3D phase-evolution-based thermomechanical constitutive model of shape memory polymer with finite element implementation

Shape memory polymers (SMPs) are a class of smart materials which can undergo transition between two different states (temporary shape and permanent state) induced by external stimuli, such as temperature, light etc. In order to study the deformation behavior of this fast-developing SMP structures, the key points are formulating suitable theoretical constitutive models to correctly reflect the material behavior and developing appropriate numerical simulation techniques to handle complex structures. In this paper, we proposed a three-dimensional (3D) thermomechanical constitutive model of SMPs and its implementation as a user material subroutine, UMAT, in a finite element package ABAQUS. The shape memory effects of the SMPs under three different loading patterns are simulated by the proposed approach and the acquired numerical results are compared with theoretical computational results and available experimental data. They agree reasonably well. Two SMP structural examples are presented to demonstrate the feasibility of the proposed approach. The exercises involve the analyses of (i) an intelligent hexachiral deployable structure and (ii) a 3D self-folding structure achieved through a 2D plate.