Constitutive modeling of the mechanics associated with crystallizable shape memory polymers

Shape memory polymers (SMP’s) are polymers that have the ability to retain a temporary shape, which can revert back to the original shape on exposure to specific triggers such as increase in temperature or exposure to light at specific wavelengths. A new type of shape memory polymer, light activated shape memory polymers (LASMP’s) have been developed in the past few years. In these polymers the temporary shapes are fixed by exposure to light at a specific wavelength. Exposure to light at this wavelength causes the photosensitive molecules, which are grafted on to the polymer chains, to form covalent bonds. These covalent bonds are responsible for the temporary shape and act as crosslinks. On exposure to light at a different wavelength these bonds are cleaved and the material can revert back to its original shape. A constitutive model of LASMP’s which based on the notion of multiple natural configurations has been developed (see Sodhi and Rao[1]). In this work we use this model to analyze the mechanical behavior of LASMP’s under a specific boundary value problem, namely, the problem of circular shear. We use this model problem to study the behavior of the LASMP’s when a temporary configuration is formed by exposing the polymer to light. In addition we show that these materials are able to undergo complex cycles of deformation due to the flexibility with which these temporary configurations can be formed and removed by exposure to light.

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Constitutive Modeling of multi-stimuli-responsive shape memory polymers with multi-functional capabilities

International Journal of Mechanical Sciences ◽

10.1016/j.ijmecsci.2020.106082 ◽

2021 ◽

Vol 192 ◽

pp. 106082

Author(s):

Mahdi Baniasadi ◽

Ebrahim Yarali ◽

Mahdi Bodaghi ◽

Ali Zolfagharian ◽

Mostafa Baghani

Keyword(s):

Shape Memory ◽

Constitutive Modeling ◽

Shape Memory Polymers ◽

Stimuli Responsive ◽

Functional Capabilities

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Constitutive Modeling of Shape Memory Effects in Semicrystalline Polymers With Stretch Induced Crystallization

Journal of Engineering Materials and Technology ◽

10.1115/1.4001964 ◽

2010 ◽

Vol 132 (4) ◽

Cited By ~ 63

Author(s):

Kristofer K. Westbrook ◽

Vikas Parakh ◽

Taekwoong Chung ◽

Patrick T. Mather ◽

Logan C. Wan ◽

...

Keyword(s):

Shape Memory ◽

Constitutive Modeling ◽

Three Dimensional ◽

Constitutive Models ◽

Shape Memory Polymers ◽

One Dimensional ◽

Chain Mobility ◽

Shape Memory Effects ◽

External Stimuli ◽

Induced Crystallization

Polymers can demonstrate shape memory (SM) effects by being temporarily fixed in a nonequilibrium shape and then recover their permanent shape when exposed to heat, light, or other external stimuli. Many previously developed shape memory polymers (SMPs) use the dramatic molecular chain mobility change around the glass transition temperature Tg to realize the SM effect. In these materials, the temporary shape cannot be repeated unless it is reprogramed, and therefore the SM effect is one way. Recently, a semicrystalline SMP, which can demonstrate both one- and two-way SM effects, was developed by one of our groups (Chung, T., Rorno-Uribe, A., and Mather, P. T., 2008, “Two-Way Reversible Shape Memory in a Semicrystalline Network,” Macromolecules, 41(1), pp. 184–192). The main mechanism of the observed SM effects is due to stretch induced crystallization. This paper develops a one-dimensional constitutive model to describe the SM effect due to stretch induced crystallization. The model accurately describes the complex thermomechanical SM effect and can be used for the future development of three-dimensional constitutive models.

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