Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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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, MetinGeleneksel 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, MetinThe 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, MetinAmong 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, MetinComposite 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 Development of Fiber Reinforced Cylindrical Composite Structures by Filament Winding Technique(Izmir Institute of Technology, 2019) Aydın, Mustafa; Tanoğlu, MetinFiber 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 hybridizationMaster Thesis Development of Carbon Black-Layered Clay/Epoxy Nanocomposites(Izmir Institute of Technology, 2008) Pekşen Özer, Bahar Başak; Tanoğlu, Metin; Tanoğlu, MetinIn this study, a novel epoxy nanocomposite with electrical conductivity and having improved mechanical and thermal properties was synthesized. Carbon black/ epoxy composites and carbon black-layered clay/epoxy nanocomposites were prepared by mixing via 3-roll mill. The first type of the composite was produced to determine the percolation threshold concentration (Vc). The second type with constant carbon black concentration, slightly over Vc, was synthesized to investigate the influence of clay content on the thermal, mechanical, electrical and structural properties of nanocomposites. Carbon black used in the study was extra conductive filler with 30 nm spherical particles. Layered clay was Na+ Montmorillonite treated with ditallow dimethlyamine to assure better intercalation within the epoxy resin. Vc value was determined to be 0.2 vol% and 0.25 vol% carbon black was added together with varying clay contents to the epoxy system to produce nanocomposites. Only the nanocomposites with 0.5 vol. % clay loading showed electrical conductivity. However, the composites with higher clay loadings showed insulating behaviour due to hindrance of carbon black network by clay layers. According to the XRD results, nanocomposites exhibited some extent of exfoliation. It was found that tensile modulus values of the epoxy increased;however flexural modulus values remained constant, with increasing clay content.Elastic modulus of neat epoxy (3.7 GPa) was increased about 28 % with 0.5 vol% clay addition. Thermomechanical analysis results revealed that the storage modulus, glass transition temperature and initial degradation temperature of epoxy was slightly enhanced due to clay loading.Master Thesis Preparation and Physical Characterization of Clay/Epdm Nanocomposites(Izmir Institute of Technology, 2008) Karşal, Çiçek; Tanoğlu, MetinPolymer/clay nanocomposites have been extensively studied in recent years because they often exhibit improved properties different from their micro and macrocomposite counterparts. Addition of organophilic layered silicates to the polymer produces effective polymer nanocomposites by intercalation of macromolecules into the interlayer spaces. The performance of polymer/clay composites is not only related to the nature of the clay but also to the reinforcing mechanism of filler and the preparation conditions.In this study, the effects of mixing conditions and effect of aging on mechanical,physical and thermal properties of ethylene-propylene-diene rubber (EPDM)/Organo modified montmorillonite (OMMT) nanocomposites were studied at two different clay loadings 5 wt.% and 10 wt.%. EPDM/OMMT nanocomposites were prepared by melt blending method. The experimental results of X-ray diffraction (XRD) and scanning electron microscopy showed that the organically modified MMT existed in the form of an intercalated structure and that was exfoliated in EPDM matrix depending on the mixing conditions. XRD patterns showed that the interlayer distance of the organically modified clay was 30.9A, which was larger than those of the unmodified clay (14.6A).The mechanical evaluation of the nanocomposites was performed by tensile and tear testing. The mechanical tests showed that the properties of nanocomposites were significantly improved with addition of OMMT. The effects of the processing conditions were manifested in both the morphology and mechanical properties, which showed significant increase when optimized process conditions are applied. In addition, chemical test was performed on the nanocomposites to monitor the degradation of the mechanical properties. It was found that the reduction of the mechanical properties of nanocomposites after aging process is lower as compared to those of neat EPDM.Master Thesis Processing and Characterization of High Performance Piping Materials for Geothermal Applications(Izmir Institute of Technology, 2003) Toğulga, Murat; Tanoğlu, MetinPolymer composite based pipes are being recently utilized in transportation of geothermal fluids.The utilization of composites is due to their resistance to aggressive chemicals and hot-wet environment with relatively high specific strength and design flexibility.Exposure of materials to wide range of temperatures and humidity level, while under the action of load, may degrade them and cause to severe reduction in their properties and service life.Understanding the complex degradation mechanism of the composites exposed to a variety of temperature and fluid chemistry (including geothermal fluid) is essential to improve their durability.This research focuses on the investigation of interactions between geothermal fluid and composite piping materials made of various matrices and the mechanism of degradation in these composites.The matrix materials include polyester, epoxy and graphite particle added epoxy materials.In this study, E-glass fiber reinforced polymer composites were fabricated by employing filament winding and tube rolling techniques.Fabricated composites and neat polymers were exposed to dry environment, distilled water and geothermal fluid of Balçova geothermal field until the saturation of weight gains due to water uptakes.In addition, the specimens with neat polymers were prepared to simulate and follow the degradation of matrix materials under hot-wet environments.Once the saturation occurred, the specimens were subjected compressive mechanical testing.For both dry and wet specimens, the mechanical testing was performed to obtain stress-strain behavior, modulus of elasticity, strain at failure values and energy absorption during the loading.The results were compared to evaluate the degradation of the properties due to various exposures.Moreover, the thermal conductivity of the various composites fabricated in this research was measured to determine the heat losses and temperature distribution within the materials.The temperature distribution within the cross-section of the pipes for various materials was analyzed using a finite element-modeling tool, LUSAS for uninsulated pipes.The heat loss occurring during the transportation of hot geothermal fluid was calculated as a case study to compare composites and traditional metal piping.It was found that polyester composite pipes have higher mechanical performance under axial and radial compression as compared to the composite with epoxy matrices. For all the composite types, some considerable degradations were measured due to exposure to hot-wet environments.The extend of degradation was less for graphite particles added epoxy composite pipes that exhibited the lowest water uptake values. The graphite particles incorporated into the matrix affected the water uptake and thermal conductivity of the epoxy.The water uptake of polyester matrix composite pipes was the highest that might be related to the most extensive degradation of polyester based composite.Moreover, it was found that the thermal conductivity of the composites is much lower than traditional materials.The graphite particles cause reduction in thermal conductivity, simultaneously in heat loss for uninsulated pipes.However, if the isolation is used, heat loss is not sensitive to pipe material.Master Thesis Investigation of Environmental Durability of Carbon Fiber/Epoxy Composites(Izmir Institute of Technology, 2013) Yağmur, Samet; Tanoğlu, MetinFiber reinforced polymer composites, that have increasing demand in many applications such as aircraft and automotive industry, are usually exposed to different environmental conditions which may be harmful to them. The investigation of their environmental durability is critical for those applications. The objective of this study was to investigate the effects of temperature and moisture on durability of carbon fiber reinforced epoxy composites. For this purpose, 0/90° woven, plain unidirectional and non-crimp biaxial ±45 fabrics were used as reinforcement. The specimens were manufactured using vacuum resin infusion process to obtain relatively high fibre volume fraction ratios. The composites manufactured were exposed to cyclic aging conditions to simulate aircraft flight environment. Hygrothermal, high temperature and freezing conditions were used as in one cycle which was 12 hours long. Moisture absorption was determined by weighing the specimens at regular intervals as a function of aging cycles. Tensile and flexural tests were performed prior to aging and after 500, 1000 and 1500 hours aging. After the completion of aging cycles, the moisture content did not increase significantly due to presence of subzero and high temperatures in aging cycles. The mechanical test results revealed differences based on the fabric types used. It was found that the tensile strength and modulus values of woven composites increased after aging cycles as compared to those of unidirectional and biaxial composites. On the other hand, flexural properties decreased at the end of the aging cycles for the composites aged as test coupons.Master Thesis Development of Radar-Absorbing Composite Structures(Izmir Institute of Technology, 2013) Kangal, Serkan; Tanoğlu, MetinRadar absorbing materials (RAMs) are dielectric or magnetic materials that has capacity for absorbing electromagnetic waves. In order to increase frequency range (bandwidth) of the absorbance, several structures have been already proposed by several researchers. Objective of this study is to design, fabricate and characterize RAMs based on glass fiber reinforced epoxy composites within 2-18 GHz frequency range. For achieving radar wave absorbance, several structures such as Dallenbach layer, Salisbury screen and Jaumann absorber were designed and manufactured from polymeric composites. Glass fiber / epoxy system were employed as a base structure. Carbonyl Iron based powders were used as a filler for electromagnetic wave absorber in epoxy matrix. In Salisbury screens and Jaumann absorbers resistive sheets are used to increase the bandwidth of absorbance. Glass fabric surfaces were cotaed with thin layer of metallica conductor with surface resistances up to 1000 ï — to act as a resistive layers within the composite structure. Coatings were done by a large scale magnetron sputtering unit. Resulting structures achieve 12 dB reflection loss with thicknesses varies from 2.65 to 3.15 mm and the resonant frequency detected as 7 GHz. Since in many applications composites are implemented into vehicles and structures such as aircraft wings and wind turbine blades, the purpose of Radar Absorbing Sturctures (RAS) is not only increase the bandwidth of absorbance, but also to serve as a structural element in which. For this reason, structural and physical performance of RAMs has been one of great importance. In this study, mechanical and thermomechanical properties of developed RAMs were also characterized to evaluate the structural performances. It is observed that, addition of carbonyl iron affected the mechanical properties due to lack of binding with epoxy matrix. This effect can be clearly seen at tensile and impact properties that up to 30% losses were observed.