Free Vibration of Delaminated Composite Timoshenko Beam Considering Poisson's Effect

In this paper, exact solution of free vibration analysis has been established to study the effect of delamination on natural frequencies of thick laminated composite beams. Timoshenko beam theory with various boundary conditions has been employed. The Poisson’s effect is considered in the formulation. Both free and constrained modes have been considered. The influence of the size and location of the delamination on the natural frequencies and mode shapes of a beam are investigated. Studying of mode shapes clarifies the reason of difference of free and constrained modes results, well. The natural frequency shows a high sensitivity for the long and close-to-the-midplane delaminations, but low sensitivity for the others. Considering the Poisson’s effect has almost not influence the cross-ply laminate natural frequencies. But, ignoring it in angle-ply laminates may cause large error. Obtained results are compared with the analytical and experimental data reported in the literature to verify the validity of the present analysis. By considering Poisson’s effect for angle-ply laminates new data has been released.