In this work, the modeling of laminated composite and sandwich beams with a generic cross-section is performed through a variable separation approach. For this purpose, the displacement is approximated as a sum of sepa-rated functions of the cross-section coordinates y, z and the axial coordinate x. This choice yields to a non-linear problem that can be solved by an iterative process. This latter consists of solving a 2D and 1D Finite Element problem successively at each iteration. Numerical examples involving several representative sandwich and laminated beams are addressed to show the accuracy of the present method. It is shown that it can provide 3D results and capture local effects for various types of cross-section