On-demand tuning of mechanical stiffness and stability of Kresling origami harnessing its nonrigid folding characteristics

Abstract

Being adaptive with respect to changing operating conditions and the environment are imperative demands for advanced engineering structures. In this research, two Kresling origami units are stacked together to form an online and on-demand tunable Dual-Kresling Origami Structure (D-KOS), allowing easy and significant change of the multistability profile and apparent stiffness without redesign. Specifically, by harnessing its non-rigid folding nature together with geometric characteristics, D-KOS can be programmed to follow distinct paths of its strain energy contour as varying ϕp (rotational angle of the top plate of the D-KOS), which can be utilized to explicitly derive different mechanical properties. The D-KOS with identical Kresling origami units can exhibit various symmetric bistable behaviors with different energy barrier via adjusting ϕp. Such a structure becomes a monostable system as the tuning variable reaches a critical value. This change of the energy landscape and stability profile gives rise to the change of stiffness at its stable equilibria, which as a result creates a wide range of stiffness value one can achieve, including quasi-zero stiffness. Such tuning of ϕp does not require redesign of the structure, and thus can achieve online and on-demand tailoring. To verify the concept, proof-of-concept prototypes are developed and utilized to validate the D-KOS’s mechanical tunability experimentally. Moreover, different design parameters of D-KOS can change the tunability of D-KOS. For example, the D-KOS with non-identical Kresling origami units can possess even richer stability properties (being asymmetric bistable, symmetric bistable and monostable) with various energy landscapes. In addition, one can also tailor the range of the adjustable stiffness by changing the design parameters, such as ratio of the angle between polygon side and valley crease of the triangular facets, and the height of Kresling origami unit.