Modeling and Design of Shape Memory Alloy-based Origami Structures with Smooth Folds
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2017, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. Engineering inspired by origami has the potential to impact the development of morphing structures. Active material-based origami structures with self-folding capabilities are particularly needed in cases where it may be impractical to apply mechanical loads to exert the desired folding deformation (as in remote applications such as in aerospace systems). Current models and design methods for origami are generally limited to the idealization of the folds as creases of zeroth-order geometric continuity. For origami structures with significant fold thickness or folded via active material actuation, such a representation is not accurate. In such cases, the folds are properly represented through bent regions with higher-order geometric continuity. These fold regions of higher-order geometric continuity are termed as smooth folds. A method for the design of a single planar sheet and its associated pattern of smooth folds that morphs via active material actuation towards a given three-dimensional goal shape is presented here. Shape memory alloy (SMA) origami structures are specifically considered. The SMA regions in the origami structures are assumed to be in an initially pre-strained martensite phase. For actuation-driven folding deformation, the temperature is uniformly increased in the structure until all the SMA regions fully complete phase transformation from pre-strained martensite to austenite. The width of the folds is designed considering the allowable bending deformation provided by the SMA-actuated smooth folds. The theory and implementation of such a design method and the structural analysis approach used to simulate origami structures folded via SMA actuation are presented. The results show that every determined origami structure design matches its associated goal shape in a known folded configuration under the prescribed boundary conditions. The proposed method can be utilized for the design of origami morphing structures having SMA actuation and can be applied for structures morphed using other active materials.