Free vibration analysis of laminated composites by a nine node iso-parametric plate bending element

Abstract

Composite laminates are being widely used in engineering industry primarily due to their high strength-to-weight ratio. Considerable research has been carried out to understand the static and dynamic behaviour of laminated composite plates. There is much demand for developing efficient finite element codes which can predict the dynamic responses of laminated structures at affordable computational cost. In this paper a nine node isoparametric plate bending element has been used for free vibration analysis of laminated composite plate. The first-order shear deformation theory (FSDT) has been incorporated in the element formulation. Composite plates with different side-to-thickness ratio (a/h), ply orientations and number of layers have been analysed. Based on comparison with literature data, we propose that the present formulation is capable of yielding highly accurate results. Laminated composites with central cut-outs are also studied. Novel data is reported for skew laminated composites. It is found that the natural frequency increases with the increase in skew angle (α) and decreases with increase in aspect ratio (b/a) and thickness (h).