Dynamic Response And Buckling Of Composite Cylindrical Shells

Free vibration, nonlinear dynamic response, buckling and postbuckling, delaminarion buckling of composite circular cylindrical shells with stringer and ring stiffeners have been investigated theoretically, numerically, experimentally in this paper. The effects of the shells and stiffener parameters, delaminarion parameters on the stiffened composite shells are discussed. The aim is to provide appropriate analytical methods and theoretical basis for design of stiffened composite shells. The major work in this paper is as follows:At the beginning, the advances in the research of free vibration, nonlinear dynamic response under axial impact load, buckling and postbuckling under axial compression of the stiffened composite shells are reviewed comprehensively. The main comments are systematically remark on the delaminarion buckling. Research background and involved elementary theory of this thesis are emphatically expatiated.The second part of paper is about the analytical solution for the free vibration of simply supported composite circular cylindrical shells with stringer and ring stiffeners. Using the Love's theory and the Rayleigh-Ritz energy method, the frequency equations can be deduced, which can be solved. The effects of shells and orthogonal stiffeners parameters such as the shell thickness-to-radius radio, the shell length-to-radius radio, the stiffener's height, lamination angle and forms on the frequencies are studied. In addition, the effect of hydrostatic pressure is also discussed.The third part presents a simple and efficient semi-analytic method to solve the nonlinear dynamic response of composite circular cylindrical shells with circumferential stiffeners under axial impact load. Applying the discrete stiffened shells model, Based on the composite shell's shear deformation theory, the motion equations of stiffened shells is deduced using Hamilton's variation principle. The deformation of the shells and the load are expanded in double series. The motion equations expressed by deflection are obtained with the Galerkin method, and numerically solved by R-kutta approach. Examples are given for the nonlinear dynamic response of stiffened composite shells under axial impact. The effects of the stiffener geometric parameters, lamination angle, lamination forms, the numbers of lamination layers on the dynamic response of stiffened composite circular cylindrical shells are discussed.In the forth part, the generalized Donnell-type equations governing large deflection of laminated cross-ply circular cylindrical shells based on first-order shear deformation theory are presented. An asymptotic series solution is constructed by the perturbation technique for postbuckling behavior of the cylindrical shell under axial compression. The boundary layer solutions are also designed to match with the out-of-plane boundary conditions by singular perturbation approach, and then determined the critical buckling loads and postbuckling equilibrium paths. The effect s of the stiffener and shell geometric parameters, lamination angle, lamination forms, initial imperfection on the buckling and postbuckling behavior of the shells are discussed.The fifth chapter analyzed the buckling behavior of composite circular cylindrical shells with throughout circumference delamination by using the first first-order shear deformation theory. And establish the buckling model by spaning the entire circumference is divided into multiple sublaminates shell. The deformations are expanded in double series.The variational principle is applied to obtain the governing equations, boundary conditions, the continuous conditions of displacements, the equilibrium conditions of the force and moment. The influences of the shell geometric parameters, lamination angle, lamination forms, length and depth of delamination on buckling load are analyzed.The final part offered an experiment of free vibration, buckling and postbuckling under axial compression of composite circular cylindrical shells with or without delamination. The effects of lamination angle, length and range of delamination on buckling load, postbuckling behavior and the final damage form are discussed. The comparison between the experiment outcome and the numerical results indicates that those frequency results of the composite circular cylindrical shells are in good agreement with each other. However, the result of the crush experiment is inconsistent with the theoretical outcome. At last, the reasons for those discriminations are presented.