Free Vibration Analysis of Delaminated Composite Plate Using 3D Degenerated Element

In this study, a new model for analyzing delaminated plates was developed using three-dimensional (3D) degenerated elements. The elements were developed using the degenerated solid approach based on Reissner-Mindlin assumptions. Thus, the shear deformation and rotary inertia effect were considered, and the 3D field was reduced to a two-dimensional (2D) field in terms of midsurface nodal variables. The delamination was incorporated using Heaviside step functions. The proposed model was found to be very accurate and also faster in comparison with layerwise/higher-order theories. Results for natural frequencies of plates and beams with and without delamination were compared with theoretical and experimental results available in the literature and were in excellent agreement. New results were generated using the proposed method for different boundary conditions, ply orientations, size of delamination, and location of delamination; these will serve as benchmarks for future research.