Improving the Deformability and Recovery Moment of Shape Memory Polymer Composites for Bending Actuators: Multiple Neutral Axis Skins and Deployable Core

Abstract

Shape memory polymer composite (SMPC) actuators havereceived significantattention for applications in space deployable structures becauseof their light weight and simple actuating process without any additionalcomponents. However, conventional SMPC actuators exhibit limited deformationowing to damages caused by the slight elongation of fibers and microbuckling.In this study, we designed a sandwich-structured SMPC bending actuatorto increase deformability and the recovery moment with two novel features:multiple neutral axis (MNA) skins and a deployable core. The MNA skinswere fabricated as layered structures of a soft layer (the polydimethylsiloxane/ethoxylatedpolyethylenimine layer) and hard layers (the SMPC layer) based onthe MNA effect derived from the large modulus difference between thesoft and hard layers. Under the bending deformation, the large shearstrain in the soft layer significantly decreases the axial strainin SMPC layers and increases deformability. Applying the deployablecore on the sandwich-structured SMPC bending actuator increases therecovery moment owing to the deploying force of the core. To the bestof our knowledge, the sandwich-structured SMPC bending actuator composedof two MNA skins and a deployable core yielded the world'slargest width-normalized recovery moment of 51.2 N & BULL;m/m with thesmallest bending radius of 15 mm.