Design Tools for Patterned Self-Folding Reconfigurable Structures Based on Programmable Active Laminates

Abstract

Engineering inspired by origami has the potential to impact several areas in the development of morphing structures and mechanisms. Self-folding capabilities in particular are necessary in situations when it may be impractical to exert external manipulations to produce the desired folds (e.g., as in remote applications such as in space systems). In this work, origami principles are utilized to allow planar sheets to self-fold into complex structures along arbitrary folds (i.e., no hinges or pre-engineered locations of folding). The sheets considered herein are composed of shape memory alloy (SMA)-based laminated composites. SMAs are materials that can change their shape by thermal and/or mechanical stimuli. The generation of sheets that can be folded into the desired structures is done using origami design software such as Tachi's freeform origami. Also, a novel in-house fold pattern design software capable of generating straight and curved fold patterns has been developed. The in-house software generates creased and uncreased fold patterns and converts them into finite element meshes that can be analyzed in finite element analysis (FEA) software considering the thermomechanically coupled constitutive response of the SMA material. Finite element simulations are performed to determine whether by appropriately heating the planar unfolded sheet it is possible to fold it into the desired structure. The results show that a wide range of self-folding structures can be folded via thermal stimulus. This is demonstrated by analyzing the folding response of multiple designs generated from freeform origami and the newly developed in-house origami design software.