Master Degree / Yüksek Lisans Tezleri

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  • 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
    Production and Characterization of Composed-Based Friction Materials for Safety Cluthes in Aviation Applications
    (01. Izmir Institute of Technology, 2024) Karabulut, Orhan; Akkurt, Sedat; Sütçü, Mücahit
    Debriyaj sistemleri, araç hızını kontrol etmede kritik öneme sahiptir. Bu çalışmada, uçak debriyaj sistemleri, yüzey malzemelerinin kimyasal ve mekanik özellikleri, üretim yöntemleri ve kullanım koşulları incelenmiştir. Ticari kompozit esaslı bir uçak fren balatası (Trimat MN2221) malzeme karakterizasyonu, mikro yapısal (OM, SEM-EDS), faz (XRD), kimyasal (XRF), bağ yapısı (FTIR) ve termal (TGA) analizleri ile gerçekleştirilmiştir. Yeni balata formülasyonları geliştirilmiş ve kompozit balata üretim yöntemleri kullanılarak sabit koşullar altında güvenlik debriyaj balataları üretilmiştir. Farklı katkı maddeleri ve karışım oranları ile deneyler yapılarak balata özelliklerindeki farklılıklar analiz edilmiştir. Bu araştırma, fenolik reçine, kuvars, alümina, cam elyafı ve grafit miktarlarının sürtünme kuvveti ve aşınma direnci üzerindeki etkilerini incelemeyi amaçlamaktadır. Farklı oranlarda alümina (Al2O3) ve kuvars (SiO2) içeren üç farklı debriyaj balatası örneği üretilmiş ve sürtünme özellikleri test edilmiştir. Benzer deneyler, fenolik reçine, cam elyafı ve grafit miktarları değiştirilerek tekrar edilmiştir. SAE J661 standardına göre sürtünme-aşınma testleri yapılmış, yoğunluk, yüzey pürüzlülüğü ve sertlik gibi fiziksel özellikler değerlendirilmiştir. Yoğunluk kütle-hacim ilişkisine göre hesaplanmış, sertlik SHORE D cihazı ile ölçülmüştür. TSE 555 standardına göre spesifik aşınma oranları belirlenmiştir. Sonuçlar, alüminanın sürtünme malzemelerini ve debriyaj performansını artırdığını, kuvarsın ise sürtünme katsayısını iyileştirdiğini göstermiştir. Çalışma, debriyaj performansı için en uygun formülasyon ve optimum üretim parametrelerini belirlemiştir.
  • Master Thesis
    Investigation of the Mechanical and Physical Properties of Barium Glass and Zirconia Nanoparticle Filled Resin-Based Dental Composites
    (01. Izmir Institute of Technology, 2024) Çerci, Nazife; Tanoğlu, Metin
    Geleneksel olarak diş dolgularında kullanılan amalgamlar, büyük ölçüde içerdikleri cıva nedeniyle bir dizi ciddi sağlık sorununa neden olmaktadır. Ayrıca dişin rengine uymayan amalgam dolgular estetiği de olumsuz etkilemektedir. Öte yandan, diş rengiyle uyumu, yüksek mekanik özellikleri, yüksek radyopasitesi, düşük polimerizasyon büzülmesi ve uygulama kolaylığı nedeniyle iyi bir estetik görünüme sahip olan reçine bazlı dental kompozitlerin geliştirilmesi, diş hekimliğinde amalgam dolgulara tercih edilen alternatif haline gelmiştir. Bu tezde, farklı konsantrasyonlardaki (ağ.%) zirkonya ve baryum cam nanopartiküllerinin reçine esaslı kompozitin mekanik ve fiziksel özellikleri üzerindeki etkileri incelenmiştir. Kompozitlerin toplam dolgu maddesi konsantrasyonu ağ.% 65'tir. Kompozitler, sırasıyla ağ.% 40, ağ.% 30 ve ağ.%30 Bis-GMA, UDMA ve TEGDMA içeren bir monomer karışımında ağ.% 20 ve ağ.% 30 yüzey modifiye baryum camı, ağ.% 1 ve ağ.% 2 yüzey modifiye zirkonya nanopartiküllerinin dağıtılmasıyla hazırlanmıştır. Reçine esaslı kompozitlerin mekanik özellikleri; eğilme mukavemeti ve basınç mukavemeti, kürlenme derinliği, polimerizasyon büzülmesi ve su sorpsiyonu ve çözünürlüğü incelenmiştir. Kompozitlerin kırılma yüzeyi taramalı elektron mikroskobu (SEM) kullanılarak incelenmiştir. Üç nokta eğme ve sıkıştırma testi sonuçları, baryum camı ve zirkonya nanopartiküllerinin kompozitlerin mekanik özelliklerini belirgin şekilde geliştirdiğini göstermiştir. ağ.% 30 baryum camı ve ağ.% 1 zirkonya içeren Ba30Z1 numunesi, referans numuneye göre %37'lik bir artışla 79,09 ± 3,32 MPa ile en yüksek eğilme dayanımına ulaşmıştır. ağ.% 20 baryum camı ve ağ.% 2 zirkonya içeren Ba20Z2 numunesi, referans numuneye göre %41'lik bir artışla 250,05 ± 8,01 MPa ile en yüksek basınç dayanımına ulaşmıştır.
  • Master Thesis
    Investigating the Filament Wound Hybrid Cylindrical Structures With Enhanced Thermal Properties by Numerical Analysis
    (01. Izmir Institute of Technology, 2023) Özkan, Mert; Tanoğlu, Metin
    The filament winding method is a composite production technique found at the beginning of the 20th century. The technique has been used in different fields since the day it was introduced in literature. Today, with the developments in the continuous fiber structure used in this technique and the development of carbon technology, filament-wound composites are widely used in the automotive, aerospace, and defense industries. In this study, the finite element method was used to model filament-wound composite cylinders. It was wanted to observe the matrix effect of the composite structure numerically and criticize experimentally produced composites. Even though the current studies work on a hybridized composite structure with respect to the fiber, this study tried to find the hybridized matrix effect by numerical analysis. For this purpose, in this study, the finite element program ANSYS was used. In order to make realistic calculations with ANSYS, material data were observed from composite plates. Finite element models created with the obtained data were compared with the experimental results. The analysis results were observed with the help of the first-ply failure theory. In addition, since the pattern representations from the winding poles cannot be displayed in ANSYS, the pattern effect was ignored, and comparison were made with the assumption of a full layer at given angles. As a result of all this study, although there were differences between experimental and finite element methods' models in homogeneity and pattern, methods' comparisons gave consistent and close results.
  • Master Thesis
    Analysis of Adhesively Bonded Composite Aerospace Structures Developed by Laser Surface Treatment
    (01. Izmir Institute of Technology, 2023) Nuhoğlu, Kaan; Tanoğlu, Metin
    Among the various joining techniques, adhesive bonding is a feasible alternative to mechanical fasteners to prevent incisions and discontinuity on aerospace structures. The performance of the bonded structures highly depends on the adhesion strength, which is directly related to the condition of the bonding surface. It is for this that laser surface treatment, a recently developing technique to improve bonding performance, has become suited for CFRP structures. Yet, predicting the failure strength and mechanism is vital for designing primary aircraft structures involving adhesively bonded composite structures. The scope of this paper consists of the validation and evaluation of adhesive bonding behavior in the case of joining between laser surface-treated CFRP structures, in particular, components of an aircraft wing box. To this end, both the experiment and numerical investigations of the secondary bonded coupons were examined. This study, in other words, includes experimentally revealing the bonding behavior through coupon and element-level mechanical test setups, as well as the simulation of those structures in the computer environment by performing FEA to predict the failure load and damage growth. In this regard, besides observing the effects of the laser surface treatment on the pure and mix-mode behaviors by means of the DCB, ENF, SLJ, and SSJ tests, identical specimens were numerically analyzed by utilizing macro-scale 2D and 3D models, employing the CZM technique. Meanwhile, a novel characterization study and the resulting TSL parameter identification method were achieved for an accurate numerical analysis. Eventually, in addition to the application methodology, the capabilities and appropriateness of the presented FEA method were discussed, comparing experimental and numerical results.
  • Master Thesis
    Development and Experimental Characterization of Filament Wound Hybrid Cylindrical Structures With Enhanced Thermal Properties
    (01. Izmir Institute of Technology, 2023) Özarslan, Dora; Tanoğlu, Metin
    Composite tube components have key roles in many industrial applications, such as pipelines, drive shafts, airplane fuselages, and offshore construction components. Filament winding technology has enabled precise tailoring and manufacturing processes, allowing for a variety of applications to be manufactured with advanced machinery. In this study, the aim was to enhance the thermal properties without any significant change in the mechanical properties. Therefore, the samples were manufactured as carbon fiber composite tubes with different resin layer configurations by utilizing filament winding technology. The fiber orientation was set to a 55° winding angle with a 5/3 pattern to wrap over a 58.8 mm diameter mandrel as a 5-layer stacking. Due to difficulties in manufacturing different stacked groups of phenolin resin layers, only two groups (one with a 5-layer carbon epoxy resin group and one with a 4-layer carbon epoxy resin with 1 outer layer of carbon phenolin resin group) were successfully manufactured and thus tested. For each group, with dimensions of ±62.7 mm outer diameter and ±1.95 mm thickness with an 800 mm length, two composite tubes were manufactured. Before the test procedures, the homogeneity and quality of the groups were analyzed. For the observation of properties, mechanical and thermal tests were conducted: Apparent hoop tensile, radial compression, 3-point bending, Flammability, Thermogravimetric analysis, Differential scanning calorimeter, Thermal conductivity. The tests were proceeded according to their standards. The results and failure behaviors demonstrate that, with the replacement of the outer layer with phenolin resin, no significant improvement or drawback was observed compared to its fully epoxy resin counterpart.
  • Master Thesis
    A Numerical Approach for Optimization of Curing Kinetics of Composite Material
    (Izmir Institute of Technology, 2021) Öz, Murat; Tanoğlu, Gamze
    In this thesis, we introduced a new method which is called the GMN (Gamze, Murat, Neslişah) algorithm. GMN algorithm determines the pre-exponential and activation energy of the curing process. This algorithm include tanh fitting for the measured conversion values via least squares minimization technique and linear fitting for the kinetic parameters. Experimentally determined differential scanning calorimetry (DSC) data sets for an epoxy resin functionalized by single wall carbon nanotubes are used for the verification of the proposed method. In computational part, in order to denote the effectiveness of the new proposed method, the results are also compared with the methods reported in the literature. To sum up, we have shown that the GMN algorithm provides a good match with the experimental data for all kinetic parameters.
  • Master Thesis
    Stacking Sequences Optimization of Laminated Composites for Maximum Buckling Strength by Stochastic Search Methods
    (Izmir Institute of Technology, 2020) Adabaşı, Gökay; Artem, Hatice Seçil
    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
    Development of Fiber Reinforced Cylindrical Composite Structures by Filament Winding Technique
    (Izmir Institute of Technology, 2019) Aydın, Mustafa; Tanoğlu, Metin
    Fiber reinforced composite structures with superior properties are used for cylindrical structure systems in many application areas nowadays. The major aim of this thesis is development of filament wound composite cylindrical structures with various fiber types on different ply sequence and investigate their mechanical properties. For this purpose, 4 layered glass, carbon and glass/carbon hybrid fiber reinforced cylindrical structures were manufactured with 55 degree winding angle by utilizing filament winding technique. Produced 6 different composite structures have 1 m length and 60 mm inner diameter. Glass/carbon fiber reinforced systems were developed to reduce the cost by reducing carbon fiber usage. Apparent hoop tensile strength and radial compression tests were applied to the manufactured composite structures. In addition to these studies, two different composite plate with glass fiber and carbon fiber reinforcements were produced by filament winding to investigate glass transition temperature. These plates were manufactured with 4 layered by using the same fiber and matrix as used in the previous tube production. Dynamic mechanical analysis was performed with samples which is sectioned from plates to obtain glass transition temperature. Consequently, apparent hoop tensile strength test results showed that hoop strength of glass fiber reinforced cylindrical structures can be improved significantly by hybridization. Based on the radial compression test results, deflection of the structures decreases by hybridization
  • Master Thesis
    Fabrication of Colloidal Photonic Crystals Via Langmuir Blodgett Technique and Their Integration of Polymer Matrix
    (Izmir Institute of Technology, 2019) İnci, Ezgi; Demir, Mustafa Muammer; Varlıklı, Canan
    Colloidal films have potential uses in various fields such as photonics, electronics, sensors, membrane filters, and surface devices owing to their unique optical properties. Photonic crystals composed of uniform diameter colloidal silica particles have been arranged in a periodic structure by taking inspiration from nature. The periodic structure of silica particles has physical interaction with light in a visible range. This special interaction is known as structural coloration. The close-packed monolayers and multilayers of colloidal silica particles in large area can be produced by using Langmuir Blodgett method. The integration of these photonic films with transparent polymer matrices having an elastomer feature provides for their use in optical sensor applications. In this thesis, we examined the fabrication of mechano-sensitive nanostructured films based on colloidal particles. Silica colloidal particles were synthesized at different sizes by using Stöber Process. Langmuir-Blodgett deposition was used to create three-layer of photonic crystal films with different particle diameters. For this purpose, various substrates were examined for the Langmuir Blodgett deposition process before starting the coating. The coated silica particles on the glass substrate were then embedded in an elastomeric transparent matrix. The generation of structural coloration after stretching was examined in manufactured elastomer films. In accordance with this purpose, various polymers such as acrylates and siloxanes with elastomer properties have been used. The structural characterization of these composite films and their optical properties were summarized in this thesis.