Research On Nonlinear Static-Dynamic Characteristics And Delamination Growth For Composite Laminated Cylindrical Shells With Delamination

Delamination is a kind of common damage in composite laminated structures. The occurrence of delaminations and their further growth can weaken the stiffness and strength of structure, which will change the structural static and dynamic characteristics. In this dissertation, considering composite laminated cylindrical shells with throughout circumference delamination as the subjects investigated, the static buckling, postbuckling, dynamic stability, nonlinear free vibration, nonlinear dynamic response, as well as the delamination growth of composite laminated cylindrical shells are systematically studied. The research results have an important meaning not only in the academic research but also in the practical engineering. The main research contents are given as follows.Based on the Donnell thin shell theory and the adjacent equilibrium criterion, an analytic model for buckling problems of composite laminated cylindrical shells with throughout circumference delamination is established. And a valid analytic method is sought during solving process. In numerical calculations, three different buckling modals for delaminated shells are presented. Then, the influences of delamination lengths, depths and positions as well as laminate stacking sequences on the buckling loads of delaminated cylindrical shells are discussed in detail. The present results are compared with available data.According to the nonlinear elastic theory, the postbuckling governing equations of delaminated cross-ply cylindrical shells expressed by stress function and deflection are founded and the corresponding boundary conditions, the continuous conditions of displacements and the equilibrium conditions of forces are determined. By employing the Koiter theory and perturbation technique, the asymptotic solutions of governing equations are obtained subsequently. In numerical calculations, the load-deflection curves and the postbuckling deformation curves for delaminated cylindrical shells under axial compression are presented.Based on Rayleigh-Ritz method, an analytic model for dynamic stability of composite laminated cylindrical shells with throughout circumference delamination is established. Firstly, introducing the Heaviside unit step functions and supposing a displacement mode fitting for dynamic problem of delaminated shell, the total energy equation of delaminated cylindrical shell is derived. Then, using double trigonometric series to approximate displacement functions and applying Rayleigh-Ritz method, the Mathieu-type parametric vibrating equations of the system are obtained. And the...