Formulation and numerical implementation of tensile shape memory process of shape memory polymers

Formulations and numerical simulations of shape memory process are essential issues in mechanical characterizations of shape memory polymers (SMPs). In this study, tensile stress and strain in the typical four-step thermal shape memory process are formulated basing on a Neo-Hookean hyper-viscoelastic constitutive equation that could consider the time-temperature effect, where the stress evolution equations that could consider the coupling of hyperelastic and viscous properties are derived and applied to calibrate the hyper-viscoelastic material parameters of an epoxy SMP. The numerical simulation method of shape memory process is established by coding the Arrhenius equation and utilizing the commonly used 3D Neo-Hookean hyper-viscoelastic model in ABAQUS. To verify the numerical method, finite element simulations are performed to predict the shape memory experiments with different strains in free and constrained recovery modes. As a result, the maximum relative deviation of 6.3% between the numerical predictions and the experimental results indicates the reasonability of the numerical method. (C) 2018 Elsevier Ltd. All rights reserved.