Easy snap-folding of hexagonal ring origami by geometric modifications
Easy snap-folding of hexagonal ring origami by geometric modifications
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DOI：
10.1016/j.jmps.2022.105142
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发表时间：
2022-11
影响因子：
5.3
通讯作者：
Lu Lu-Lu;Sophie Leanza;Jize Dai;Xiaohao Sun;R. Zhao
中科院分区：
文献类型：
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作者：
Lu Lu-Lu;Sophie Leanza;Jize Dai;Xiaohao Sun;R. Zhao
六角环折纸是一种可折叠结构，具有令人印象深刻的包装能力，可以镶嵌成二维或三维表面，没有任何间隙或重叠。它可以在弯曲或扭转载荷下折叠成桃核形状的结构，其面积仅为其初始面积的 10.6%。然而，在大型可折叠结构的应用中，通过弯曲或扭转进行折叠通常在技术上是困难的。在这里，我们提出了通过简单的点载荷或局部扭转或挤压来促进六角环轻松折叠的策略。这是通过对六角环进行的两项几何修改来实现的：引入残余应变和创建预扭曲边缘。通过结合理论建模、有限元模拟和实验，我们系统地研究了具有残余应变和预扭曲边缘的改进六边形环的折弯行为。研究发现，几何修改通过不同的机制促进六边形环轻松折叠：引入残余应变可以显着降低能量势垒，从而减少折叠环所需的力矩，同时创建预扭曲边缘可以轻松实现面外变形，这是环折叠的必要条件。结合这两种方法进一步能够通过点载荷或局部扭转或挤压来折叠六角形环。为了演示改良环的大型组件的轻松折叠，我们构建了各种结构，通过在环的角部进行简单压缩，可以将其从最初的三维状态折叠到体积显着降低的最终状态。我们预计，所提出的几何修改策略可以为合理设计具有极高包装率的基于易于折叠的环形折纸的可折叠功能结构提供新的视角。
Hexagonal ring origami is a type of foldable structure that has impressive packing abilities and can be tessellated into two-dimensional or three-dimensional surfaces without any gap or overlap. It can be folded under bending or twisting loads into a peach core-shaped configuration with only 10.6% of its initial area. However, in applications of large-scale foldable structures, folding by bending or twisting is usually technically difficult. Here, we propose strategies to facilitate easy snap-folding of the hexagonal ring by a simple point load or localized twist or squeeze. This is enabled by two geometric modifications made to the hexagonal ring: introducing residual strain and creating pre-twisted edges. By combining theoretical modeling, finite element simulations, and experiments, we systematically investigate the snap-folding behaviors of modified hexagonal rings with residual strain and pre-twisted edges. It is found that the geometric modifications promote easy snap-folding of the hexagonal ring by different mechanisms: introducing residual strain can significantly decrease the energy barrier and thus reduce the required moment to snap-fold the ring, while creating pre-twisted edges allows for easy out-of-plane deformation which is a necessary condition for a ring to fold. Combining the two methods further enables the snap-folding of the hexagonal ring by a point load or localized twist or squeeze. To demonstrate the easy folding of large assemblies of the modified rings, we construct various structures that can be snap-folded from their initial three-dimensional states to significantly lower-volume final states by a simple compression at the corners of the rings. We envision that the proposed geometric modification strategies can provide a new perspective on the rational design of easy-to-fold ring origami-based foldable functional structures with extremely high packing ratios.