Coupling effect of finite magneto-electric laminate composites

The topic of this dissertation focuses on the manufacturing, testing, and modeling magneto-electric laminate composites (MELC). MELC consists of layered magnetostrictive and piezoelectric materials that produces coupling between magnetization and polarization using mechanical transmission. Magneto-electric materials have been proposed for a wide range of applications including magneto-electric transducers, storage devices and electromagnetic devices. However, the coupling present in current M-E materials is too weak and requires improvements furthermore, the lack of precise models hinders the accurate prediction of MELC responses. The purpose of this dissertation is to develop both models and an understanding so as to improve the M-E responses.Theoretical models are first developed for six configurations including three field orientations, longitudinal, transverse, and in-plane, in both 1-D and 2-D geometries without considering end effects. By analyzing these models, results show that higher magnetostrictive compliance causes a decrease in the M-E effect while a larger piezomagnetic coefficient ratio q33/q31 changes the sequencing and higher piezomagnetic coefficient only increases the magnitude of M-E effect. By summarizing these results from the models, a 3-D M-E sequencing map spanning compliance, Poisson's ratio, and q33/ q31 of the magnetostrictive phases is generated to maximize the M-E coupling.The end effects produced in the finite samples are next evaluated to understand the M-E behaviors strain variation in the sample and the effective M-E voltage coefficient a&d1 as a function of bias magnetic field Hbias. A comparison of analytical modeling and experimental tests are conducted for the MELC with a total of three different piezoelectric volume fractions of 0.17, 0.29 and 0.44. Analytical modeling incorporating shear lag and demagnetization effects shows substantial strain decay near the free ends while demagnetizing effect additionally decreases the far-field strain values. By using a longer sample with a thinner and stiffer bonding layer, the shear lag effects can be reduced. When a magnetostrictive layer with smaller relative permeability values and higher aspect ratio (i.e. longer length) is used, the demagnetization becomes less significant. The analytical predictions agree with the experimental results well within 5% for all samples. This demonstrates that shear lag and demagnetizing effects must be considered for the finite MELC.