DFG Priority Program 1713

P3 Magneto-sensitive elastomers

Prof. Dr.-Ing. habil. Markus Kästner	PD Dr. Marina Grenzer
markus.kaestner@tu-dresden.de	grenzer@ipfdd.de

Dipl.-Ing. Philipp Metsch	Dr. Dirk Romeis
philipp.metsch@tu-dresden.de	romeis@ipfdd.de

Field-controllable functional polymers represent a relatively new class of applied materials exhibiting a strong coupling of mechanical and external fields. The application of such fields influences the interactions between different local material phases and causes an evolution of the microstructure.

A prominent example are magneto-sensitive elastomers (MSEs) featuring mechanical moduli that become enhanced under an applied magnetic field as well as the ability for magnetically induced deformations and actuation stresses. This makes MSEs very attractive for a variety of technical implementations, especially for actoric applications such as artificial muscles, sensors, micro-robots and micro-pumps. Since the effective coupled magneto-mechanical behavior is of special interest in these applications, an in-depth understanding of the structure-property relations in MSEs as well as suitable theories for computing the effective macroscopic material response are required.

MSEs represent a two-component system, in which micron-sized magnetizable particles are embedded in a soft polymer network. The flexibility of polymer sub-chains between cross-links allows a considerable degree of particle movement and even diffusion under strong magnetic fields. As a result, the particles are prone to organize themselves into chain-like microstructures, which may considerably influence the coupled magneto-mechanical properties of MSEs.

In this joint project, two work groups from the Leibniz-Institute for Polymer Research Dresden (IPF) and the Institute of Solid Mechanics of TU Dresden (IFKM) develop adapted modeling and simulation techniques to capture the hierarchical material structure, to simulate its evolution and to predict the resulting macroscopic, strongly coupled magneto-mechanical material behavior of MSEs. Analytical and numerical models representing the local material structure and the coupled material behavior will simultaneously be considered at IPF and IFKM to predict the complex structure-property interactions. In a joint approach to efficiently account for the magnetically driven evolution of the heterogeneous material structure, e.g. resulting from the migration of particles in weakly cross-linked polymers, the developed methods are combined with a phase-field model which implicitly represents the features and the evolution of the local material structure. It is expected that the development of this model will benefit from knowledge and related approaches within SPP 1713.

The theoretical predictions for magnetostriction and mechanical moduli for different lattices and realistic particle distributions as well as regarding the influence of the field-induced evolving local material structure will be compared among the work groups and with existing literature results. The results will then be validated by comparison with experimental studies on the influence of magnetically induced evolution of particle microstructures on the properties of MSEs.