A magnetostrictive composite exhibiting strains over 0.6

A novel magnetic wire-filled polymer has been developed for use in high strain magnetostriction technologies. The dependence of the magnetostriction of this composite on the wire volume fraction, wire length, applied dc magnetic field strength, and applied ac magnetic field frequency is reported. The wires are magnetically soft steel, 0.254 mm in diameter, cut to approximately the same length in a given sample, and dispersed with random orientation in a commercially available soft polymer. The wire lengths investigated were 0.50 cm, 0.75 cm, and 1.50 cm with wire volume fractions, or “loadings,” between 0.003 and 0.20. The measured strains were reversible and the sample consisting of 0.50 cm wires with a wire loading of 0.20 exhibited a maximum strain of about 0.6 or 60% in an applied dc magnetic field of 7 kOe. The frequency response of the composite is that of a damped harmonic oscillator with a loading-independent resonant frequency around 40 Hz; the damping and resonant response scaled with wire loading.