Motivation

Magneto-sensitive elastomers (MSE) are used for numerous technical applications, such as actors, sensors, micro-pumps, and vessels. Typical MSEs consist of a mechanically isotropic elastomer with embedded micron-sized magnetizable particles. In the presence of an external magnetic field, these materials display significant deformations and field-dependent elastic modules. In particular, initially isotropic samples exhibit a pronounced mechanical anisotropy in applied magnetic fields. The magnetically driven switchability of MSEs can be additionally manipulated and crucially enhanced by use of an anisotropic fiber rubber composite in the elastomer matrix.

State of the art and preliminary research

The magneto-mechanical behavior of MSEs has been studied previously, and comprehensive theoretical works are available. The direction and the strength of the magnetically based adaptivity in external field H₀ depends strongly on the sample aspect ratio  in the field direction and on the local arrangement (e.g. chain-like or plane-like) of the magnetizable particles. It was revealed that especially prolate samples containing chain-like particle structures exhibit a strong increment of the mechanical moduli . Depending on the number density and the ratio of chain diameter b versus particle size d_p, MSEs can feature different deformation behaviors, i.e. contraction or expansion. Theoretical approaches predict that considerable effects can be achieved already at moderate field strengths by adjusting the particle arrangement and the sample aspect ratio.

© ISM/IPF

Scientific questions and project objectives

Through specific adjustment of the anisotropic composite properties and the local accumulation of magnetizable particles, the actoric action mechanisms of MSEs in response to a characteristic alignment of the external magnetic field can be manipulated significantly. In close exchange with project TP3, the aim of this project is to model the actoric action mechanisms by describing the interactions at the interface of matrix, filler particles, and fiber on micro scale. Near these interfaces, a localized polymer layer of enhanced stiffness can be assumed. The modeling will be established by means of a microscopic theory, which allows for the derivation of analytical relations for the magnetically induced deformations. Also, it will enable the prediction of the field-dependent elastic modules as a function of temperature (exchange with TP5), matrix anisotropy, cross-linking density, filler concentration, magnitude, and direction of the applied magnetic field.

Contact

Institute of Fluid Mechanics, Faculty of Mechanical Science and Engineering at TU Dresden
Leibniz Institute of Polymer Science Dresden e.V. (IPF)