Master Degree / Yüksek Lisans Tezleri

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

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Access type: Open accessSubject: search.filters.subject.Laminated materials

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Now showing 1 - 5 of 5
  • Master Thesis
    Design of Cnt Fiber Reinforced Laminates for Minimum Weight
    (01. Izmir Institute of Technology, 2024) Karaosmanoğlu, Burhan Burak; Artem, Hatice Seçil
    Kompozit malzemeler günümüzde üretim ve uygulamalardaki yüksek işlevsellikleri nedeniyle birçok alanda yer bulmaktadır. Özellikle, yüksek performans özellikleri kazandırmak amacıyla kompozit güçlendirme malzemesi olarak Karbon Nanotüplerin (CNT) kullanımına olan ilgi giderek artmaktadır. Bu tezde 16 katmanlı, simetrik ve dengeli CNT-fiber takviyeli kompozit laminalar minimum ağırlık tasarımı için incelenmiştir. Yenilik olarak, klasik lamina teorisi dahilinde tanımlanan burkulma problemi bağlamında iki farklı minimum ağırlık tasarım yaklaşımı iki farklı problem altında sunulmuş ve karşılaştırılmıştır. Karşılaştırma kritik burkulma yükü faktörünün ağırlığa oranı şeklinde tanımlanan dizayn verimliği kriteri üzerinden yapılmıştır. Tek ve çok amaçlı genetik algoritmalar kullanılmış; ayrıca tam sayı problemlerine uyarlanmış önerilen bir benzetilmiş tavlama algoritması da test edilmiştir. CNT'lere ek olarak epoksi matris, cam fiber malzemelerinden oluşan laminanın etkin malzeme özellikleri fiber mikromekanik ve Halpin-Tsai modelleri kullanılarak belirlenmiştir. İlk problemde, kritik burkulma yükü faktörünün maksimize edilmesi için çözüme geçmeden önce her bir katmanda CNT ve fiber içerikleri fonksiyonel olarak dağıtılmış, tam sayı fiber açıları ise tasarım değişkenleri olarak alınmıştır. İkinci problemde, kritik burkulma yükü faktörü ve ağırlık çok amaçlı optimizasyon olarak ele alınmış, CNT'lerin ağırlık oranı, fiberlerin hacim oranı ve tam sayı fiber açıları tasarım değişkenleri olarak kullanılmıştır. Sonuç olarak, CNT'lerin ve fiberlerin dağılımının tasarım etkinliğini nasıl etkilediği gösterilmiş ve çok amaçlı optimizasyon yaklaşımın tek amaçlı alternatife kıyasla daha yüksek tasarım verimliliği sağladığı ortaya konulmuştur.
  • Master Thesis
    Vibration Analysis of Laminated Composite Circular Plates With Radial Slots
    (Izmir Institute of Technology, 2014) Baltacı, Çetin Özgür; Yardimoğlu, Bülent
    Vibration characteristics of laminated composite annular circular plates with radial slots are studied by Finite Element Method (FEM). As theoretical background, vibration analysis of orthotropic annular circular plates, mechanics of laminated composites and finite element modeling are summarized. Laminated composite annular circular plates with radial slots are introduced. The APDL program in ANSYS is developed for the titled problem and verified by the available literature for the annular circular plate. Then, the effects of lamination parameters on natural frequencies are investigated.
  • Master Thesis
    Minimum Weight Design of Carbon/Epoxy Laminated Composites for Maximum Buckling Load Using Simulated Annealing Algorithm
    (Izmir Institute of Technology, 2014) Gülmez, Erkut; Artem, Hatice Seçil
    Composite materials have been mostly used in engineering applications such as aerospace, automotive, sports equipment, marine because of their high specific strength-to-weight and stiffness-to-weight ratios. Weight reduction and buckling load capacity are critical issue for the engineering application. Accordingly, in this thesis, identification of optimum fiber orientations and laminate thicknesses of the composite plates resisting to buckling under given loading conditions and aspect ratios are investigated. Furthermore, a comparison study on continuous and conventional designs is performed to determine the effect of stacking sequence on weight. Symmetric and balanced N-layered carbon/epoxy composite plates are considered for optimization process. Critical buckling load factor is taken as objective function and fiber orientations which are considered continuous are taken as design variables. Simulated Annealing (SA) algorithm is specialized by using fmincon as hybrid function and this optimization method is used to obtain the optimum designs. Maximum critical buckling load factor and minimum thickness and hence minimum weight are achieved and shown in tables. As a result, it is observed that loading conditions and plate dimensions play an important role on stacking sequence optimization of lightweight composite laminates for maximum buckling load capacity.
  • Master Thesis
    In-Plane Free Vibration Analysis of Laminated Curved Beams With Variable Curvature
    (Izmir Institute of Technology, 2013) Çangar, Fatma; Yardımoğlu, Bülent
    In this study, in plane free vibration characteristics of laminated curved beams with variable curvatures are studied. The present problem is modeled by differential eigenvalue problem with variable coefficients. FDM (Finite Difference Method) is used to solve the differential eigenvalue problem. A computer program is developed in Mathematica and this program is verified by using results available in the literature. The effects of curvature and lamination parameters of the curved beams on natural frequencies are investigated.
  • 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
    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.