Modeling memory effects in amorphous polymers

A model that can describe the shape memory behavior of amorphous polymers based on theory of multiple natural configurations is presented and implemented for use in applications. The thermodynamic framework presented considers evolution of multiple natural configurations and models the key features, especially, the temperature and deformation dependent change in stiffness and shape memorizing characteristics. A single parameter called the degree of glass transition is used to describe the memory locking and releasing characteristics. Using this framework and specialization to small deformations, the developed model is implemented in ABAQUS through VUMAT subroutine feature and correlated with existing epoxy shape memory experiments. Various thermomechanical conditions on structural components such as rods under tension and compression and beams are analyzed. Simulations results confirm that the model is capable of predicting the memory characteristics including the multi-shape memory locking and release mechanisms.