Modeling the Mechanics of Multi-Stimuli Multi-Shape Memory Polymers

Abstract: Shape memory polymers have the ability to retain multiple temporary shapes, which can be reverted back to the original shape, or to another temporary shape, through the use of a suitable trigger. The most common stimuli used are temperature changes, exposure to light, and other activation mechanisms. These temporary shapes can be very complex and varied, involving large deformations. Because shape memory polymers are finding use in a wide variety of important applications ranging from aerospace and biomedical devices to sensors and actuators, there is significant interest in modeling their behavior. This talk will provide an overview of different types of shape memory polymers—in particular, crystallizable shape memory polymers and light-activated polymers. In crystallizable shape memory polymers, the temporary shape is fixed by a crystalline phase, while the return to the original shape is driven by the melting of this phase. For light-activated shape memory polymers, exposure to UV light at a specific frequency initiates the formation of cross-links that fix the temporary shape; exposure to UV light of a different frequency cleaves these cross-links, restoring the original shape. Specifically, we will focus on how these building blocks can be used to synthesize multi-shape memory polymers that respond to multiple stimuli, either sequentially or in tandem. As a result, complex shape changes and activation behaviors become possible, expanding the potential applications for these materials. Furthermore, we will discuss the underlying mechanisms and our approach to formulating constitutive equations that model the thermo-mechanical behavior of these polymers. The application of the developed models to different boundary-value problems of interest will be discussed. Finally, the model is implemented as a user material subroutine (UMAT) in the finite element software package ABAQUS. To demonstrate the applicability of the developed constitutive models, we numerically simulate three-dimensional geometries undergoing complex shape-fixation and recovery cycles.

Computer scienceMathematics

Audience: researchers in the topic

Modelling of materials - theory, model reduction and efficient numerical methods (UNCE MathMAC)