Design and Optimization of a Shape Memory Alloy Based Self Folding Sheet

Abstract

Origami engineering—the practice of creating useful threedimensional structures through folding and foldlike operations on twodimensional buildingblocks—has the potential to impact several areas of design and manufacturing. In this article, we study a new concept for a selffolding system. It consists of an active, selfmorphing laminate that includes two meshes of thermallyactuated shape memory alloy (SMA) wire separated by a compliant passive layer. The goal of this article is to analyze the folding behavior and examine key engineering tradeoffs associated with the proposed system. We consider the impact of several design variables including mesh wire thickness, mesh wire spacing, thickness of the insulating elastomer layer, and heating power. Response parameters of interest include effective folding angle, maximum von Mises stress in the SMA, maximum temperature in the SMA, maximum temperature in the elastomer, and radius of curvature at the fold line. We identify an optimized physical realization for maximizing folding capability under mechanical and thermal failure constraints. Furthermore, we conclude that the proposed selffolding system is capable of achieving folds of significant magnitude (as measured by the effective folding angle) as required to create useful 3D structures.