Rayleigh's formalism is generalized for the evaluation of the effective material properties in multicoated circular fibrous multiferroic composites. The derived solution is applied to the special three-phase composite in which coated fibers are embedded in a matrix. For composites made of piezoelectric (BaTiO 3) and piezomagnetic (CoFe 2 O 4 or Terfenol-D) phases, we find that the magnetoelectric effect in the composite made of CoFe 2 O 4 coated BaTiO 3 in matrix Terfenol-D is five times larger than that in the composite made of BaTiO 3 coated Terfenol-D in matrix CoFe 2 O 4. Furthermore, in each case, with appropriate coating to the circular fiber, the magnetoelectric effect in the coated composites can be enhanced by more than one order of magnitude as compared to the corresponding noncoating composite. V

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Magnetoelectric coupling is of interest for a variety of applications, but is weak in monolithic materials. Strain-coupled bilayers or multilayers of piezoelectric and magnetostrictive material are an attractive way of obtaining enhanced effective magnetoelectricity. This paper studies the optimization of magnetoelectricity with respect to the crystallographic orientations and the relative thickness of the two materials. We show that the effective transverse (α E,31) and longitudinal (α E,33) coupling constants can be enhanced many-fold at the optimal orientation compared to those at normal orientation. For example, we show that the constants are 17 and 7 times larger for the optimal orientation of a lithium niobate/Terfenol-D bilayer of equal thickness compared to the normal orientation. The coupling also increases as the piezoelectric phase gets thinner.

This paper studies the effective behavior of piezoelectric and piezomagnetic circular fibrous composites with imperfect interfaces under longitudinal shear with in-plane electromagnetic fields. Two kinds of imperfect contact are investigated: mechanically stiff and dielectrically/magnetically highly conducting interfaces, and mechanically compliant and dielectrically/magnetically weakly conducting interfaces. For the former case, the potential field is continuous, while the normal component of the flux undergoes a discontinuity across the interface. For the latter case, the normal component of the flux is continuous, while there is a jump of potential field at such a contact. The classic work of Rayleigh (1892 Phil. Mag. 34 481-502) in a periodic conductive perfect composite is generalized to the current coupled magnetoelectroelastic composites with imperfect interfaces. It is shown that the expression of the effective property has exactly the same form as that in the ideal coupling composite. Finally, this method is used to study BaTiO 3-CoFe 2 O 4 composites and provide insights into enhancing the effective magnetoelectric voltage coefficient by properly choosing the interface.

We study the macroscopic behaviors of multilayered multiferroic composites with interface imperfections by a direct micromechanical approach. Both generalized interface stress type and generalized linear spring type imperfect interfaces are considered. Concise matrix expressions of the overall behaviors of the layered piezoelectric–piezomagnetic composite with contact imperfection are presented. The key step is to observe that the two types of imperfect interface conditions are equivalent to the perfect ones due to the laminated geometry. Numerical calculations are demonstrated for BaTiO3–CoFe2O4 multilayer media, and are shown in good agreement with the more involved interphase model. Furthermore, it is observed that the interface imperfection would reduce the magnitude of the magnetoelectric voltage coefficients as compared to the corresponding perfect interface case. This feature is opposite to that predicted and observed in the corresponding cylindrical composites.