scholarly journals Triple-Shape Memory Behavior of Modified Lactide/Glycolide Copolymers

Polymers ◽  
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.

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

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.

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

2018 ◽  
Vol 29 (10) ◽  
pp. 2164-2176 ◽  
Author(s):  
R Abishera ◽  
R Velmurugan ◽  
KV Nagendra Gopal
Keyword(s):  
Glass Transition ◽  
Carbon Nanotube ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Shape Memory ◽  
Thermally Activated ◽  
Large Structures ◽  
Multi Walled Carbon Nanotube ◽  
Optical Strain Measurement ◽  
Optical Strain

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.

scholarly journals Modelling the Mechanical and Strain Recovery Behaviour of Partially Crystalline PLA

Polymers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1342 ◽  
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.

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

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.

Characterizing and Modeling the Free Recovery and Constrained Recovery Behavior of a Polyurethane Shape Memory Polymer

2010 ◽  
Author(s):  
Brent L. Volk ◽  
Dimitris C. Lagoudas ◽  
Duncan J. Maitland
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Shape Memory ◽  
Volume Fraction ◽  
Shape Memory Polymer ◽  
Tensile Tests ◽  
Stress Recovery ◽  
Shear Moduli ◽  
Recovery Experiment

In this work, tensile tests are performed on a polyurethane shape memory polymer for both free recovery (extension recovery at zero load) and constrained recovery (stress recovery at constant extension) conditions. The experimental characterization is conducted on an electromechanical screw driven test frame, and a laser extensometer is used in conjunction with the electromechanical frame to provide a non-contact technique for measuring the deformation of the material. The specimens are deformed, above the glass transition temperature, to 10% extension. The SMP is then cooled, at a constant value of extension, to below the glass transition temperature to ‘lock’ the temporary shape. The extension recovery at zero load as well as the stress recovery at a constant value of extension is measured during the first shape memory cycle as the SMP is heated to above its glass transition temperature. The material is observed to recover 93% of the applied deformation when heated at zero load. In addition, a stress recovery of 1.5 MPa is observed when heated while holding a constant value of deformation (10% extension). After performing the experiments, the Chen and Lagoudas model, implemented in 1-D by Volk, et al., is used to simulate and predict the experimental results. The material properties used in the model — namely the coefficients of thermal expansion, shear moduli, and frozen volume fraction — are calibrated from a single free recovery experiment. The calibrated model is then used to simulate the material response for the free recovery tests as well as predict the response for the constrained recovery condition. The model simulations agree well with the free recovery experimental data but predict a larger compressive stress than what is observed during the constrained recovery experiment.

scholarly journals Advanced Infill Designs for 3D Printed Shape-Memory Components

Micromachines ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1225
Author(s):  
Daniel Koske ◽  
Andrea Ehrmann
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Shape Memory ◽  
Fused Deposition Modeling ◽  
Shape Memory Polymer ◽  
The Other ◽  
Poly Lactic Acid ◽  
Fused Deposition ◽  
Other Hand

Poly(lactic acid) (PLA) is one of the most often used polymers in 3D printing based on the fused deposition modeling (FDM) method. On the other hand, PLA is also a shape memory polymer (SMP) with a relatively low glass transition temperature of ~60 °C, depending on the exact material composition. This enables, on the one hand, so-called 4D printing, i.e., printing flat objects which are deformed afterwards by heating them above the glass transition temperature, shaping them and cooling them down in the desired shape. On the other hand, objects from PLA which have been erroneously deformed, e.g., bumpers during an accident, can recover their original shape to a certain amount, depending on the applied temperature, the number of deformation cycles, and especially on the number of broken connections inside the object. Here, we report on an extension of a previous study, investigating optimized infill designs which avoid breaking in 3-point bending tests and thus allow for multiple repeated destruction and recovery cycles with only a small loss in maximum force at a certain deflection.

Curved Type Pneumatic Artificial Rubber Muscle Using Shape-Memory Polymer

2012 ◽  
Vol 24 (3) ◽  
pp. 472-479 ◽  
Author(s):  
Kazuto Takashima ◽  
◽  
Toshiro Noritsugu ◽  
Jonathan Rossiter ◽  
Shijie Guo ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Shape Memory ◽  
External Force ◽  
Shape Memory Polymer ◽  
Fiber Reinforcement ◽  
Artificial Muscle ◽  
Pneumatic Artificial Muscle ◽  
Initial Shape

A novel pneumatic artificial muscle actuator is presented which is based on the design of a conventional curved type pneumatic bellows actuator. By inhibiting the extension of one side with fiber reinforcement, bending motion can be induced when air is supplied to the internal bladder. In this study, we developed a new actuator by replacing the fiber reinforcement with a Shape-Memory Polymer (SMP). The SMP can be deformed above its glass transition temperature (Tg) and maintains a rigid shape after it is cooled below Tg. When next heated above Tg, it returns to its initial shape. When only part of our actuator is warmed above Tg, only that portion of the SMP is soft and can actuate. Therefore, the direction of the motion can be controlled by heating. Moreover, our actuator can be deformed by an external force above Tg and fixed by cooling it below Tg.

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