FREE VIBRATION AND BUCKLING CHARACTERISTICS OF FUNCTIONALLY GRADED SANDWICH BEAMS UNDER GENERALLY ELASTIC BOUNDARY CONDITIONS WITH SIX-PARAMETER

The free vibration and buckling characteristics of functionally graded material (FGM) sandwich beams resting on Winkler-Pasternak foundation and under general elastic boundary condition of six-parameter model are investigated by using differential quadrature method (DQM). Sandwich beams are composed of three layers with cores of ceramic material (hardcore), ceramic-metal composites (FGM core) or fully metal material, respectively. Voigt model is employed to describe the effective material properties of FGM layer across the depth of sandwich beams according to mixture power-law distributions. The general elastic boundary conditions at both ends of the beam is simulated by three sets of linear springs. Based on the Timoshenko beam theory, the governing equations and boundary conditions of the static and dynamic model of the system are derived from Hamilton’s principle as a unity. The free vibration responses of FGM sandwich beams are obtained by DQM programming. Based on the duality between the static and dynamic behaviors of the structure, the critical buckling loads are also obtained. The significant influences of stiffness coefficients of boundary spring, ratio of thickness of each layer, sandwich types, material graded index, slenderness ratios and foundation parameters on the free vibration and buckling characteristics of the structure are taken into investigation. Several numerical examples are presented to demonstrate the convergence, reliability and accuracy by using DQM. The decoupling process for static buckling analysis of FGM sandwich beams is distinctly simplified. Moreover, the superiority and universality of the six-parameter beam model are indicated through a comparison with various classical boundary ones.