Abstract
Elastic neutral stability in compliant mechanisms is a remarkable appearance since it requires the energetic state of the structure to remain unchanged during a deformation mode. Several examples in literature require either plastic deformation or external constraints to be enforced to obtain a state of pre-stress and often require the use of anisotropic materials. This paper presents a new type of compliant shell structure featuring a neutrally stable deformation mode without requiring one of the aforementioned conditions. The shell structure is composed of two initially flat compliant facets that are connected via a curved crease. The structure can be reconfigured into a second zero-energy state via propagation of a transition region, without any apparent effort. Both the structure’s local width and local crease curvature can be tuned to reach neutral stability during transition. The modelled results are verified by several prototypes that match the modelled predictions qualitatively, as well as by measurement results that show quantitative agreement. The new type of structure introduced here features neutral stability without relying on the application of pre-stress during manufacturing or externally applied boundary conditions. Moreover, it shows potential for combining geometric simplicity with complex and highly tune-able behaviour.
Highlights
A surprisingly simple yet intriguing structure arises when two flat arched-shaped compliant sheets are stacked and connected in a hinged fashion along their shortest curved edges
The structure can arguably be classified as a compliant facet origami mechanism (COFOM), an origami mechanism wherein compliance of the facets is used to incorporate energy storage [2]
The method section of this paper addresses the approach taken to investigate the behaviour during transition, as well as the influence of two design parameters hereon
Summary
A surprisingly simple yet intriguing structure arises when two flat arched-shaped compliant sheets are stacked and connected in a hinged fashion along their shortest curved edges. Transition between the stable states is not straightforward since the curved nature of the hinge does not allow energyfree operation. This type of hinge can be considered a curved crease and, the structure can be classified as curvedcrease origami. The structure can arguably be classified as a compliant facet origami mechanism (COFOM), an origami mechanism wherein compliance of the facets is used to incorporate energy storage [2]
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