Crystallographically aligned magnetostrictive composites

Abstract

Summary form only given. In this presentation we describe the progress made and the recent discovery at UCLA on magnetostrictive composites. The recent discovery increases the actuation strain of magnetostrictive particulate composites by 50% (i e. 1700 microstrain). The composites are manufactured by combining selected shapes of Terfenol-D particulate with a polymer resin in the presence of a magnetic field. The field aligns the particulates into continuous chains similar to continuous fiber composites (i.e. 1-3 composite). Research on particulate composites has been conducted by a variety of research institutions during the last decade. Previous to this discovery, state of the art in magnetostrictive actuation strain was reported to be 1200 microstrain, achieved at UCLA by maximizing particle packing density. While 1200 microstrain represents a viable actuator, the strain levels were still 50% below those reported for the monolithic material (i.e. 1800 microstrain). During the last year UCLA discovered a new approach based on shape anisotropy that allows crystallographic orientation of the particulate within the magnetostrictive composites. Alignment of selected crystallographic directions produces strain levels comparable to those present in the monolithic material (i.e. 1700 microstrain). A representative figure comparing the response of the monolithic material to a 20% volume fraction particulate composite is provided. Note that the strain outputs from the composite are similar to the monolithic at comparable magnetic field levels. This coupled with the larger frequency response, due to reduced eddy current in the composite, provide a new higher power transducer than currently exists. In this presentation, we will review the progress made at UCLA on these novel actuation systems. This will include detailed information on composite characterization (stiffness, piezomagnetic coefficients, and permeability).