Theoretical Modeling of Magneto-active Elastomers: How Mechanical Properties can be tuned by Magnetic Fields

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Contents of the Talk

In recent years, field-controllable functional polymers have gained great scientific and commercial interest due to their highly versatile application possibilities. Most promising is the development towards new energy harvesting technologies, integrated sensors, artificial muscles and soft robotics. The research on such smart and soft materials involves nowadays many different disciplines, ranging from physics and material sciences to computational and applied engineering. A prominent example of field-controllable functional polymers are magneto-active elastomers (MAEs) which feature material properties that can undergo plenty different changes by applying an external magnetic field. The remotely controlled modifications include magnetically induced deformations and actuation stresses, as well as anisotropic enhancement of mechanical moduli up to several orders of magnitude depending on strength, orientation, or modulation of the external magnetic field. MAEs typically represent composite materials, in which magnetic/magnetizable particles are embedded into a soft-elastic polymer network. A general characterization of the material behavior under applied magnetic field is often very challenging. This is due to a strong magneto-mechanical coupling on short and long length scales, resulting in highly involved theoretical modeling. It also appears that the complex linkage of microscopic particle arrangement and macroscopic sample shape in MAEs is responsible for the observed sensitivity to preparation details and experimental conditions. In this talk, a powerful model based on dipole interactions is presented to illustrate various aspects of the intrinsic interplay between equally important macroscopic and microscopic responses to an applied magnetic field. Recently, this model could be employed to describe the effective magnetization behavior on mesoscopic scales. The formulation accounts for the underlying particle distribution and, accordingly, the derived expressions are in general anisotropic. The effective tensor of bulk susceptibility can be implemented in macro-continuum models to achieve an integrated characterization of magnetization fields in real-sized magneto-active composites.