Shape memory epoxy systems with a wide range of switching temperature

Entire or partial loss of function in the shoulder, elbow or wrist represent an increasingly common ailment connected to a wide range of injuries or other conditions including sports, occupational, spinal cord injuries or strokes. A general treatment of these problems relies on physiotherapy procedures. An increasing number of metallic materials are continuously being developed to expect the requirements for different engineering applications including biomedical field. Few constructive models that can involve intelligent materials are analyzed to establish the advantages in usage of shape memory elements mechanical implementation. The shape memory effect, superelasticity and damping capacity are unique characteristics at metallic alloys which demand careful consideration in both design and manufacturing processes. The actual rehabilitation systems can be improved using smart elements in motorized equipments like robotic systems. Shape memory alloys, especially NiTi (nitinol), represent a very good alternative for actuation in equipments with moving dispositive based on very good actuation properties, low mass, small size, safety and user friendliness. In this article the actuation and the force characteristics were analyzed to investigate a relationship between the bending angle and the actuation real value.

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Controlling the Switching Temperature of Biodegradable, Amorphous, Shape-Memory Poly(rac-lactide)urethane Networks by Incorporation of Different Comonomers

Biomacromolecules ◽

10.1021/bm900038e ◽

2009 ◽

Vol 10 (4) ◽

pp. 975-982 ◽

Cited By ~ 97

Author(s):

Andreas Lendlein ◽

Jörg Zotzmann ◽

Yakai Feng ◽

Armin Alteheld ◽

Steffen Kelch

Keyword(s):

Shape Memory ◽

Switching Temperature

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A simplified analytical model to simulate martensite reorientation and plasticity in shape memory alloy ring couplers

Journal of Intelligent Material Systems and Structures ◽

10.1177/1045389x211057215 ◽

2021 ◽

pp. 1045389X2110572

Author(s):

Fabrizio Niccoli ◽

Valentina Giovinco ◽

Cedric Garion ◽

Carmine Maletta ◽

Paolo Chiggiato

Keyword(s):

Shape Memory Alloy ◽

Shape Memory ◽

Analytical Model ◽

High Vacuum ◽

Ring Expansion ◽

Particle Accelerators ◽

European Organization ◽

Elastic Plastic ◽

Wide Range ◽

Martensite Reorientation

Recent studies on Shape Memory Alloy rings have been undertaken at the European Organization for Nuclear Research (CERN) to develop smart and leak-tight couplers for Ultra High Vacuum systems of particle accelerators. A special thermo-mechanical process (training) is needed to provide SMA rings with proper functional properties, that is to allow thermal mounting, dismounting, and leak tight coupling within a given service temperature window. Low temperature ring expansion is a crucial part of the training process as it gives suitable size, shape recovery properties, and thermal stability range to the SMA element. An analytical model, based on simplified elastic-plastic axisymmetric concepts, has been developed and implemented in a commercial software to simulate isothermal SMA rings expansions. It is particularly useful to predict the final size of a martensitic SMA coupler as a function of the initial dimensions and of the pre-deformation parameters. The effectiveness of the model has been demonstrated by analyzing the stress/deformation field occurring in a wide range of ring geometries for different load cases including martensite reorientation and plasticity. The predictions of the analytical model have been systematically compared with those obtained by axisymmetric finite element (FE) analyses based on elastic-plastic constitutive models and experimental measurements.

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Shape-Memory Polymers for Biomedical Applications

Advances in Science and Technology ◽

10.4028/www.scientific.net/ast.54.96 ◽

2008 ◽

Vol 54 ◽

pp. 96-102 ◽

Cited By ~ 33

Author(s):

Andreas Lendlein ◽

Marc Behl

Keyword(s):

Shape Memory ◽

Material Properties ◽

Biomedical Applications ◽

Traditional Approach ◽

Shape Change ◽

Shape Memory Polymers ◽

Thermally Induced ◽

Wide Range ◽

Multifunctional Polymers ◽

Suitable Process

Most polymers used in clinical applications today are materials that have been developed originally for application areas other than biomedicine. On the other side, different biomedical applications are demanding different combinations of material properties and functionalities. Compared to the intrinsic material properties, a functionality is not given by nature but result from the combination of the polymer architecture and a suitable process. Examples for functionalities that play a prominent role in the development of multifunctional polymers for medical applications are biofunctionality (e.g. cell or tissue specificity), degradability, or shape-memory functionality. In this sense, an important aim for developing multifunctional polymers is tailoring of biomaterials for specific biomedical applications. Here the traditional approach, which is designing a single new homo- or copolymer, reaches its limits. The strategy, that is applied here, is the development of polymer systems whose macroscopic properties can be tailored over a wide range by variation of molecular parameters. The Shape-memory capability of a material is its ability to trigger a predefined shape change by exposure to an external stimulus. A change in shape initiated by heat is called thermally-induced shape-memory effect. Thermally, light-, and magnetically induced shape-memory polymers will be presented, that were developed especially for minimally invasive surgery and other biomedical applications. Furthermore triple-shape polymers will be introduced, that have the capability to perform two subsequent shape changes. Thus enabling more complex movements of a polymeric material.

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Micro pulling down growth of very thin shape memory alloys single crystals

Functional Materials Letters ◽

10.1142/s1793604717400033 ◽

2017 ◽

Vol 10 (01) ◽

pp. 1740003 ◽

Cited By ~ 1

Author(s):

I. López-Ferreño ◽

J. San Juan ◽

T. Breczewski ◽

G. A. López ◽

M. L. Nó

Keyword(s):

Mechanical Properties ◽

Shape Memory Alloys ◽

Single Crystal ◽

Shape Memory ◽

Single Crystals ◽

Functional Materials ◽

Small Scale ◽

Cylindrical Shape ◽

Minimum Diameter ◽

Wide Range

Shape memory alloys (SMAs) have attracted much attention in the last decades due to their thermo-mechanical properties such as superelasticity and shape memory effect. Among the different families of SMAs, Cu–Al–Ni alloys exhibit these properties in a wide range of temperatures including the temperature range of 100–200[Formula: see text]C, where there is a technological demand of these functional materials, and exhibit excellent behavior at small scale making them more competitive for applications in Micro Electro-Mechanical Systems (MEMS). However, polycrystalline alloys of Cu-based SMAs are very brittle so that they show their best thermo-mechanical properties in single-crystal state. Nowadays, conventional Bridgman and Czochralski methods are being applied to elaborate single-crystal rods up to a minimum diameter of 1[Formula: see text]mm, but no works have been reported for smaller diameters. With the aim of synthesizing very thin single-crystals, the Micro-Pulling Down ([Formula: see text]-PD) technique has been applied, for which the capillarity and surface tension between crucible and the melt play a critical role. The [Formula: see text]-PD method has been successfully applied to elaborate several cylindrical shape thin single-crystals down to 200[Formula: see text][Formula: see text]m in diameter. Finally, the martensitic transformation, which is responsible for the shape memory properties of these alloys, has been characterized for different single-crystals. The experimental results evidence the good quality of the grown single-crystals.

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Mechanical Deformation of Field-Coupled Materials

Adaptive Structures and Materials Systems ◽

10.1115/imece2002-39009 ◽

2002 ◽

Author(s):

Pavel M. Chaplya ◽

Geoffrey P. McKnight ◽

Gregory P. Carman

Keyword(s):

Shape Memory ◽

Smart Materials ◽

Residual Strain ◽

Applied Load ◽

Mechanical Response ◽

Volume Fraction ◽

Mechanical Deformation ◽

Passive Damping ◽

Wide Range ◽

Internal States

This article describes remarkable similarities in the nonlinear mechanical response of different active/smart materials despite fundamental differences in the underlying mechanisms associated with each material. Active/smart materials (i.e., piezoelectric (PZT-5H), magnetostrictive (Terfenol-D), and shape memory alloys (NiTi)) exhibit strong non-linear mechanical behavior produced by changing non-mechanical internal states such as polarization, magnetization, and phase/twin configuration. In active/smart materials the initial deformation proceeds linearly followed by a jump in strain associated with the transformation of an internal non-mechanical state. After the transformation, the mechanical response returns to linear elastic. Upon unloading, a residual strain is observed which can be recovered with the application of a corresponding external field (i.e., electric, magnetic, or thermal). Due to coupling between applied fields and non-mechanical internal states, mechanical deformation is also a function of applied external fields. At a critical applied field, the residual strain is eliminated, providing repeatable cyclic characteristics that can be used in passive damping applications. Even though different intrinsic processes (i.e., polarization, magnetization, and phase/twin variant composition) govern the deformation of each material, their macroscopic behavior is explained using a unified volume fraction concept. That is, the deformation of piezoelectric material is described in terms of the volume fraction of ferroelectric domains with polarization parallel or orthogonal to the applied load; the deformation of magnetostrictive materials is described in terms of the volume fraction of magnetic domains with magnetization parallel or orthogonal to the applied load; and the deformation of shape memory material is described in terms of the volume fraction of twin variants that are oriented favorably to the applied load. Although the qualitative behavior of each material is similar, the average magnitude of stress required to induce non-linearity varies from ~10 MPa for Terfenol-D to ~65 MPa for PZT-5H to ~300 MPa for NiTi shape memory alloy. It is hypothesized that a composite material made of these materials connected in series would exhibit passive damping over a wide range of applied stress.

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Shape-Memory Polymeric Artificial Muscles: Mechanisms, Applications and Challenges

Molecules ◽

10.3390/molecules25184246 ◽

2020 ◽

Vol 25 (18) ◽

pp. 4246 ◽

Cited By ~ 1

Author(s):

Yujie Chen ◽

Chi Chen ◽

Hafeez Ur Rehman ◽

Xu Zheng ◽

Hua Li ◽

...

Keyword(s):

Shape Memory ◽

Smart Materials ◽

Recent Progress ◽

Shape Memory Polymer ◽

Shape Memory Polymers ◽

Artificial Muscles ◽

Linkage Design ◽

Wide Range ◽

Liquid Crystal Elastomers ◽

Made In

Shape-memory materials are smart materials that can remember an original shape and return to their unique state from a deformed secondary shape in the presence of an appropriate stimulus. This property allows these materials to be used as shape-memory artificial muscles, which form a subclass of artificial muscles. The shape-memory artificial muscles are fabricated from shape-memory polymers (SMPs) by twist insertion, shape fixation via Tm or Tg, or by liquid crystal elastomers (LCEs). The prepared SMP artificial muscles can be used in a wide range of applications, from biomimetic and soft robotics to actuators, because they can be operated without sophisticated linkage design and can achieve complex final shapes. Recently, significant achievements have been made in fabrication, modelling, and manipulation of SMP-based artificial muscles. This paper presents a review of the recent progress in shape-memory polymer-based artificial muscles. Here we focus on the mechanisms of SMPs, applications of SMPs as artificial muscles, and the challenges they face concerning actuation. While shape-memory behavior has been demonstrated in several stimulated environments, our focus is on thermal-, photo-, and electrical-actuated SMP artificial muscles.

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Ability to Control the Glass Transition Temperature of Amorphous Shape-Memory Polyesterurethane Networks by Varying Prepolymers in Molecular Mass as well as in Type and Content of Incorporated Comonomers

MRS Proceedings ◽

10.1557/proc-1190-nn01-09 ◽

2009 ◽

Vol 1190 ◽

Author(s):

Joerg Zotzmann ◽

Steffen Kelch ◽

Armin Alteheld ◽

Marc Behl ◽

Andreas Lendlein

Keyword(s):

Glass Transition ◽

Minimally Invasive Surgery ◽

Shape Memory ◽

Molecular Mass ◽

Amorphous Polymer ◽

Polymer Networks ◽

Precise Control ◽

Low Weight ◽

Switching Temperature ◽

Selection Of

AbstractThe need of intelligent implant materials for applications in the area of minimally invasive surgery leads to tremendous attention for polymers which combine degradability and shape-memory capability. Application of heat, and thereby exceeding a certain switching temperature Tsw, causes the device to changes its shape. The precise control of Tsw is particularly challenging. It was investigated in how far Tg, that can be used as Tsw, of amorphous polymer networks from star-shaped polyester macrotetrols crosslinked with a low-weight linker can be controlled systematically by incorporation of different comonomers into poly(rac-lactide) prepolymers. The molecular mass of the prepolymers as well as type and content of the comonomers was varied. The Tg could be adjusted by selection of comonomer type and ratio without affecting the advantageous elastic properties of the polymer networks.

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The Interaction of Point Defects with the Martensitic Transformation: A Prototype of Exotic Multiscale Phenomena

MRS Bulletin ◽

10.1557/mrs2002.47 ◽

2002 ◽

Vol 27 (2) ◽

pp. 116-120 ◽

Cited By ~ 21

Author(s):

Xiaobing Ren ◽

Kazuhiro Otsuka

Keyword(s):

Martensitic Transformation ◽

Shape Memory ◽

Point Defects ◽

Symmetry Property ◽

Short Range ◽

Domain Pattern ◽

Wide Range ◽

Mesoscopic Level ◽

Martensitic Materials ◽

Rich Spectrum

AbstractThe martensitic transformation has so far been studied without considering its interaction with point defects. In this article, we shall show that such interaction, which stems from a universal symmetry property of point defects, can create a rich spectrum of exotic multiscale phenomena in martensitic materials. These phenomena include unique short-range diffusion at the atomic or nano level, remarkable domain-pattern memory at the mesoscopic level, and peculiar rubber-like behavior and aging-induced two-way shape memory at the macroscopic level. Exotic multiscale phenomena may also be found in a wide range of transforming materials, such as ferroelastic, ferroelectric, and ferromagnetic materials. These novel effects may provide new opportunities for these important materials.

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Vibration Characteristics of Composite Plate Embedded with Shape Memory Alloy at Elevated Temperature

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.393.655 ◽

2013 ◽

Vol 393 ◽

pp. 655-660 ◽

Cited By ~ 7

Author(s):

Izzuddin Zaman ◽

Bukhari Manshoor ◽

Amir Khalid ◽

Sherif Araby ◽

Mohd Imran bin Ghazali

Keyword(s):

Shape Memory Alloy ◽

Shape Memory ◽

Composite Structures ◽

Composite Plate ◽

Free Vibration Analysis ◽

Composite Plates ◽

Vibration Characteristics ◽

Modal Testing ◽

Phase Transformation Temperature ◽

Wide Range

Unique functional material of shape memory alloy has attracted tremendous interest from researches, thus has been broadly investigated for a wide range application. Current research effort extends the use of SMA for the design of smart composite structures due to its shape memory effect, pseudo-elasticity and high damping capability. This paper presents an assessment of applications of the SMA materials for structural vibration controls, where the influences of SMA as reinforcement in the composite plate at different temperature are investigated. Four cases of composite plate are studied, which two of them are SMA-based composite fabricated at 0° and 45° angles, and the other two plates are neat (without SMA wires) and built with local stiffener. By using modal testing, the free vibration analysis is carried out to determine the vibration characteristics of composite plates. The results show that infusing SMA wires into composites increased the natural frequencies of the plate considerably, while decreased slightly for damping percentage. However, when SMA wires are heated, the damping percentage improved tremendously due to the phase transformation temperature of SMA from martensite to austenite. The outcome of this study reveals the potential of SMA materials in active vibration control.

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