Magnetomechanical coupling and elastic moduli of polymer-bonded Terfenol composites

The dependence of coupling coefficient $\mathrm{(k)}$ and elastic moduli ($E_H$ and $E_B$ ) on particle size and volume fraction of Terfenol powder in polymer-bonded composites has been investigated. Materials were prepared with powder in five size ranges between 106 and 710 μm and in three volume fractions ${\mathrm{(V}}_F\mathrm{).}$ The moduli show a $\mathrm{\Delta E}$ effect, which is negative for small bias fields and positive for larger fields. $E_H$ is found to be independent of particle size and to vary with $V_F$ in agreement with model predictions. The maximum value of $\mathrm{k,}$ for each sample, is found to be independent of both particle size and $V_F$ and a simple model is presented which predicts this behavior and indicates that the low values of $k_{\max }$ arise mainly from the low modulus of the epoxy binder.