Bridging from particle to macroscopic scales in uniaxial magnetic gels

Menzel, Andreas M.

doi:10.1063/1.4901275

Cited by 39 publications

(29 citation statements)

References 74 publications

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“…1a). For initialization, we arrange the particles in straight linear chain-like aggregates: each chain is one particle in diameter, but several equi-distanced particles in length that are separated by finite gaps filled with elastic material 22,49,[55][56][57] . The chains are initially aligned parallel to each other, but otherwise placed in a random non-overlapping way 53 .…”

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confidence: 99%

Tailoring superelasticity of soft magnetic materials

Cremer

Löwen

Menzel

2015

Applied Physics Letters

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Embedding magnetic colloidal particles in an elastic polymer matrix leads to smart soft materials that can reversibly be addressed from outside by external magnetic fields. We discover a pronounced nonlinear superelastic stress-strain behavior of such materials using numerical simulations. This behavior results from a combination of two stress-induced mechanisms: a detachment mechanism of embedded particle aggregates as well as a reorientation mechanism of magnetic moments. The superelastic regime can be reversibly tuned or even be switched on and off by external magnetic fields and thus be tailored during operation. Similarities to the superelastic behavior of shape-memory alloys suggest analogous applications, with the additional benefit of reversible switchability and a higher biocompatibility of soft materials.The term "superelasticity" expresses the capability of certain materials to perform huge elastic deformations that are completely reversible 1,2 . It was initially introduced in the context of shape-memory alloys 3-5 . These metallic materials can perform large recoverable deformations due to stress-induced phase transitions. A transition to a more elongated lattice structure accommodates an externally imposed extension. Typically, this transition shows up as a pronounced "plateau-like" regime on the corresponding stress-strain curve. On this plateau, the samples are heterogeneous with domains of already transitioned material. Then, only relatively small additional stress induces a huge additional deformation. Smart material properties are observed 6-9 : upon stress release, shape-memory alloys can reversibly find back to their initial state. They self-reliantly adapt their appearance to changed environmental conditions.In the present letter, we demonstrate that an analogous phenomenological behavior can be realized for a very different class of materials, exploiting different underlying mechanisms. Moreover, we show that during operation the behavior can be reversibly tailored from outside by external magnetic fields. All of this is achieved by employing soft magnetic gels as working materials: colloidal magnetic particles embedded in a possibly swollen elastic polymer matrix 10 . Similarly to magnetic fluids 11-18 , magnetic gels allow to reversibly adjust their material properties by external magnetic fields. In this way, switching the elastic properties 19-23 offers a route to construct readily tunable dampers 24 or vibration absorbers 25 , while the possibility to switch the shape 19,26-28 allows application as soft actuators [29][30][31] . Here, we show that magnetic gels due to the interplay between magnetic and elastic interactions likewise feature superelastic behavior: it is enabled by a detachment mechanism of embedded magnetic particle aggregates and by a reorientation mechanism of magnetic moments. Both mechanisms are stress-induced and rea) Electronic mail: pcremer@thphy.uni-duesseldorf.de b) Electronic mail: menzel@thphy.uni-duesseldorf.de spond to external magnetic fields. Therefore, su...

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confidence: 99%

Tailoring superelasticity of soft magnetic materials

Cremer

Löwen

Menzel

2015

Applied Physics Letters

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“…In this way, relative strains are introduced as a new macroscopic variable. They complement two previous hydrodynamic concepts introduced in different contexts: on the one hand relative translations, applied in the context of incommensurate smectic phases and chiral smectic polymers [30,31]; on the other hand relative rotations, introduced to characterize nematic and cholesteric liquid crystalline elastomers [32][33][34][35], the rheology of smectic liquid crystals [36][37][38], uniaxial magnetic gels [39,40], ferronematic and ferrocholesteric elastomers [41,42], and the behavior of active components in a gellike environment [43]. Relative translations and rotations have their meaning also in the present context, so we will include them into our approach.…”

Section: Introductionmentioning

confidence: 97%

“…(76) we infer one important difference between the new macroscopic variables of relative strains and the previously introduced variables of relative translations [30,31] and relative rotations [32][33][34][35][36][37][38][39][40][41][42][43]. In the latter cases, only the relative translations and relative rotations between the two components cost energy.…”

Section: Relative Strainsmentioning

confidence: 99%

Hydrodynamic description of elastic or viscoelastic composite materials: Relative strains as macroscopic variables

Menzel

2016

Phys. Rev. E

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One possibility to adjust material properties to a specific need is to embed units of one substance into a matrix of another substance. Even materials that are readily tunable during operation can be generated in this way. In (visco)elastic substances, both the matrix material as well as the inclusions and/or their immediate environment can be dynamically deformed. If the typical dynamic response time of the inclusions and their surroundings approach the macroscopic response time, their deformation processes need to be included into a dynamic macroscopic characterization. Along these lines, we present a hydrodynamic description of (visco)elastic composite materials. For this purpose, additional strain variables reflect the state of the inclusions and their immediate environment. These additional strain variables in general are not set by a coarse-grained macroscopic displacement field. Apart from that, during our derivation, we also include the macroscopic variables of relative translations and relative rotations that were previously introduced in different contexts. As a central point, our approach reveals and classifies the importance of a new macroscopic variable: relative strains. We analyze two simplified minimal example geometries as an illustration.

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“…In order to predict the properties of macroscopic samples, it is necessary to subject our discrete model to some "homogenization". Several approaches of that kind were developed recently [13,14,15]. However, as our model takes into account only a single geometry-axially symmetrical layout of the particles with respect to the external magnetic field-in here we restrict our consideration by a very simple averaging procedure.…”

Section: Homogenizationmentioning

confidence: 99%

Elastic properties of magnetorheological elastomer: description with the two-particle mesoscopic model

Biller

Столбов

Raǐkher

2017

IOP Conf. Ser.: Mater. Sci. Eng.

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View the article online for updates and enhancements. Abstract. A pair of magnetizable solid particles embedded in a cylinder made of highelasticity material is considered as a model of a mesoscopic structure element of a magnetorheological elastomer. An applied magnetic field induces ponderomotive interaction of the particles making them to move relative to one another so as to balance the counteracting magnetic and elastic forces. In a certain parameter range, the system exhibits bistability due to which under the increase / decrease of the field, the interparticle distance changes in a hysteretic manner. This behavior has a significant effect on the ability of the mesoscopic element to resist external load. Using the developed two-particle model prone to the magnetomechanical hysteresis, we extend it to the case of a virtually macroscopic sample presenting the latter as a superposition of such elements with distributed interparticle distances. In spite of its simplicity, this scheme in a generally correct way describes the field-induced changes of the internal structure and elastic modulus of the magnetorheological composites. IntroductionMagnetorheological elastomers (MREs) are a special type of smart composites distinguished by their ability for significant shape and elastic properties changes in response to applied magnetic field. Under magnetization, the microparticles of the ferromagnet filler are got coupled by ponderomotive forces that entails a number of interesting effects: magnetically induced deformation and stiffening of MREs, the magnetic shape memory, and others, all of which possessing a substantial practical potential. At the qualitative level, the picture is simple. The applied external field magnetizes the particles and imparts magnetic moments to them. The arising ponderomotive interaction strives to arrange the particles into a spatial structure that corresponds to the minimum of magnetostatic energy. For the particles embedded in a polymer, this tendency is opposed by the elastic restoring forces, which turn up in the MRE matrix as soon as any particle shifts from its initial position. Both experiment [1,2,3] and theory [4,5,6] show that such changes can strongly modify the properties of simulated MRE samples, thus entailing their qualitatively different behavior. The key issue underlying these peculiarities is the magneto-elastic interaction of the particles in a magnetorheological elastomer at the mesoscopic level, i.e., at the scale of the particle size and the interparticle distance.

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Bridging from particle to macroscopic scales in uniaxial magnetic gels

Cited by 39 publications

References 74 publications

Tailoring superelasticity of soft magnetic materials

Tailoring superelasticity of soft magnetic materials

Hydrodynamic description of elastic or viscoelastic composite materials: Relative strains as macroscopic variables

Elastic properties of magnetorheological elastomer: description with the two-particle mesoscopic model

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