free vibration analysis of composite grid stiffened cylindrical shells using a generalized higher order theory

The present study analyzes the free vibration of multi- layered composite cylindrical shells and perforated composite cylindrical shells via a modified version of reddy’s third-order shear deformation theory (tsdt) under simple support conditions. an advantage of the proposed theory over other high-order theories is the inclusion of the shell section trapezoidal form coefficient term in the displacement field and strain equations to improve the accuracy of results. the non-uniform stiffness and mass distributions across reinforcement ribs and the empty or filled bays between the ribs in perforated shells were addressed via a proper distribution function. for integrated perforated cylindrical shells, the results were validated by comparison to other studies and the numerical results obtained via abaqus. the proposed theory was in good consistency with numerical results and the results of previous studies. it should be noted that the proposed theory was more accurate than tsdt.