چكيده به لاتين
In this thesis, the buckling and post buckling behaviors of composite plates with circular cut out using classical theory with cross ply symmetric laminate have been studied. Implementation of semi analytical, semi energy method on composite plates with circular cut out in the middle of the plate is the main innovation of this research. The effects of using corresponding Airy stress function in the buckling and post buckling analyses of the composite plates having circular cut out are included in this innovation. At first, buckling and post buckling behavior of composite plates with circular cut out is analyzed based on the semi analytical energy method. Then, in order to postpone those behaviors, that multilayer composite is studied using longitudinal, planar, and ring stiffeners based on the semi analytical, semi energy, numerical, and experimental methods. In this study, at first, the finite element method is used to validate this research results. Then, the needed variables to modeling the composite plates having internal circular cut out are obtained using the standard experiments. Besides, some models with and without stiffener with specified dimensions were tested. The finite element method and the experimental results show the accuracy of this study analyses. Besides, the results indicate that the semi energy method is more accurate than the full energy one in predicting buckling and post buckling behaviors. The results of this study shows tolerated load due to pressure displacement is the most for longitudinal, planar, and ring stiffener, respectively.
Besides, buckling of a plate with circular cut out is analyzed based on semi energy and full energy methods in the presence of corresponding plate stress field and without this stress field. In the full energy method, the stress distribution is considered fixed at the plate. In order to buckling study based on the semi energy method, the Airy stress function of a plate with circular cut out is obtained according to existing stress conditions of the plate, at first. Then, the plate buckling is obtained based on Airy stress function and using eigenvalue analysis. The results show the semi energy method considering stress field has the acceptable accuracy.
