| Summary: | 碩士 === 國立交通大學 === 土木工程學系 === 99 === Magnetoelectric effects refer to the polarization induced by a magnetic field or the magnetization induced by an electric field. However, magnetoelectric coupling is weak in single phase materials. Composite materials, on the other hand, are an alternative to improve the magnetoelectric coupling. In this work, we optimize the effective magnetoelectric voltage coefficient of fibrous composites made of piezoelectric and piezomagnetic materials. The optimization of magneotelectricity is with respect to the crystallographic orientations and the volume fraction for the two
materials. We use Mori-Tanaka micromechanical model, Euler angle transformation, and finite element analysis (COMSOL Multiphysics) to estimate macroscopic properties of the composites.
We show that the effective in-plane ( ) and out-of-plane ( ) coupling coefficients can be enhanced many-fold at the optimal orientation compared to those at normal orientation. For example, we show that the constants are 44 and 5 times larger for the optimal orientation of barium titanate fibers in a cobalt ferrite matrix of the optimized volume fraction compared to the normal orientation, while they are 101 and 5 times larger for cobalt ferrite fibers in a barium titanate matrix.
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