Free Vibration Analysis of Doubly Curved Composite Sandwich Panels with Variable Thickness

In this research, the free vibration analysis of doubly curved composite sandwich panels with variable thickness is studied using higher order sandwich panel theory. For the first time, considering different radii of curvatures of the face sheets in this paper, the thickness of the core is a function of plane coordinates (x,y). In addition, in the current model, the continuity conditions of the transverse shear stress, transverse normal stress and transverse normal stress gradient at the layer interfaces, as well as the conditions of zero transverse shear stresses on the upper and lower surfaces of the sandwich panel are satisfied, which is unique. The formulation is based on an enhanced higher order sandwich panel theory and the vertical displacement component of the face sheets is assumed as a quadratic one, while a cubic pattern is used for the in-plane displacement components of the face sheets and the all displacement components of the core. The equations of motion and boundary conditions are derived using the Hamilton principle. The effects of some important parameters including composite layup sequences, length to width ratio, varying properties of the face sheets materials, Face sheet thicknesses ratio and varying materials of the face sheets were investigated. The results are validated by the latest results published in the literature.