Modeling the response of light-activated shape memory polymers

Abstract

The aim of this paper is to model the macroscopic response of light-activated shape memory polymers (LASMPs) subject to mechanical loadings and exposure to light at certain wavelengths and frequencies. When exposed to external stimuli of mechanical, thermal, photochemical and other origins, polymers undergo microstructural changes, e.g., scission, crosslinking, crystallization, etc. These microstructural changes affect the macroscopic performance of the polymers. In this study, in order to incorporate the effect of microstructural changes on the macroscopic response of light-activated shape memory polymers, we formulate constitutive models based on the notion that the natural configuration of the body under consideration evolves during its response. The theoretical framework appeals to a multinetwork approach consisting of two microstructural networks, which are the original network and the new network formed owing to a light activation. An important distinction between the approach considered here and the usual multinetwork approaches is that there is no conversion of one network to another; instead, what we have is the formation of a second network owing to the linking of photosensitive particles that get linked due to light irradiation. Furthermore, two different constitutive models are considered. The first model assumes the two networks are isotropic. The second model takes into account the directional preference of the second network that is formed. Both these models build on the work of Sodhi and Rao, which is based on the framework developed by Rajagopal and Srinivasa. Several classical boundary value problems involving homogeneous and inhomogeneous deformations are studied. We also investigate two nonlinear constitutive relations and different loading modes. The results highlight the differences in the responses when isotropic and anisotropic models are considered.

A comprehensive review on thermomechanical constitutive models for shape memory polymers

“…light-responsive or pH-sensitive SMPs, etc.). For instance, for details on light-sensitive SMPs, one may refer to Hamel et al (2017), Long et al (2009), Sodhi and Rao (2010), Yuan et al (2017), and Zhi et al (2017). Xiao et al (2016b) developed a constitutive model for an SMP responsive to dissolution.…”

Quasi-linear viscoelastic modeling of light-activated shape memory polymers

“…In our previous study (Yuan et al, 2016), we modeled the response of the LASMPs based on the assumption that the LASMPs have multiple natural configurations within the context of elastic response. However, as discussed above, the LASMPs are polymers which may exhibit viscoelasticity, In order to investigate such response we adopt the quasi-linear viscoelasticity framework to model the behavior of LASMPs.…”

“…In our earlier study (Yuan et al, 2016), we discussed the development of both isotropic and anisotropic constitutive models to describe the elastic response of LASMPs for thin samples based on the notion of multiple natural configurations (see Rajagopal, 1995 for a discussion of the role of natural configuration in constitutive theories). By considering several boundary value problems, we highlighted the differences caused by the anisotropy due to the formation of the second network.…”

“…By considering several boundary value problems, we highlighted the differences caused by the anisotropy due to the formation of the second network. In our earlier study (Yuan et al, 2016), the viscoelasticity of LASMPs, which many such materials exhibit, was ignored. Although limited, there have been experimental studies on LASMPs from which we can gain some idea concerning the stress relaxation that is exhibited by such materials.…”

Investigation of the strain‐rate‐dependent mechanical behavior of a photopolymer matrix composite with fumed nano‐silica filler

“…Muliana et al presented a modified form of QLV models in which they expressed strain as an integral of a nonlinear measure of the stress. They predicted the behavior of elastomers and light‐activated shape memory polymers using these models . The QLV model is commonly employed nowadays because it provides the simplest way to include both nonlinearity (dependence of properties of load or strain) and time dependence (viscoelasticity) in a simplified integral model.…”