Nonlinear behavior of magnetostrictive particle actuated composite materials

A new theory is presented for the nonlinear multiaxial magnetoelastic behavior of magnetostrictive particle actuated composite materials. The analysis assumes a uniform external magnetic field is operating on a large number of well-distributed, crystallographically and shape parallel ellipsoidal magnetostrictive particles encased in an elastic, nonmagnetic composite matrix. The aspect ratio of the particulates may vary between 1 and infinity and the volume fraction of the particulates may vary between zero and one. Comparisons between experimental and model magnetostriction results show that the model is able to provide a quantitatively correct dependence on particulate volume fraction and longitudinal stress and quantitatively accurate magnetostriction curves for both homogenous Terfenol-D rod and magnetically ordered Terfenol-D particulate actuated epoxy matrix composites over experimental applied field ranges. Model calculations clearly indicate that the particle actuated composites developed less longitudinal strain than would be expected from the behavior of the homogeneous material.