School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 021383, USA.
Proc Natl Acad Sci U S A. 2012 Apr 17;109(16):5978-83. doi: 10.1073/pnas.1115674109. Epub 2012 Mar 26.
We introduce a class of continuum shell structures, the Buckliball, which undergoes a structural transformation induced by buckling under pressure loading. The geometry of the Buckliball comprises a spherical shell patterned with a regular array of circular voids. In order for the pattern transformation to be induced by buckling, the possible number and arrangement of these voids are found to be restricted to five specific configurations. Below a critical internal pressure, the narrow ligaments between the voids buckle, leading to a cooperative buckling cascade of the skeleton of the ball. This ligament buckling leads to closure of the voids and a reduction of the total volume of the shell by up to 54%, while remaining spherical, thereby opening the possibility of encapsulation. We use a combination of precision desktop-scale experiments, finite element simulations, and scaling analyses to explore the underlying mechanics of these foldable structures, finding excellent qualitative and quantitative agreement. Given that this folding mechanism is induced by a mechanical instability, our Buckliball opens the possibility for reversible encapsulation, over a wide range of length scales.
我们引入了一类连续体壳结构，即 Buckliball，它在受压载荷下发生屈曲诱导的结构转变。Buckliball 的几何形状由一个具有规则圆形空隙排列的球形壳组成。为了使图案变形是由屈曲引起的，这些空隙的可能数量和排列被发现受到五种特定构型的限制。在临界内压以下，空隙之间的狭窄韧带发生屈曲，导致球的骨架发生协同屈曲级联。这种韧带屈曲导致空隙的闭合和壳的总体积减少多达 54%，同时保持球形，从而为封装开辟了可能性。我们使用精密台式实验、有限元模拟和标度分析的组合来探索这些可折叠结构的潜在力学，发现了极好的定性和定量一致性。由于这种折叠机制是由机械不稳定性引起的，我们的 Buckliball 为在广泛的长度尺度上进行可逆封装开辟了可能性。
