Free, partial, and fully constrained recovery analysis of cold-programmed shape memory epoxy/carbon nanotube nanocomposites: Experiments and predictions

Thermally activated shape memory polymers are typically programmed by initially heating the material above the glass transition temperature ( Tg), deforming to the desired shape, cooling below Tg, and unloading to fix the temporary shape. This process of deforming at high temperatures becomes a time-, labor-, and energy-expensive process while applying to large structures. Alternatively, materials with reversible plasticity shape memory property can be programmed at temperatures well below the glass transition temperature which offers several advantages over conventional programming. Here, the free, partial, and fully constrained recovery analysis of cold-programmed multi-walled carbon nanotube–reinforced epoxy nanocomposites is presented. The free recovery analysis involves heating the temporary shape above Tg without any constraints (zero stress), and for fully constrained recovery analysis, the temporary shape is held constant while heating. The partially constrained recovery behavior is studied by applying a constant stress of 10%, 25%, and 50% of the maximum recovery stress obtained from the completely constrained recovery analysis. The samples are also characterized for their thermal, morphological, and mechanical properties. A non-contact optical strain measurement method is used to measure the strains during cold-programming and shape recovery. The different recovery behaviors are analyzed by using a thermo-viscoelastic–viscoplastic model, and the predictions are compared with the experimental results.

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Physical properties, thermal stability, and glass transition temperature of multi-walled carbon nanotube/polypyrrole nanocomposites

Composite Interfaces ◽

10.1080/15685543.2014.943020 ◽

2014 ◽

Vol 21 (8) ◽

pp. 737-747 ◽

Cited By ~ 10

Author(s):

Mansoor Farbod ◽

Nooshin Mobini

Keyword(s):

Thermal Stability ◽

Glass Transition ◽

Carbon Nanotube ◽

Transition Temperature ◽

Glass Transition Temperature ◽

Physical Properties ◽

Multi Walled Carbon Nanotube

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Development of Thermally-Activated Shape Memory Polymers and Nanocomposites for Biomedical Devices

Volume 3: Biomedical and Biotechnology Engineering ◽

10.1115/imece2017-72500 ◽

2017 ◽

Author(s):

Jingyu Wang ◽

Shoieb Chowdhury ◽

Yingtao Liu ◽

Bradley Bohnstedt ◽

Chung-Hao Lee

Keyword(s):

Mechanical Properties ◽

Carbon Nanotubes ◽

Glass Transition ◽

Transition Temperature ◽

Glass Transition Temperature ◽

Shape Memory ◽

Thermal Activation ◽

Memory Function ◽

Shape Memory Polymers ◽

Thermally Activated

Shape memory polymers (SMPs) have been developed as an emerging technology platform for biomedical applications in the past decades. In particular, SMPs are clinically essential for the development of novel medical devices to significantly improve long-term surgical outcomes. In this paper, we synthesized and characterized thermally-activated aliphatic urethane SMPs fabricated with nanocomposites for the design and development of biomedical devices. The thermal activation of shape memory function was investigated by direct thermal activation. Critical polymer properties, such as the glass transition temperature and shape memory function, have been tailored to desired applications, by adjusting the polymer composition. Carbon nanotubes were uniformly dispersed within the polymer during nanocomposite fabrication to significantly enhance the thermal and electrical properties. The synthesized SMPs and nanocomposites were characterized to understand their thermal and mechanical properties using dynamic mechanical analysis (DMA). Scanning electron microscopy was employed to evaluate the dispersion of carbon nanotubes in polymer matrix. The mechanical properties of SMPs and nanocomposites at temperature above their glass transition temperature were evaluated using dog-bone samples in a dual-column mechanical testing system and an environmental chamber. SMPs and nanocomposites will then be fabricated in the form of foam for the development of novel devices applicable to endovascular embolization of cerebral aneurysms.

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Buckling and vibration analysis of shape memory laminated composite beams under axially heterogeneous in-plane loads in the glass transition temperature region

SN Applied Sciences ◽

10.1007/s42452-021-04438-2 ◽

2021 ◽

Vol 3 (4) ◽

Author(s):

Nilesh Tiwari ◽

A. A. Shaikh

Keyword(s):

Glass Transition ◽

Transition Temperature ◽

Glass Transition Temperature ◽

Boundary Conditions ◽

Shape Memory ◽

Transition Region ◽

Shape Memory Polymer ◽

Shear Deformation Theory ◽

Effect Of Temperature ◽

Glass Transition Region

AbstractBuckling and vibration study of the shape memory polymer composites (SMPC) across the glass transition temperature under heterogeneous loading conditions are presented. Finite element analysis based on C° continuity equation through the higher order shear deformation theory (HSDT) is employed considering non linear Von Karman approach to estimate critical buckling and vibration for the temperature span from 273 to 373 K. Extensive numerical investigations are presented to understand the effect of temperature, boundary conditions, aspect ratio, fiber orientations, laminate stacking and modes of phenomenon on the buckling and vibration behavior of SMPC beam along with the validation and convergence study. Effect of thermal conditions, particularly in the glass transition region of the shape memory polymer, is considerable and presents cohesive relation between dynamic modulus properties with magnitude of critical buckling and vibration. Moreover, it has also been inferred that type of axial loading condition along with the corresponding boundary conditions significantly affect the buckling and vibration load across the glass transition region.

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Influence of Carbon Nanotube Aspect Ratio on Glass Transition Temperature of Polymers: A Molecular Dynamics Simulation Study

Materials Science Forum ◽

10.4028/www.scientific.net/msf.817.797 ◽

2015 ◽

Vol 817 ◽

pp. 797-802 ◽

Cited By ~ 2

Author(s):

Cai Jiang ◽

Jian Wei Zhang ◽

Shao Feng Lin ◽

Su Ju ◽

Da Zhi Jiang

Keyword(s):

Molecular Dynamics ◽

Glass Transition ◽

Carbon Nanotube ◽

Transition Temperature ◽

Glass Transition Temperature ◽

Aspect Ratio ◽

Epoxy Resin ◽

Md Simulations ◽

Diglycidyl Ether ◽

Dynamics Simulation

Molecular dynamics (MD) simulations on three single walled carbon nanotube (SWCNT) reinforced epoxy resin composites were conducted to study the influence of SWCNT type on the glass transition temperature (Tg) of the composites. The composite matrix is cross-linked epoxy resin based on the epoxy monomers bisphenol A diglycidyl ether (DGEBA) cured by diaminodiphenylmethane (DDM). MD simulations of NPT (constant number of particles, constant pressure and constant temperature) dynamics were carried out to obtain density as a function of temperature for each composite system. The Tg was determined as the temperature corresponding to the discontinuity of plot slopes of the densityvsthe temperature. In order to understand the motion of polymer chain segments above and below the Tg, various energy components and the MSD at various temperatures of the composites were investigated and their roles played in the glass transition process were analyzed. The results show that the Tg of the composites increases with increasing aspect ratio of the embedded SWCNT

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Triple-Shape Memory Behavior of Modified Lactide/Glycolide Copolymers

Polymers ◽

10.3390/polym12122984 ◽

2020 ◽

Vol 12 (12) ◽

pp. 2984

Author(s):

Anna Smola-Dmochowska ◽

Natalia Śmigiel-Gac ◽

Bożena Kaczmarczyk ◽

Michał Sobota ◽

Henryk Janeczek ◽

...

Keyword(s):

Glass Transition ◽

Transition Temperature ◽

Glass Transition Temperature ◽

Shape Memory ◽

Hydroxyl Groups ◽

Butylene Succinate ◽

Shape Memory Behavior ◽

Triple Shape Memory ◽

High Flexibility ◽

Bioresorbable Implants

The paper presents the formation and properties of biodegradable thermoplastic blends with triple-shape memory behavior, which were obtained by the blending and extrusion of poly(l-lactide-co-glycolide) and bioresorbable aliphatic oligoesters with side hydroxyl groups: oligo (butylene succinate-co-butylene citrate) and oligo(butylene citrate). Addition of the oligoesters to poly (l-lactide-co-glycolide) reduces the glass transition temperature (Tg) and also increases the flexibility and shape memory behavior of the final blends. Among the tested blends, materials containing less than 20 wt % of oligo (butylene succinate-co-butylene citrate) seem especially promising for biomedical applications as materials for manufacturing bioresorbable implants with high flexibility and relatively good mechanical properties. These blends show compatibility, exhibiting one glass transition temperature and macroscopically uniform physical properties.

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Modelling the Mechanical and Strain Recovery Behaviour of Partially Crystalline PLA

Polymers ◽

10.3390/polym11081342 ◽

2019 ◽

Vol 11 (8) ◽

pp. 1342 ◽

Cited By ~ 2

Author(s):

John Sweeney ◽

Paul Spencer ◽

Karthik Nair ◽

Phil Coates

Keyword(s):

Finite Element ◽

Glass Transition ◽

Transition Temperature ◽

Glass Transition Temperature ◽

Stress Relaxation ◽

Shape Memory ◽

Yield Stress ◽

Amorphous Phase ◽

Strain Recovery ◽

Stress Strain

This is a study of the modelling and prediction of strain recovery in a polylactide. Strain recovery near the glass transition temperature is the underlying mechanism for the shape memory in an amorphous polymer. The investigation is aimed at modelling such shape memory behaviour. A PLA-based copolymer is subjected to stress–strain, stress relaxation and strain recovery experiments at large strain at 60 °C just below its glass transition temperature. The material is 13% crystalline. Using published data on the mechanical properties of the crystals, finite element modelling was used to determine the effect of the crystal phase on the overall mechanical behaviour of the material, which was found to be significant. The finite element models were also used to relate the stress–strain results to the yield stress of the amorphous phase. This yield stress was found to possess strain rate dependence consistent with an Eyring process. Stress relaxation experiments were also interpreted in terms of the Eyring process, and a two-process Eyring-based model was defined that was capable of modelling strain recovery behaviour. This was essentially a model of the amorphous phase. It was shown to be capable of useful predictions of strain recovery.

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A carbon nanotube–epoxy interface improved damping below the glass transition temperature

RSC Advances ◽

10.1039/c6ra01239f ◽

2016 ◽

Vol 6 (25) ◽

pp. 21271-21276 ◽

Cited By ~ 6

Author(s):

Yung-Chi Chu ◽

Ming-Hsiao Weng ◽

Wen-Yi Lin ◽

Hsin-Jung Tsai ◽

Wen-Kuang Hsu

Keyword(s):

Glass Transition ◽

Carbon Nanotube ◽

Transition Temperature ◽

Glass Transition Temperature ◽

Room Temperature ◽

Viscous Drag

Composites made from fibers and epoxy display a low viscous drag and are rarely used as mechanical dampers at room temperature.

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A Molecular-Dynamics Study of Size and Chirality Effects on Glass-Transition Temperature and Ordering in Carbon Nanotube-Polymer Composites

Macromolecular Theory and Simulations ◽

10.1002/mats.201600041 ◽

2016 ◽

Vol 25 (6) ◽

pp. 571-581 ◽

Cited By ~ 7

Author(s):

Marcello Malagù ◽

Alexey Lyulin ◽

Elena Benvenuti ◽

Angelo Simone

Keyword(s):

Molecular Dynamics ◽

Glass Transition ◽

Carbon Nanotube ◽

Transition Temperature ◽

Glass Transition Temperature ◽

Polymer Composites

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Combined light- and heat-induced shape memory behavior of anthracene-based epoxy elastomers

Scientific Reports ◽

10.1038/s41598-020-77246-0 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Yuzhan Li ◽

Monojoy Goswami ◽

Yuehong Zhang ◽

Tuan Liu ◽

Jinwen Zhang ◽

...

Keyword(s):

Glass Transition ◽

Transition Temperature ◽

Glass Transition Temperature ◽

Shape Memory ◽

Uv Light ◽

Dynamic Mechanical Properties ◽

Stimuli Responsive ◽

Epoxy Monomer ◽

Dynamics Simulations ◽

External Stimuli

AbstractThe development of multi-stimuli-responsive shape memory polymers has received increasing attention because of its scientific and technological significance. In this work, epoxy elastomers with reversible crosslinks are synthesized by polymerizing an anthracene-functionalized epoxy monomer, a diepoxy comonomer, and a dicarboxylic acid curing agent. The synthesized elastomers exhibit active responses to both light and heat enabled by the incorporated anthracene groups. When exposed to 365 nm UV light, additional crosslinking points are created by the photo-induced dimerization of pendant anthracene groups. The formation of the crosslinking points increases modulus and glass transition temperature of the elastomers, allowing for the fixation of a temporary shape at room temperature. The temporary shape remains stable until an external heat stimulus is applied to trigger the scission of the dimerized anthracene, which reduces the modulus and glass transition temperature and allows the elastomers to recover their original shapes. The effects of external stimuli on the thermal and dynamic mechanical properties of the elastomers are investigated experimentally and are correlated with molecular dynamics simulations that reveal the changes of structure and dynamics of the anthracene molecules and flexible chains.

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