Finite element analysis of free vibration of delaminated composite plates

Based on the Mindlin plate theory, a finite element formulation is presented for the analysis of the free vibration of composite plates with multiple delaminations. The present formulation includes the effect of transverse shear defomations as well as the bending-extension coupling caused by the presence of delaminations, and can be easily used to compute the natural frequencies and mode shapes of delaminated plates with arbitrary boundary conditions. A variety of examples, including composite plates with multiple elliptical delaminations, are presented. The effects of boundary conditions, delamination size, delamination location and the number of delaminations on the natural frequencies and mode shapes of delaminated composite plates are investigated. The presence of local modes in the delaminated segments is also discussed.