This paper introduces a comprehensive investigation of bi-directional functionally graded sandwich plates using higher-order shear deformation theory and finite element method for the first time. A special procedure incorporating with a bi-linear four-node quadrilateral element is used to treat the free condition of shear stresses on two surfaces of the sandwich plates. Four types of the bi-directional functionally graded sandwich plates with several thickness ratios of layers are considered, in which the material properties of the layers are assumed to vary in both the thickness and the in-plane directions. The present results are compared with published data in some special cases to demonstrate the convergence and accuracy of the present algorithm. The investigations show that the variation of the material ingredients and properties, the boundary conditions, the thickness ratio of layers play significant roles on the bending, free vibration and buckling behaviors of bi-directional functionally graded sandwich plates.
