The functionally graded layers are inhomogeneous along the thickness direction, while the piezoelectric layer is homogeneous;both possess material orthotropy.

假设上下功能梯度的材料参数沿厚度连续变，则是均匀材料，并且它们都是正交各向异性的。

Complex analysis of anisotropic elasticity indicates that the degree of anisotropy (orthotropy) is characterized by two basic complex parameters.

正交各向异性可以表征复合材料的各向异性特征。