壓電壓磁纖維複合材料磁電耦合效應之最佳化

Abstract

本論文探討材料極化方向對壓電壓磁纖維複合材料磁電耦合行為之影響，並求得最佳之磁電耦合效應。由於單相多鐵材料的磁電耦合效應微弱，不足以應用在工程上，因此使用雙相或多相壓電壓磁複合材料形式，藉此得到更佳之磁電耦合效應。且由於材料性質會隨著極化方向而改變，所以亦可藉由不同極化方向的組合得到不同的耦合性質，進而得到最佳磁電耦合行為。本論文使用Mori-Tanaka模式與尤拉角轉換之微觀力學模型求得壓電壓磁纖維複合材料之最佳磁電耦合效應並與COMSOL Multiphysics有限元素軟體分析結果相互驗證。 本篇論文發現，對於BaTiO3為內含物、CoFe2O4為母材之複合材料，經由改變材料的極化方向，其最佳化之 與 可分別提升44倍與5倍；對於CoFe2O4為內含物、BaTiO3為母材之複合材料，經由改變材料的極化方向，其最佳化之 與 可分別提升101倍與5倍。

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.