Unraveling the impact of phase separation induced by thermal annealing on shape memory effect of polyester‐based thermoplastic polyurethane

2021 ◽  
pp. 51723
Author(s):  
Fernanda Cabrera Flores Valim ◽  
Gustavo Peixoto Oliveira ◽  
Gibran Vasconcelos ◽  
Lucilene Betega Paiva ◽  
Chiara Santillo ◽  
...  
Keyword(s):  
Phase Separation ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Thermal Annealing ◽  
Memory Effect ◽  
Thermoplastic Polyurethane ◽  
The Impact

On the impact of lattice parameter accuracy of atomistic simulations on the microstructure of Ni-Ti shape memory alloys

2021 ◽  
Author(s):  
Lorenzo La Rosa ◽  
Francesco Maresca
Keyword(s):  
Molecular Dynamics ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Lattice Parameter ◽  
Lattice Parameters ◽  
Atomistic Simulations ◽  
Interatomic Potentials ◽  
The Impact

Abstract Ni-Ti is a key shape memory alloy (SMA) system for applications, being cheap and having good mechanical properties. Recently, atomistic simulations of Ni-Ti SMAs have been used with the purpose of revealing the nano-scale mechanisms that control superelasticity and the shape memory effect, which is crucial to guide alloying or processing strategies to improve materials performance. These atomistic simulations are based on molecular dynamics modelling that relies on (empirical) interatomic potentials. These simulations must reproduce accurately the mechanism of martensitic transformation and the microstructure that it originates, since this controls both superelasticity and the shape memory effect. As demonstrated by the energy minimization theory of martensitic transformations [Ball, James (1987) Archive for Rational Mechanics and Analysis, 100:13], the microstructure of martensite depends on the lattice parameters of the austenite and the martensite phases. Here, we compute the bounds of possible microstructural variations based on the experimental variations/uncertainties in the lattice parameter measurements. We show that both density functional theory and molecular dynamics lattice parameters are typically outside the experimental range, and that seemingly small deviations from this range induce large deviations from the experimental bounds of the microstructural predictions, with notable cases where unphysical microstructures are predicted to form. Therefore, our work points to a strategy for benchmarking and selecting interatomic potentials for atomistic modelling of shape memory alloys, which is crucial to modelling the development of martensitic microstructures and their impact on the shape memory effect.

scholarly journals Thermoresponsive Shape Memory Fibers for Compression Garments

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2989
Author(s):  
Robert Tonndorf ◽  
Dilbar Aibibu ◽  
Chokri Cherif
Keyword(s):  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Thermoplastic Polyurethane ◽  
Shape Memory Polymers ◽  
Strain Recovery ◽  
Recovery Stress ◽  
Compression Garments ◽  
Melt Spun ◽  
Shape Memory Fibers

Their highly deformable properties make shape memory polymers (SMP) a promising component for the development of new compression garments. The shape memory effect (SME) can be observed when two polymers are combined. In here, polycaprolactone (PCL) and thermoplastic polyurethane (TPU) were melt spun in different arrangement types (blend, core-sheath, and island-in-sea), whereas the best SME was observed for the blend type. In order to trigger the SME, this yarn was stimulated at a temperature of 50 °C. It showed a strain fixation of 62%, a strain recovery of 99%, and a recovery stress of 2.7 MPa.

Celite-mediated linking of polyurethane block copolymers and the impact on the shape memory effect

2010 ◽  
Vol 115 (6) ◽  
pp. 3568-3575 ◽  
Author(s):  
Yong-Chan Chung ◽  
Byoung Chul Chun ◽  
Sang Do Lee ◽  
Jong Shin Park
Keyword(s):  
Block Copolymers ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
The Impact

scholarly journals PU/PMMA composites synthesized by reaction-induced phase separation: a general approach to achieve a shape memory effect

RSC Advances ◽  
2017 ◽  
Vol 7 (54) ◽  
pp. 33701-33707 ◽  
Author(s):  
Yufen Zhang ◽  
Weiwei Li ◽  
Ronglan Wu ◽  
Wei Wang
Keyword(s):  
Phase Separation ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Polymethyl Methacrylate ◽  
Memory Effect ◽  
Shape Memory Polymer ◽  
Polymer Composition ◽  
Triple Shape Memory

We report a study on the triple-shape memory polymer composition of polyurethane/polymethyl methacrylate (PU/PMMA) synthesized using reaction-induced phase separation.

Tensile Failure of 55-Nitinol Wire

1975 ◽  
Vol 33 ◽  
pp. 46-47
Author(s):  
F. I. Grace
Keyword(s):  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Stoichiometric Composition ◽  
Tensile Failure ◽  
Initial State ◽  
Initial Shape ◽  
Nitinol Wire ◽  
Cscl Type ◽  
Shear Transformation

An interest in NiTi alloys with near stoichiometric composition (55 NiTi) has intensified since they were found to exhibit a unique mechanical shape memory effect at the Naval Ordnance Laboratory some twelve years ago (thus refered to as NITINOL alloys). Since then, the microstructural mechanisms associated with the shape memory effect have been investigated and several interesting engineering applications have appeared.The shape memory effect implies that the alloy deformed from an initial shape will spontaneously return to that initial state upon heating. This behavior is reported to be related to a diffusionless shear transformation which takes place between similar but slightly different CsCl type structures.

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