Local Actuation of Elastic Origami

Origami and engineering are two concepts which do not traditionally have much in common; however, recently more and more interest has been payed to origami structures by engineers. Put simply engineering origami is an engineering structure that employs folds. This could be in deployable structures at a range of sizes, or alternatively, in morphing structures where origami allows engineers to go from a flat sheet to a 3D object. To practically achieve these in real engineering systems the origami structures would have to be embedded with actuators to control the shape, providing localised actuations. The most basic understanding of how these origami structures behave assumes that the material between the folds, known as a facet, is infinitely stiff and the folds are perfect hinges. This can be used to show that a pattern called the Miura-ori, a unit cell that can be tessellated into a larger structure, has a single degree of freedom. This means that an actuation anywhere will propagate evenly to the entire structure. However, in the real world the folds are not perfect hinges and the facets are not infinitely rigid, instead both have finite stiffnesses. This means that there are more degrees of freedom, and a localised actuation would decay instead of propagating evenly. It is this decay that is the focus of this project, as it is one of the limiting factors determining where the actuators must be placed in an origami system to achieve the desired deformations. To simplify the problem Miura-ori tubes have been chosen to investigate this decay, because everything happens in just one direction along the length of the tube. ABAQUS simulations are verified using experimental data, however, they also allow for the removal of things like gravity or manufacturing imperfections which can influence the results of an experiment. ABAQUS is then used to tune the stiffness of the facets and folds and investigate how that influences how a localised actuation propagates. This can be used to give a better understanding of the behaviour of local actuation in origami structures.