In this paper, the effect of delamination on free vibration of a simply supported rectangular homogeneous plate with through-width delamination was investigated by the finite strip method. A constrained model was used and a finite strip with bending and in-plane stiffness was derived for the free vibration analysis. The effects of delamination length, delamination location in the thickness-wise and spanwise directions, and aspect ratio of the plate on the natural frequencies of the plate were presented. Results show that the delamination has considerable effect on the natural frequencies of the plate. The aspect ratio of the plate is also having significant effect on the natural frequency of the plate, especially on the mode 2 frequency of the plate.
