A Viscoelastic-Plastic Constitutive Model of Shape Memory Polymer

Abstract

It is of practical significance to develop a constitutive model which is able to predict the thermomechanical behaviors of the shape memory effect occurring in a shape memory polymer (SMP) accurately. The mechanism of shape memory effect of SMP is explained based on the assumption that SMP is composed by two phases, reversible phase and stationary phase. Especially the different flow elements are respectively added to the reversible phase and stationary phase in order to express the plastic behavior of SMP. There are two springs in series, one dashpot and one flow element in the reversible phase. There are two springs in parallel, one dashpot and one flow element in the stationary phase. A constitutive equation is developed to express the thermo-mechanical behaviors of shape memory effect in the SMP based on viscous-elastic mechanics and plastic theory. An internal variable, frozen ratio, is defined to follow the shape memory process in SMP, and the material properties are described as the functions of frozen ratio based on phase transition theorem. The developed constitutive model, which includes above constitutive equation and material parameter functions, is used to numerically simulate the thermo-mechanical behaviors of SMP under various load cycles. Results show that the developed constitutive model can not only predict the shape memory process of SMP accurately, but also express the rate-dependent behaviors of SMP effectively.

Theoretical solutions of short glass fiber/polyurethane composite beams based on Hamiltonian principle

“…Liu et al 13 systematically investigated the thermodynamic behavior of epoxy resins during the storage and recovery processes under uniaxial tension and compression at small strains, and developed a three-dimensional small-strain internal variable constitutive model based on experimental results. Zheng et al 14 introduced different flow units to the reversible and steady phases of SMP, characterized their plastic behavior, explained the shape memory mechanism, established a new constitutive model, and studied the thermodynamic behavior of SMP. Based on rubber elasticity and relaxation theory, Lu et al 15 studied the swelling induced shape recovery mechanism and complex shape memory behavior in solvent-based SMP using free energy function.…”

In Situ Construction of Thermotropic Shape Memory Polymer in Wood for Enhancing Its Dimensional Stability

“…It is generally composed of a stationary and reversible phase and can soften and harden reversibly at a specific temperature. The function of the stationary phase is to memorize and restore the initial form, while the reversible phase completes the deformation and fixation [20,21]. When the environmental temperature exceeds its transition temperature (T trans ), i.e., the glass transition (T g ) or melting temperature (T m ), the SMP becomes soft and deforms under external force.…”

Modeling size-dependent thermal-mechanical behaviors of shape memory polymer Timoshenko micro-beam

“…Shape memory polymer is a kind of smart material which has the ability to recover the deformed and fixed shape to the original shape under external stimulation. The shape memory phenomenon is triggered by the stimulus such as light (Miao et al , 2020), heat (Zheng et al , 2019), electromagnetic field (Kong et al , 2020) and special chemical substances (Wang et al , 2019). Due to its strong deformation ability, excellent biodegradability, biocompatibility and good manufacturing performance, shape memory polymer has a good application prospect in the fields of MEMS (Gao et al , 2019), biomedicine (Maiti et al , 2018), aerospace (Liu et al , 2014) and so on, and thermal responsive shape memory polymers are one of the research hotspots because of their characteristics of easy to trigger shape memory process and easy to control deformation.…”

“…On the basis of this work, Li and Liu (2018) further developed the SMP constitutive model combining phase transition and viscoelasticity, which can not only characterize the viscoelasticity and rate-dependent behavior of SMP, but also physically connect the shape memory effect with the glass transition. Zheng et al (2019) added the different flow elements respectively to the reversible phase and stationary phase to express the plastic behavior of SMP.…”