Modeling and Simulation of Large Microstructured Particles in Magnetic‐Shape‐Memory Composites

Conti, Sergio; Lenz, Martin; Rumpf, Martin

doi:10.1002/adem.201200048

Cited by 4 publications

(4 citation statements)

References 18 publications

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“…Certain ferromagnetic particles with an appropriate diameter generate heat by only hysteresis loss mechanism and enable an innate thermoregulation caused by the Curie temperature ( T C ). These ferromagnetic particles are able to heat a material up to T C (i.e., the ferromagnetic material becomes paramagnetic and loses its ability to generate heat via a hysteresis loss mechanism) 33, 176. By selecting a ferromagnetic particle material with a T C within safe medical limits, the danger of over heating in in‐vivo applications can be eliminated.…”

Section: Multifunctionality Of Shape‐memory Polymersmentioning

confidence: 99%

Multifunctional Shape‐Memory Polymers

2010

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The thermally‐induced shape‐memory effect (SME) is the capability of a material to change its shape in a predefined way in response to heat. In shape‐memory polymers (SMP) this shape change is the entropy‐driven recovery of a mechanical deformation, which was obtained before by application of external stress and was temporarily fixed by formation of physical crosslinks. The high technological significance of SMP becomes apparent in many established products (e.g., packaging materials, assembling devices, textiles, and membranes) and the broad SMP development activities in the field of biomedical as well as aerospace applications (e.g., medical devices or morphing structures for aerospace vehicles). Inspired by the complex and diverse requirements of these applications fundamental research is aiming at multifunctional SMP, in which SME is combined with additional functions and is proceeding rapidly. In this review different concepts for the creation of multifunctionality are derived from the various polymer network architectures of thermally‐induced SMP. Multimaterial systems, such as nanocomposites, are described as well as one‐component polymer systems, in which independent functions are integrated. Future challenges will be to transfer the concept of multifunctionality to other emerging shape‐memory technologies like light‐sensitive SMP, reversible shape changing effects or triple‐shape polymers.

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Section: Multifunctionality Of Shape‐memory Polymersmentioning

confidence: 99%

Multifunctional Shape‐Memory Polymers

2010

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“…In closing, we observe that the assumption that the particles are affinely deformed, which has a strong influence on the results presented and is only appropriate for very small particles, can be relaxed. In particular, in [CLR12] we discussed a variant of this model in which the particles are assumed to be large with respect to the scale of the individual domains, so that three scales are present: the scale of a microstructure inside a single particle, the scale of the individual particles interacting with the polymer, and the scale on which macroscopic material properties are observed and measured. Furthermore, in [CLR16] a time-dependent extension of the model was developed, assuming that two elastic phases are present inside each particles; the phase boundaries then move in response to the applied magnetic field.…”

Section: Discussionmentioning

confidence: 99%

“…Some of these results are discussed, also in view of the new homogenization result, in Section 4. The relaxation of the model, which is appropriate for situations where the particles are much larger than the domain size, has been addressed in [CLR12]. Our model was extended to the study of time-dependent problems, in a setting in which each particle changes gradually from one phase to the other, in [CLR16].…”

Section: Introductionmentioning

confidence: 99%

Homogenization in Magnetic-Shape-Memory Polymer Composites

Conti

Lenz

Pawelczyk

et al. 2018

Shape Optimization, Homogenization and Optimal Control

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Magnetic-shape-memory materials (e.g. specific NiMnGa alloys) react with a large change of shape to the presence of an external magnetic field. As an alternative for the difficult to manifacture single crystal of these alloys we study composite materials in which small magnetic-shape-memory particles are embedded in a polymer matrix. The macroscopic properties of the composite depend strongly on the geometry of the microstructure and on the characteristics of the particles and the polymer.We present a variational model based on micromagnetism and elasticity, and derive via homogenization an effective macroscopic model under the assumption that the microstructure is periodic. We then study numerically the resulting cell problem, and discuss the effect of the microstructure on the macroscopic material behavior. Our results may be used to optimize the shape of the particles and the microstructure.

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“…micromagnetism and elasticity both in the limit of small particles which contain no twin boundaries [CLR07] and in the limit of large particles with a large number of twin boundaries [CLR12]. Both papers were restricted to a static setting and based on energy minimization without any account of time-dependent effects such as hysteresis.…”

Section: Introductionmentioning

confidence: 99%

Hysteresis in magnetic shape memory composites: Modeling and simulation

Conti

Lenz

Rumpf

2016

Journal of the Mechanics and Physics of Solids

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Magnetic shape memory alloys are characterized by the coupling between a structural phase transition and magnetic one. This permits to control the shape change via an external magnetic field, at least in single crystals. Composite materials with single-crystalline particles embedded in a softer matrix have been proposed as a way to overcome the blocking of the transformation at grain boundaries.We investigate hysteresis phenomena for small NiMnGa single crystals embedded in a polymer matrix for slowly varying magnetic fields. The evolution of the microstructure is studied within the rate-independent variational framework proposed by Mielke and Theil (1999). The underlying variational model incorporates linearized elasticity, micromagnetism, stray field and a dissipation term proportional to the volume swept by the phase boundary. The time discretization is based on an incremental minimization of the sum of energy and dissipation. A backtracking approach is employed to approximately ensure the global minimality condition.We illustrate and discuss the influence of the particle geometry (volume fraction, shape, arrangement) and the polymer elastic parameters on the observed hysteresis and compare with recent experimental results.

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Modeling and Simulation of Large Microstructured Particles in Magnetic‐Shape‐Memory Composites

Cited by 4 publications

References 18 publications

Multifunctional Shape‐Memory Polymers

Multifunctional Shape‐Memory Polymers

Homogenization in Magnetic-Shape-Memory Polymer Composites

Hysteresis in magnetic shape memory composites: Modeling and simulation

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