Free vibration of laminated composite and sandwich plates using global–local higher-order theory

In this paper the global–local higher-order theory is used to study the free vibration of laminated composite and sandwich plates. This global–local theory can satisfy the free surface conditions and the geometric and stress continuity conditions at interfaces, and the number of unknowns is independent of the layer numbers of the laminate. Based on the higher-order theory, a refined three-noded triangular element satisfying C1 weak-continuity conditions is presented. For general laminated composite plates, results obtained from present global–local higher-order theory have been found in good agreement with those obtained from three-dimensional elasticity theories. Moreover, this theory is still suitable for analysis of laminated plates with arbitrary layouts and soft-core sandwich plates whereas numerical results show that the global higher-order and first-order theory overestimate natural frequency for these special structures. This theory cannot only calculate the natural frequencies but can accurately predict the modal stress distributions in the thickness direction without any smooth techniques.