Study On Elastic Kinetics Of Layered Composite Magnetoelectric Materials

Magnetoelectric(ME) materials refers to the certain kind of functional materials which can generate induced magnetic moment in external electric field or induced electric moment under an applied magnetic field. It can realize mutual conversion and regulation between magnetic and electrical signals. It has important strategic significance and promising application in the trend of miniaturization in information storage, sensors and so on. Generally the conversion coefficient αE is used to weigh the strength of ME transformation in magnetoelectric materials. Because the natural ME materials are very few and the ME coupling is very weak at room temperature, many kinds of ME composite are emerging.In this paper the bonded bilayer TDF-PZT ME composite is taken as the research object and the specific strains of laminate ME composite in magnetic field are studied through experiments and theoretical analysis based on the theory of elastic mechanics. The specific contents are as follows:1、The various rules of ME effect under different magnetic field for 2-2 bilayer laminate ME composites are analysed in detail based on the theoretical model of Harshe, Bichurin, Nan, Dong and other scholars. But the theoretical values are always greater than the experimental results, and the original interfacial coupling coefficient k which is used to fit the gap between the theoretical values and experimental results shows a little random and lacks of strict theoretical and experimental support. So the difference between original theory and experiment becomes the major researching object of this paper——Saint Venant’s principle and bending.2、The strains of the free ends of ME composite are measured. Considering Saint Venant’s principle and based on the plane stress model, the gradient distribution of inner stress and strain in PE phase is deduced using a series of boundary conditions without bending. From the perspective of local effect the former theoretical model is modified. The derived results confirm that the stress and strain decrease in PE phase with the thickness increasing considering Saint Venant’s principle. This phenomenon results the overall reduction in piezoelectric effect. So the new theoretical model matches the experimental results better than the former one.3、The butterfly shape strains of PE phase show a bending theory of elastic mechanics. The relationships between the angle of bending and the actual shape, Yang’s modulus of composites when bending occurs are deduced. The theoretical simulation matches well with experiment. At the same time the butterfly shape has been successfully imitated based on the theory of electrostrictive equations. The paper explains the mismatch of the former theory from bending.