Thermomechanical deformation of polyethylene-terephthalate artificial muscles

Polymer-based artificial structures have attracted great interest due to their potential applications in space systems, flexible electronics, and soft robots. In this work, we investigate the creep deformation of polymer-based artificial muscles, which are made from polyethylene-terephthalate (PET) fibers of 0.25 and 0.48 mm in diameter, respectively, in a temperature range of 80–110 °C. The creep deformation of the PET-artificial muscles consists of linearly elastic deformation and viscoelastic deformation. A nonlinear Burger's model is used to analyze the viscoelastic deformation of the PET-artificial muscles. Increasing temperature decreases the shear moduli of the elastic components in the nonlinear Burger's model. The viscosities of the nonlinear viscous elements in the nonlinear Burger's model decrease with the increase of the creep temperature and are dependent on the training load used in constructing the PET-artificial muscles. The PET-artificial muscles exhibit stress softening. The nominal activation energies are linearly decreasing functions of the training load.