Dynamic magnetomechanical behavior of Terfenol-D/epoxy 1-3 particulate composites

We investigated the dynamic behavior of 1-3 type magnetostrictive particulate composites as a function of both bias field (5-140 kA/m) and frequency (1-100 kHz). The composites consist of approximately 0.5 volume-fraction Terfenol-D particles embedded and magnetically aligned in a passive epoxy matrix. The measured properties include elastic moduli (E-3(H) and E-3(B)), dynamic relative permeability (mu(r33)), dynamic strain coefficient (d(33)), magnetomechanical coupling coefficient (k(33)), and the ratio of the dynamic strain coefficient to the dynamic susceptibility (d(33)/chi(33)). We observed the dependence of these properties on bias field and explain it here in terms of domain-wall motion followed by saturation near 40 kA/m. The spectra of mu(r33), d(33), and d(33)/chi(33) indicate that the magnetization process is independent of frequency and that the effect of eddy-current losses is insignificant up to 100 kHz. The observations agree with predictions made by classical eddy-current theory and suggest that the composites can be operated at significantly higher frequencies than monolithic Terfenol-D.