Comparative folding/unfolding performance of notch-type compliant joints

Origami design has been a popular research field for decades, generating inspiration for various structural applications. The shift from paper to more practical materials such as plate-like metals is materialized by surrogate folds such as compliant hinges. Therefore, it is critical to explore the kinematic and dynamic characteristics of these joints. In this paper, a comparative numerical study of the folding/unfolding performance of three notch-type compliant joints, namely groove, elliptical holes, and rectangular holes is presented. Indicators including stress contour, load-deformation, moment-angle, and stiffness-angle are selected to evaluate the performance of joints with different geometric parameters, especially the hysteretic behaviors of the joints. The results illustrate that the geometric parameters of the plate and joint are well correlated with these performance indicators. The transition behaviors of the folding/unfolding stiffness of all joints are associated with a certain regime of rotational angles. Besides, the performances of all studied joints are benchmarked against the much-popularized outside LET joint, from which their deformation modes are recognized. Finally, considering various performance aspects, the groove joint is recognized as the most suitable for the folding of a planar plate.