Multiphysics modeling and simulation of fluid‐saturated porous ferrogels at finite strains

Abstract

Over the last years there has been a growing interest in the study of the behavior of field‐responsive or so called smart materials. Porous ferrogels are a class of these materials consisting of a porous polymeric matrix with dispersed micro‐ or nano‐sized ferromagnetic particles [1–3]. Due to their ability to exhibit large deformations and alter their effective material characteristics upon external magnetic stimulation, these materials are interesting for a wide range of applications in biomedical engineering, microfluidics and other innovative fields of research. The magneto‐poro‐mechanical response of porous ferrogels is a complex phenomenon that spans over multiple length‐scales and essentially depends on (i) the constitutive behavior of the individual components, (ii) their morphology and microstructural arrangement and (iii) the macroscopic shape of the specimen. In this contribution a theoretical and computational framework for the modeling of isotropic porous ferrogels at the macroscale is presented. Within this modeling approach the porous ferrogel is treated as a homogeneous continuum, whereat its complex microstructure is not resolved explicitly. A prototypical isotropic constitutive model is formulated in a conventional enthalpy‐based setting. Numerical examples show the the crucial impact of the macroscopic specimen shape on the macroscopic deformation response in an uniform external magnetic field.

Magneto-Mechanical Coupling in Magneto-Active Elastomers

“…As will be pointed out in the subsequent example, recent findings of the authors show that—on the microstructural level—the effects in MAEs are driven by clusters of interacting particles which are very close to each other. Minimum distances, here 27.5% of the particle diameter, which act as a limit to impede intersecting particles during the random placement algorithm in the geometry generation can, as in this and other examples [ 72 ], entail such an unsystematic behavior, i.e., produce microstructures that are random but apparently not representative. Concerning the missing data points for = 5% as well as = 25% another drawback of the applied modeling strategy in this example can be seen: for increasing magnetic fields, the simple neo-Hookean material model (11c) is not able to resist the attractive forces between close inclusions, see [ 73 ] for further information.…”