Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Production and Characterization of Composed-Based Friction Materials for Safety Cluthes in Aviation Applications(01. Izmir Institute of Technology, 2024) Akkurt, Sedat; Akkurt, Sedat; Sütçü, Mücahit; 03.09. Department of Materials Science and Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyDebriyaj 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 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; Demir, Mustafa Muammer; Varlıklı, Canan; 04.04. Department of Photonics; 03.09. Department of Materials Science and Engineering; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of TechnologyColloidal 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.Master Thesis Integration of Red & Blue Tl Materials To Different Polymer End-Use(Izmir Institute of Technology, 2016) İncel, Anıl; Demir, Mustafa Muammer; Demir, Mustafa Muammer; 03.09. Department of Materials Science and Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyTriboluminescence (TL) is known as the emission of light upon the application of any mechanical force. In this master thesis, two organometallic-based TL crystals, which are EuD4TEA and Cu(NCS)(py)2(PPh3) were obtained and they were integrated in the transparent polymers: poly (methylmetacrylate) (PMMA), poly (styrene) (PS), poly (urethane) (PU) and polyvinylidene fluoride (PVDF) for different end-use. In the development of composites, two different processes were carried out: i) embedding (or blending) and ii) surface impregnation. The different end-use polymers were used as transparent polymer film, electrospun nanofibers, and nanobeads. TL performance of composites were investigated by using drop tower system which was specficically designed for this research. Atomic force microscopy (AFM), scanning electron microscopy (SEM) were used to characterize the topographic and morphologic properties of both polymers and composites. Additionally, fluorescence microscopy helped to understand the signal of emitted light by composites. Lastly, piezoelectric properties of composite materials were invetigated by oscilloscope. According to results, type of process, particle size of crystal, surface property and form of host material (polymer), the concentration of crystalline particles in composites were determined as the main parameters and the results were estimated with respect to these parameters. PU-based composite film and fiber show better stability towards mechnical stress rather than PMMA, PS, and PVDF due to the roughness surface of thin-film surface for film-based composites, smallest wickerwork formation of electrospun mats for fiber-based composite, and the chemical affinity of PU with TL crystals.Master Thesis Development of Carbon Black-Layered Clay/Epoxy Nanocomposites(Izmir Institute of Technology, 2008) Pekşen Özer, Bahar Başak; Tanoğlu, Metin; Tanoğlu, Metin; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIn 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, Metin; Tanoğlu, Metin; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyPolymer/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 Investigation of Environmental Durability of Carbon Fiber/Epoxy Composites(Izmir Institute of Technology, 2013) Yağmur, Samet; Tanoğlu, Metin; Tanoğlu, Metin; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyFiber 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 Polyropylene - natural zeolite composite films(01. Izmir Institute of Technology, 1999) Özmıhçı, Filiz; Balköse, Devrim; Özmıhçı, Filiz; Balköse, Devrim; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIn this project, preparation and characterization of polypropylene natural zeolite composites were studied. Three different series of preparation methods were performed, hot press, microscope slide, and extrusion. The composites are ranged between 0-10 wt%, 0-50 wt%, and 0-6 wt% zeolites, for hot press, microscope slide, and extrusion respectively.Polymer matrix composites are materials which contain polymers as matrix materials surrounding very small reinforcing fibers or fillers. Polymeric composites have great potential from a manufacturing standpoint and show advantages. Such as they are inexpensive, derive from natural sources, present lower density than mineral fillers, and increases the mechanical properties of the final product.In this research polypropylene was used as a matrix material and natural zeolite as a filler. Natural zeolite particles were modified with polyethylene glycol to break agglomerates and make a homogenous dispersion of natural zeolite in polypropylene matrix. These composites were characterized by using differential scanning calorimetry, thermal gravimetric analyzer, infrared spectrophotometer, optical microscopy, mechanical testing and by density measurement device. It has been found that, branched shaped air pockets existed in hot pressed and extruded composites. This causes low mechanical strength, and the densities of these films also indicate the presence of voids in the composite.Master Thesis Development of Radar-Absorbing Composite Structures(Izmir Institute of Technology, 2013) Kangal, Serkan; Tanoğlu, Metin; Kangal, Serkan; Tanoğlu, Metin; 03.10. Department of Mechanical Engineering; 01. Izmir Institute of Technology; 03. Faculty of EngineeringRadar 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.Master Thesis Development and Characterization of Light-Weight Armor Materials(Izmir Institute of Technology, 2005) Ünaler, Erol; Tanoğlu, Metin; Tanoğlu, Metin; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIn this study, E-glass/unsaturated polyester composite laminates using woven and non-crimp stitched fabrics and isophtalic and orthophthalic polyester resin were fabricated using RTM (Resin Transfer Molding) technique. In addition to composite laminates, multilayered sandwich laminates using aluminum (Al) plates and alumina (Al2O3) tiles were manufactured to improve the ballistic resistance of the composite structure. An experimental investigation was carried out to determine the mechanical and ballistic performance of E-glass/unsaturated polyester composite laminates with and without aluminum and alumina tiles. The mechanical properties of the composite laminates made with 0/90 woven fabrics and 0/90 and 0/-45/+45/90 non-crimp stitched fabrics and two resin systems were measured for comparison of fabric and resin types. The flexural strength and modulus, compressive strength and modulus through ply-lay up and in plane loading directions, mode I interlaminar fracture toughness and apparent interlaminar shear strength of the composites were measured to evaluate the effects of the fiber architecture on the mechanical properties of the composites. It was found that in general the mechanical properties of the composites made with 0/90 woven fabrics are higher than those of the composites made with multiaxial non-crimp stitched fabrics. Moreover, the composite plates with and without aluminum plates and alumina tiles were subjected to ballistic impact by AP (armor piercing), FSP (fragment simulating projectile) and ball (B) type projectiles with initial velocities in the range of 420-1173 m/s. The ballistic test results exhibit that the polymer composites have ballistic resistance against 7.62 mm fragment simulating projectiles (FSP) up to 1001 m/s projectile velocities. However, the composites without any support layer are not sufficient to stop AP projectiles. The sandwich panels containing ceramic tiles subjected to the ballistic impact by AP and FSP projectiles exhibited only partial penetrations at all the velocities applied within the study (446-1020 m/s with AP and 435-1173 m/s with FSP). The extensions of damages in the composites were evaluated after impact. It is concluded that the multilayered composite structures have capacity against the ballistic threats and potential to be used as lightweight armor materials.Master Thesis Preparation and Characterization of Ha Powders-Dense and Porous Ha Based Composite Materials(01. Izmir Institute of Technology, 2002) Çiftçioğlu, Muhsin; Çiftçioğlu, Muhsin; Şimşek, Deniz; Çiftçioğlu, Muhsin; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe synthesis of hydroxyapatite (HA) powers, whiskers and preparation of HA based ceramics have been investigated in this work. Commercial HA powders were used for comparion purposes. The powder and sintered ceramics were characterized by optical microscopy, SEM,XRD, particle size determination, dilatometry and mechanical testing.Ca-P powders were synthesized by using (NH4)2HPO4 and Ca(NO3)2. 4H2O by aprecipitation method in aqueous medium. Ca/P ratio was set to 1,5 and 1,667 that yield the mixture of Ca-P phases and HA powder respectively at pH 10, 60 C and 24hrs aging. Ca/P ratio was set to 1,667 and the effect of pH of the medium, aging temperature and aging time on the powder characteristics was investigated. pH was set to 4,6,8,9,10 and 11 while aging temperature and time kept constant at 60 C and 24 hrs.Formation of HA powder was observed over pH 8. Agglomerated Monetite-Brushite powder was obtained at pH.4. Monodispersed prismatic Brushite crystals were obtained at pH.6. Aging temperature investigation was performed at 30-90 C at pH.10 for 24 hrs aging. Increase in the aging temperature led to formation of more thermally stable HA phase. Precipitates were aged for 0, 0.5, 1, 24 and 48 hours at constant pH.10 and temperature 60 C. Thermally stable HA phase was obtained over 24hr aging. All of the oven-dried precipitates were heat treated at 400-1250 C range in order to investigate the thermal stability and phase structure development. Optimum conditions for the precipitation of thermally stable HA powder was determined as pH.10, 60 C aging temperature and 24 hrs aging time that yields equaxed HA powder with particle size about 40-60 nm.Molten salt synthesis (MSS) and hydrothermal synthesis (HDT) were used to prepare HA whiskers. XRD patterns of both whiskers have shown that HA was the dominant phase in whiskers and no other phases were detected. Hydrothermal whiskers had submicron diameters with an average aspect ratio of 20. The diameter of the MSS whiskers were in the 1-5 micron range and were mostly hexagonal with an average aspect ratio of 10.10, 20 and 30 vol% whisker containing composites were prepared. Sintering behavior and mechanical properties were investigated. 98% TD of HA ceramics (3.16 g/cm3) was obtained in the 1150-12500C range. 80-90% TD was obtained at above 1200 C for the MSS whisker composites with very little shinkages. Densities of the HDT whisker containing composites were higher than those of the MSS whisker composites. The highest hardness value was determined as 537 Hv for the HA ceramics 1250 C sintered. Hardness of the composites was lower than that of pure HA powder based ceramics due to the presence of relatively high porosity. 10vol% MSS whisker addition yields comparable compressive strength (460-470 MPa) and elastic modulus values (14-17 GPa) with that of natural bone tissues (170-193 MPa compressive strength, 14-18 GPa elastic modulus).