Stiffening multi-stable origami tubes by outward popping of creases

Abstract

In this letter, we study the tunable stiffness and the multi-stability of corrugated tubes consisting of serially interconnected hexagonal frusta based on the Kresling origami pattern. Depending on the appropriate geometric designs, the corrugated origami tube either has straw-like behavior with an axial inversion and bending multi-stability, or has multiple axial stable states via a twisting motion. We focus on the latter category and reveal another stable “pop-up” configuration via outward popping of the valley creases. By switching among the three types of stable configurations, the corrugated tube can exhibit drastically different axial and bending stiffness. Moreover, the deformation mode can switch from twisting to inversion after the pop-up. To quantify the tunable mechanical properties, we employ an elasticity-based bar and hinge model and perform parametric studies that give insight on the relationships between geometry and mechanics. The results suggest that designs with a higher initial twisting angle and a lower initial slope will provide more significant stiffness and shape tuning, and that for specific designs the frustum stiffness can be increased by four orders of magnitude after pop-up. To validate the numerical results, we fabricate proof-of-concept origami frusta and corrugated tubes. These prototypes demonstrate the desired multi-stable behavior, the tunable stiffness, and mode switching deformations. These corrugated origami tubes have potential applications including mechanical devices of tunable properties, deployable structures, reconfigurable robotic components, and more.