Poroelasticity in the presence of active fluids

TL;DR

This paper introduces a linear poroelastic model for porous media embedded with magnetorheological fluids, capturing their tunable phase transition effects under magnetic fields, validated through experiments on sponge composites.

Contribution

It develops and validates a simplified poroelastic formulation for active porous media with magnetorheological fluids, enabling design and optimization of adaptive materials.

Findings

Model accurately predicts composite behaviour under magnetic control

Experimental validation confirms the model's robustness

Potential applications include adaptive exosuits and structural systems

Abstract

This work presents a model for characterizing porous, deformable media embedded with magnetorheological fluids (MRFs). These active fluids exhibit tunable mechanical and rheological properties that can be controlled through the application of a magnetic field, which induces a phase transition from a liquid to a solid-like state. This transition profoundly affects both stress transmission and fluid flow within the composite, leading to a behaviour governed by a well-defined threshold that depends on the ratio between the pore size and the characteristic size of clusters of magnetic particles, and can be triggered by adjusting the magnetic field intensity. These effects were confirmed through an experimental campaign conducted on a prototype composite obtained by imbibing a selected MRF into commercial sponges. To design and optimize this new class of materials, a linear poroelastic formulation is proposed and validated through comparison with experimental results. The constitutive relationships, i.e. overall elastic constitutive tensor and permeability, of the model are updated from phenomenological observations, exploiting the experimental data obtained for both the pure fluid and the composite material. The findings demonstrate that the proposed simplified formulation is sufficiently robust to predict and optimize the behaviour of porous media containing MRFs. Such materials hold significant promise for a wide range of engineering applications, including adaptive exosuits for human tissue and joint rehabilitation, as well as innovative structural systems.