Free vibration analysis of sandwich structures with a flexible functionally graded syntactic core

A new model based on high-order sandwich panel theory is implemented to free vibration analysis of sandwich beams with syntactic foam as a functionally graded flexible core. The formulation uses the classical beam theory for the face sheets and an elasticity theory for the FG core. By considering the flexibility of the sandwich core, the model can achieve to high-order effect caused by the nonlinearity of the longitudinal and vertical deformations of the soft FG core. The behavior is presented in terms of internal resultants and displacements in the faces, peeling and shear stresses in the face–core interface and stress and displacement field in the core. A numerical analysis of free vibration of simply supported beams including higher modes that cannot be detected by other models is carried out and a parametric study that investigates the effect of distribution of functionally graded core’s properties is presented.