[112] oriented Terfenol-D composites

Abstract

This paper describes the manufacture and testing of polymer matrix Terfenol-D particulate composites fabricated with a [112] preferred crystal orientation. The results demonstrate that crystal orientation permits higher saturation strain than previously obtained in particulate composites. Oriented particle composites were fabricated using needle shaped Terfenol-D particulate made from commercially available [112] textured polycrystals. A magnetic field applied during manufacture oriented the particles along their longest dimension. Three materials of 22, 36, and 49% particulate volume fraction, were produced and tested to obtain the magnetostriction at constant mechanical loads from 0.5 to 16 MPa. Results demonstrate that crystallographically oriented particle composites saturate at 1475 microstrain whereas the previous non-oriented particle composite saturates at 1150 microstrain. The authors attribute the increased magnetostriction to a predominance of particle orientation along the [112] crystal direction. Modulus measurements indicate that the composites can be described using an upper bound 1-3 composite model. Upper bound rule of mixtures models show that the 36% and 49% oriented particle composites exhibit 94% and 90% respectively of the predicted upper bound magnetostriction. Further rule of mixtures models are used to illustrate how applied stress increases the effective anisotropy in composites as a function of particulate volume fraction. The results demonstrate that by preferential orientation of particles, Terfenol-D particulate composite materials may be fabricated with magnetostriction properties close to that of bulk Terfenol-D.