Connectivity of Shape Memory Alloy-based Self-Folding Structures

Structures inspired by origami have attractive characteristics such as the potential to be reconfigurable, reduced manufacturing complexity, and the capability to be folded into compact forms for storage. In some circumstances, it may be impractical to apply external manipulations to generate the desired folds in origami-inspired structures (e.g., as in remote applications such as deployable satellite members, solar arrays, etc.). In such cases, self-folding capabilities may be necessary. The self-folding system considered herein consists of a laminate with outer layers of thermally actuated shape memory alloy (SMA) separated by a compliant and insulating layer. Localized actuation of the SMA layers allows for control of the laminate curvature anywhere in the sheet, allowing the initially planar sheet to reconfigure into a 3D structure. For self-folding structures created with this laminate, it is inefficient to hold permanent heating at the actuated regions to maintain the shape of the folded structure. Connectivity systems are proposed to avoid such permanent heating. Different ideas for connectivity systems are studied in this work via finite element analysis (FEA). The connections are compared in different aspects such as the capability of maintaining the folded structure upon cooling, the capability of disconnecting after connection is achieved, the complexity of the maneuver needed to connect the structure, and the complexity of adding multiple connections in a sheet for any general complex structure.