Large magnetostrictive response of Terfenol- D resin composites (invited)

In this article we present results for magnetostrictive composites containing between 10% and 50% Terfenol-D (Tb0.3Dy0.7Fe2) in a nonmetallic binder. The composite consists of aligned Terfenol-D particles representative of a [1-3] fiber composite. For this study we measure the modulus of elasticity and other pertinent magnetostrictive properties. The measured stiffness values fall between the upper and lower bounds predicted by a rule of mixtures approximation. The magnetostriction for the composites rival that of the monolithic at comparable magnetic field levels. A mechanically unloaded 20% volume fraction composite produces 900 ppm and a 30% volume fraction composite preloaded with 8 MPa produces 1000 ppm. Contrary to the belief that the greater the magnetostrictive particulate volume, the greater magnetostrictive properties—this study shows that there is an optimal balance of epoxy and magnetostrictive material that will maximize magnetostriction for a mechanically unloaded specimen. For the matrix chosen in this study, the optimal volume fraction is near 20%.