Modeling and simulation of structurally dynamic crystallizable shape memory polymers with light-induced bond exchange reaction

Shape Memory polymers (SMPs) is a novel class of smart polymeric materials that have been attracted tremendous scientific interest within the last decades. SMPs have the ability to "remember" their original shape even after undergoing significant deformation into a temporary shape. For most first generation of SMPs, the shape memory effect was accomplished by a thermally induced process, triggered in many different ways, such as heating/cooling, electromagnetic field and infrared light. The transient shape in thermally induced SMPs is due to a glassy phase or a semi-crystalline phase. The thermally induced SMPs which temporary shape is fixed through crystallization is called crystallizable shape memory polymers (CSMPs). For traditional CSMPs, their original shape is predefined and is not able to be reprogrammed. This limits the applications of the CSMPs. Recently, a new class of CSMPs has been developed. These materials can perform a typical thermally induced shape memory cycle, but their original shape can be reprogrammed through exposing to UV light. The shape reprogramming effect is governed by light induced covalent bonds exchange reaction, while the shape memory effect-As typical CSMPs-is due to solid-phase crystallization. In this work, we focus on modeling the mechanical behavior of this new class of structurally dynamic CSMPs. The framework used in developing the model is built upon the theory of multiple natural configurations[1]. The model has been applied to solve a specific boundary condition problem, namely uni-Axial tension. Furthermore, we implement our model through Abaqus (commercial finite element package) subroutine UMAT to simulate 3D behavior of this attractive material.