Large Magnetostriction in Epoxy-Bonded Terfenol-D Continuous-Fiber Composite With [112] Crystallographic Orientation

A Terfenol-D continuous-fiber composite with a preferred [112] crystallographic orientation was fabricated by embedding 50-vol% [112]-oriented Terfenol-D continuous fibers of 45 mm long and 1 mm wide in an epoxy matrix, and its magnetic and magnetostrictive properties were evaluated as a function of magnetic field. A [112]-oriented short-fiber composite with reduced Terfenol-D fiber lengths of 4 mm and a randomly oriented particulate composite with irregularly shaped Terfenol-D particles of 10–300 μm size, both with 50-vol% Terfenol-D, were also prepared and characterized for comparison with the continuous-fiber composite and monolithic Terfenol-D. The continuous-fiber composite demonstrated the largest magnetostrictive response with the highest saturation magnetostriction (λS) of 1265 ppm. This λSnot only is 23% and 92% larger than the short-fiber and particulate composites, respectively, but also exceeds the monolithic Terfenol-D by 14%. The higher λS compared to the monolithic Terfenol-D, short-fiber composite, and particulate composite mainly originates from the residual compressive stresses developed in the continuous fibers during epoxy cure, a higher fiber aspect ratio for greater stress transfer from the fibers to the matrix, and texturing of the fibers along the highly magnetostrictive [112] crystallographic axis, respectively.