A Modified Constitutive Model for Shape Memory Polymers Based on Nonlinear Thermo-Visco-Hyperelasticity with Application to Multi-Physics Problems

Abstract

Shape memory polymers (SMPs) as a class of smart material have provided diverse attributes recently used in different applications. Raising the usage of SMPs, especially in more sensitive environments, such as the human body or similar high-risk circumstances, highlights the necessity of more accurate simulations. Suitable constitutive modeling is the foundation of an accurate simulation. Not only should such modeling consider precise details to diminish errors, but also it must provide a robust and powerful procedure to calibrate the material parameters. To achieve these goals, in this paper a modified constitutive model for SMPs based on the concept of internal state variables and rational thermodynamics is proposed in large deformation. Taking its basis from the nonlinear hyperelasticity and viscoelasticity, the model can provide a more accurate prediction of SMPs response. In comparison to other available constitutive models based on viscoelastic approach, the number of material parameters is smaller. Furthermore, performing a new approach for material parameters extraction, two different SMP materials were calibrated. The proposed model’s capability was assessed by comparing the model outputs with experimental results in diverse conditions such as different temperature rates and applied stretch ratios. The user-friendly implementation process of this model in multi-physics software based on the finite element method can be counted as another advantage of the proposed model. Hence, to simulate smart systems containing SMP elements, three multi-physics analyses in various fields and conditions were performed, and the importance of conducting such multi-physics phenomena has been discussed.