 0.32, some beams start to break, leading to the drops in the stress-strain curves. These structures exhibit J-shaped stress-strain curves, which are very similar to the mechanical response of the lattice materials previously reported[55]
Summary
Cellular structures are widely spread in natural systems, such as wood, human bone, and beaks of birds[1, 2]. Auxetic systems consisting of networks of buckliball[56], chiral-like structures[57], orthotropic laminated open-cell frameworks[58] have been fabricated via 3D printing and very recently, a metallic 3D auxetic cellular structure consisting of cubic chiral unit cells has been fabricated via selective electron beam melting[59] In all of these systems, the auxetic behavior is exhibited only in the limit of small strains, and the design of 3D auxetic systems capable of obtaining these unusual properties at large strains still remains a challenge[60, 61]. We report an architected lattice material system that exhibits tunable negative Poisson’s ratio over a wide range of applied uniaxial stretch, which is intrinsically governed by the out-of-plane deformation in the curved ligaments. We will demonstrate our design concept through integrative numerical simulation, analytical modeling, 3D printing, and experimental tests
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