Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

Browse

Filters

2011 - 201922020 - 20212

Settings

Subject: search.filters.subject.Buckling (Mechanics)

Search Results

Now showing 1 - 4 of 4
  • Master Thesis
    Optimization of Buckling Behavior of Hybrid Composite Beam Under Axial Compression
    (01. Izmir Institute of Technology, 2021) Altıntaş, Hayri; Artem, Hatice Seçil; Artem, Hatice Seçil; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The use of lighter and high-performance materials in the aerospace sector is of great importance. Optimization methods, which have become very popular with the technological development in the production methods of composite structures in recent years and provide the most suitable design for the purpose, are frequently preferred in the design of parts in the aviation industry. Determining the buckling load capacity of a composite beam under compression load is very important for the design of composite structures. The buckling load capacity of a hybrid composite beam with fiber metal laminate (FML), which is frequently used between aircraft wing and fuselage. The optimum design of the anti-buckling behavior of the hybrid composite beam, which is subjected to compression load, fixed by simple support on both sides, was performed by a genetic algorithm (GA) based on the Tsai-Wu fracture criterion. The robust design of composite hybrid laminates was developed using a design optimization process based on GA with the finite element method. A multi-objective genetic algorithm (MOGA) was used to optimize the design of a hybrid composite beam subjected to buckling. Design variables in the optimization process are considered as fiber material and angle orientations. The purpose of the objective function is to reduce the equivalent stress of hybrid composites while increasing critical buckling load. The design constraint was the Tsai-Wu failure index. As a result, it has been observed that the buckling performance of the beam depends on the structure of the metal material in FML composites. Carbon/epoxy and glass/epoxy structures were proposed and a design was aimed according to the maximum buckling load in the best stacking sequence, taking into account the data in the design constraints.
  • Master Thesis
    Stacking Sequences Optimization of Laminated Composites for Maximum Buckling Strength by Stochastic Search Methods
    (Izmir Institute of Technology, 2020) Artem, Hatice Seçil; Adabaşı, Gökay; Artem, Hatice Seçil; 01. Izmir Institute of Technology; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering
    Based on materials developed and made available by humans, there are materials that will serve their purpose. Using lighter materials, especially in the field of aviation and space, significantly reduces the costs. However, lightness is not the only feature required in materials. In addition, the physical and mechanical properties of the materials must be at the desired level. Knowing the buckling load capacity of composite materials, which are widely used, is also very important in determining the material properties. Accordingly, an important focus of this thesis is to examine the behavior of different materials against the same loading; the other is to examine the increase in the critical buckling load factor although they have the same geometric structure. Critical buckling load factor is considered when performing the buckling analysis. The mechanical behavior of composite materials used by considering the factors of critical buckling load factor has been investigated and discussed. Different optimization methods have been used while making the optimum design of different composite materials with 48 and 64 layers in total. The verification of mechanical properties of materials was made with the help of coding. Subsequently, the referenced articles were verified to prove the accuracy of this code. Optimization was carried out by using material properties information from reference articles and verifying the code. As a result, considering the buckling strength of different layered composite materials, it has been found that the optimum designs depend on the load, load ratio, and plate aspect ratio.
  • Master Thesis
    Optimum Design of Anti-Buckling Behaviour of the Laminated Composites Considering Puck Failure Criterion by Genetic Algorithm
    (Izmir Institute of Technology, 2011) Deveci, Hamza Arda; Artem, Hatice Seçil; Artem, Hatice Seçil; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    In recent years, fiber-reinforced composite materials have been increasingly used in engineering applications due to their advantages such as strength and weight reduction. Determination of the buckling load capacity of a composite plate under in-plane compressive loads is crucial for the design of composite structures. Accordingly, in this thesis, optimum designs of anti-buckling behavior of 64-layered carbon/epoxy composite plates, which are simply supported on four sides and subject to biaxial compressive in-plane loads, are investigated considering Puck failure criterion by using genetic algorithm (GA). The plates are taken to be symmetric and balanced with continuous fiber angles in the laminate sequences. Critical buckling load factor is taken as objective function and fiber orientations are taken as design variables. The critical buckling load factor is maximized for various loading cases and plate aspect ratios. The optimum designs obtained are controlled layer by layer using Puck failure criterion. A comparison between continuous and discrete plate (laminate in which the orientation angles are limited to the conventional orientations) designs is performed in order to show the reliability of continuous plates. The optimization of 48-layered composite plates has been performed in order to be compared with 64-layered composite plates. The optimum designs considering Puck inter-fiber failure mode C has also been investigated. Finally, a comparative study between Puck and Tsai-Wu failure criteria is performed and the advantage of Puck failure criterion is shown. In conclusion, it is found that the optimum designs of laminated composites considering buckling and ply failure strength depend on loading, loading ratio and plate aspect ratio.
  • Master Thesis
    Stacking Sequences Optimization of the Anti-Buckled Laminated Composites Considering Various Failure Criteria
    (Izmir Institute of Technology, 2011) Söyleyici, Mehmet Umut; Artem, Hatice Seçil; Artem, Hatice Seçil; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    In recent years, fiber-reinforced composite materials have been mostly used in engineering applications due to advantage of the ratio of strength to weight. Fiberreinforced laminated composites with an optimum stacking sequences have become critical issue especially for defence and automotive industry. In this study, stacking sequences optimization of laminated composites for maximum buckling load factor has been investigated using genetic algorithm (GA). Symmetrical and balanced laminated composite plates with 48 layers graphite/epoxy are considered for optimization process. The designs of composite plates have been investigated for various in-plane loadings and aspect ratios. Fiber orientation angles are chosen as design variables. The optimum designs obtained have been controlled by Tsai-Wu and maximum stress failure criteria. Furthermore, dispersed designs for specific cases have been converted to conventional designs and the advantages and disadvantages of various designs have been examined in terms of buckling resistance. Finally, buckling behaviors of 48- and 64-layered composite plates have been studied under overloaded conditions. In design process, the increase in the reliability of the optimization has been provided independently using a variety of genetic algorithm parameters. All the results have shown that the loading conditions and dimensions of composite plates are significant in stacking sequences optimization of laminated composite materials in terms of maximum critical buckling load factor. Furthermore, it has been seen that the fiber orientation angles determine which failure modes (buckling or static failure criteria) are critical.