The Magnetoviscoelastic Response of Elastomer Composites Consisting of Ferrous Particles Embedded in a Polymer Matrix

TLDR

Elastomer composites containing carbonyl iron particles form columnar structures that enhance mechanical response to magnetic fields, offering promise for variable‑stiffness devices and adaptive structures. The study examines the mechanical response of elastomer composites to magnetic fields and introduces a quasi‑static dipole model to analyze their magnetoviscoelastic behavior. During curing, a strong magnetic field aligns iron particles into columnar structures, and a semi‑empirical quasi‑static dipole model—adjustable for multipolar interactions—is used to analyze the resulting magnetoviscoelastic behavior. Experiments demonstrate that a 30 % iron‑particle composite can exhibit up to a 0.6 MPa (30–40 %) increase in shear modulus under magnetic fields, and the semi‑empirical dipole model accurately fits this behavior across a broad field range.

Abstract

The mechanical response of elastomer composites to applied magnetic fields is examined. These elastomer composites consist of carbonyl iron particles embedded within a molded elastomer matrix. The composite is subjected to a strong magnetic field during curing, which causes the iron particles to form columnar structures that are parallel to the applied field. This special composite geometry is known to enhance the mechanical response to the application of post-cured magnetic fields. Experimental data is presented that shows that up to a 0.6 MPa change in mechanical shear modulus (which represents 30-40% change in modulus for the materials tested) is possible in response to an applied magnetic field for a composite containing 30% (V/V) iron particles. A simple quasi-static dipole model is presented to examine the magnetoviscoelastic effect of these elastomer composites. The model is semi-empirical in that it may be fit to experimental data over a broad range of applied fields by adjusting a parameter that accounts for unmodeled multipolar magnetic interactions between particles within the composite. Such elastomer composites hold promise in enabling variable stiffness devices and adaptive structures.