Laminated composite rectangular and annular plates: A GDQ solution for static analysis with a posteriori shear and normal stress recovery

The Generalized Differential Quadrature (GDQ) Method is applied to study laminated composite degenerate shell panels such as rectangular and annular plates. The theoretical treatment is maintained general in order to expose in a unique way the procedure adopted to obtain the stress profiles through the thickness of plates without specifying the equations for rectangular and annular plates. By simply imposing some geometrical relations the equations governing the problem of plates under consideration, that are degenerate shells, are inferred from the theory of shells of revolution. The mechanical model is based on the so called First-order Shear Deformation Theory (FSDT) deduced from the three-dimensional theory in order to analyse the above moderately thick structural elements. The solution is given in terms of generalized displacement components of points lying on the middle surface of the plate. After the solution of the fundamental system of equations in terms of displacements and rotations, the generalized strains and stress resultants are evaluated by applying the Differential Quadrature rule to the generalized displacements. The transverse shear and normal stress profiles through the laminate thickness are reconstructed a posteriori by using local three-dimensional elasticity equilibrium equations. No preliminary recovery or regularization procedure on the extensional and flexural strain fields is needed when the Differential Quadrature technique is used. By using GDQ procedure through the thickness, the reconstruction procedure needs only to be corrected to properly account for the boundary equilibrium conditions. In order to verify the accuracy of the present method, GDQ results are compared with the ones obtained with semianalytical formulations and with 3D finite element methods. Stresses of several composite plates are evaluated. Very good agreement is observed without using mixed formulations and higher order kinematical models. Various examples of stress profiles for rectangular and annular plate elements are presented to illustrate the validity and the accuracy of GDQ method