Post-buckling behaviour of metallic skin-stringer assemblies and buckling of composite flat panels

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Havacılık ve Uzay Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2018

Öğrenci: ENES AYDIN

Danışman: ALTAN KAYRAN

Özet:

Stiffened thin panels are very common and important structural elements in aerospace structures because of the weight and stiffness advantages they provide. The stiffener section is important to determine the support condition that the stiffener provides on the unloaded edges of the panel. In the first phase of the thesis study, the effect of the boundary conditions on the buckling coefficients of stiffened metal flat panels is investigated utilizing finite element and empirical approaches. Empirical approaches are limited for panels with classical boundary conditions. On contrary, finite element analysis is more accurate however costly. A database is prepared for the buckling coefficients of the selected skin-stringer combinations by finite element analysis to set up an artificial neural network and response surface for fast calculation of the buckling coefficients of stiffened panels. In the second phase of the study, a comparative study is presented on the post-buckling load redistribution in stiffened panels modeled with and without material nonlinearity. The effective widths of the panel are calculated right before the collapse of the panel using the load distributions determined by the finite element analyses of the panel models with and without material nonlinearity and comparisons are made with the effective width calculated by the classical effective width formulation. In the final phase of the study, composite flat plate buckling is investigated utilizing finite element and analytical approach. A comparison study is done for composite buckling coefficients using various geometric properties of flat panels, boundary conditions, ply thicknesses and orientations. At the end, buckling charts for each ply orientation and boundary conditions are generated utilizing finite element analysis results.