Akademik Veri Yönetim Sistemi
Tezin Türü: Yüksek Lisans
Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Havacılık ve Uzay Mühendisliği Bölümü, Türkiye
Tezin Onay Tarihi: 2014
Öğrenci: SEDAT GÜLDÜ
Danışman: ALTAN KAYRAN
Özet:Automated Fiber Placement (AFP) is a highly automated manufacturing process which has made it possible to manufacture composite parts utilizing curved tow paths resulting in variable stiffness composite structures. During the manufacturing of the composite structures with the automated fiber placement machines, fiber orientation angle can be changed according to the specific design needs. Therefore, variable fiber orientation can be sought in an optimization framework for favorable structural response. The purpose of this thesis is to show how the structural behavior of the cylindrical shell can be improved through the use of fiber placement technology in the manufacturing of the layers of the cylindrical shell of revolution. For this purpose, a methodology is developed for generating the finite element model of tow-placed variable-stiffness laminated composite cylindrical shells. The developed method allows the calculation of the ply thicknesses including the gaps and overlaps which occur as a result of the manufacturing of the plies of the cylindrical shell using curvilinear fiber paths. Fiber orientation angle of each element is determined by making use of the reference fiber path which is defined by two parameters. Along the reference fiber path, fiber orientation angle changes linearly in a specified direction. Finite element model creation and analyses are carried out using the finite element program MSC.NASTRAN®. For the optimization of the reference fiber path, Particle Swarm Optimization (PSO) code is developed in Matlab environment. PSO is a robust optimization technique based on the movement and intelligence of swarms. Optimization of the parameters of the reference fiber path is performed for axially and circumferentially variable stiffness cylinders including the strength and manufacturing constraints. Optimization results are also compared with results of the baseline constant stiffness cylinders. The objective of the optimization is taken as the maximization of the buckling factor of the cylindrical shell subjected to different load cases. Results show that higher buckling load factors can be obtained for variable stiffness cylinders compared to the constant stiffness laminated cylinders.