Axial strain of ferrogels under cyclic magnetic fields

Ferrogels are low stiffness polymer materials with embedded magnetic powder filler, giving them the capability to strain in a magnetic field. The large strains, high energy densities and fast responses that have been reported make these materials attractive for actuator applications; however, a full understanding of the dynamic behavior is lacking. This paper presents an experimental study of the cyclic behavior of these materials under various frequencies in both the upright and inverted configurations. A 1D phenomenological magneto-viscoelastic model is developed and used to capture this behavior. The trends in stiffness, viscosity and density are described and then used to predict the amplitude of the strain at different frequencies. (Some figures in this article are in colour only in the electronic version)