Department of Mechanical Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
Sci Rep. 2017 Jan 4;7:39816. doi: 10.1038/srep39816.
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.
各向异性材料在活组织内形成，并广泛应用于工程结构中，在这些应用中，复杂的结构和功能设计原则对于使用这些材料至关重要。本文提出了一种候选的层压开孔泡沫框架，它是一种各向异性材料，具有显著的机械性能。通过增材制造，利用肘节梁和柱构件制成的各向同性微结构的层压来制造人工框架；这种制造的结构在三维空间中具有正交各向异性。单轴加载试验揭示了在面外方向上的强负泊松比（高负泊松比），在非线性弹性区域内可重复保持，且在拉伸和压缩加载下相等。有限元模拟支持周期性框架中单元的观察到的负泊松比行为，保留了正交固体的理论弹性特性。这些发现为基于几何形状的概念材料设计开辟了可能性。
