Browsing by Author "Tanoğlu, Metin"

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Analysis of adhesively bonded composite aerospace structures developed by laser surface treatment
(01. Izmir Institute of Technology, 2023-06) Nuhoğlu, Kaan; Tanoğlu, Metin; 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.
Citation Count: 0
Analysis of adhesively bonded joints of laser surface treated composite primary components of aircraft structures
(Elsevier Sci Ltd, 2023) Nuhoglu, Kaan; Aktas, Engin; Tanoglu, Metin; Martin, Seckin; Iplikci, Hande; Barisik, Murat; Iris, Mehmet Erdem; Tanoğlu, Metin
The performance of the adhesively bonded aerospace structures highly depends on the adhesion strength between the adhesive and adherents, which is affected by, in particular, the condition of the bonding surface. Among the various surface treatment methods, as state of the art, laser surface treatment is a suitable option for the CFRP composite structures to enhance the adhesion performance, adjusting the roughness and surface free energy with relatively minimizing the damage to the fibers. The aim of this study is the validation and evaluation of the adhesive bonding behavior of the laser surface-treated CFRP composite structures, using the finite element technique to perform a conservative prediction of the failure load and damage growth. Such objectives were achieved by executing both experimental and numerical analyses of the secondary bonded CFRP parts using a structural adhesive. In this regard, to complement physical experiments by means of numerical simulation, macro-scale 3D FEA of adhesively bonded Single Lap Joint and Skin-Spar Joint specimens has been developed employing the Cohesive Zone Model (CZM) technique in order to simulate bonding behavior in composite structures especially skin-spar relation in the aircraft wing-box.
Citation Count: 24
Characterization investigations during mechanical alloying and sintering of W-20 vol% SiC composites
(Elsevier Science Sa, 2010) Coskun, Selim; Ovecoglu, M. Lutfi; Ozkal, Burak; Tanoglu, Metin; Tanoğlu, Metin
The effect of mechanical alloying and the sintering regime on the microstructural and the physical properties of W-SiC composites were investigated. Powder mixtures of W-20 vol.% SiC were mechanically alloyed (MA'd) using a Spex mill for 3 h, 6 h and 24 h. MA'd powders were characterized by Laser Diffraction Particle Size Analyzer, SEM and XRD investigations. MA'd W-20 vol.% SiC powder composites were sintered under inert Ar and reducing H-2 gas conditions at 1680 degrees C and 1770 degrees C for 1 h. The microstructural and mechanical characterizations of the sintered samples were carried out by scanning electron microscope (SEM) and X-ray diffraction (XRD) and Vickers Hardness analyses. The addition of SiC remarkably increases the hardness of the composites. Hardness is also increased with decreasing grain size and increasing amount of MA. (C) 2009 Elsevier B.V. All rights reserved.
Citation Count: 81
Critical aspects related to processing of carbon nano tube/unsaturated thermoset polyester nanocomposites
(Pergamon-elsevier Science Ltd, 2007) Seyhan, A. Tugrul; Gojny, Florian H.; Tanoglu, Metin; Schulte, Karl; Tanoğlu, Metin
Carbon nanotubes (CNTs) have outstanding mechanical, thermal and electrical properties. As a result, particular interest has been recently given in exploiting these properties by incorporating carbon nanotubes into some form of matrix. Although unsaturated polyesters with styrene have widespread use in the industrial applications, surprisingly there is no study in the literature about CNT/thermoset polyester nanocomposite systems. In the present paper, we underline some important issues and limitations during the processing of unsaturated polyester resins with different types of carbon nanotubes. In that manner, 3-roll mill and sonication techniques were comparatively evaluated to process nanocomposites made of CNTs with and without amine (NH2) functional groups and polyesters. It was found that styrene evaporation from the polyester resin system was a critical issue for nanocomposite processing. Rheological behaviour of the suspensions containing CNTs and tensile strengths of their resulting nanocomposites were characterized. CNT/polyester suspensions exhibited a shear thinning behaviour, while polyester resin blends act as a Newtonian fluid. It was also found that nanotubes with amine functional groups have better tensile strength, as compared to those with untreated CNTs. Transmission electron microscopy (TEM) was also employed to reveal the degree of dispersion of CNTs in the matrix. (c) 2006 Elsevier Ltd. All rights reserved.
Design of composite-based leaf spring systems for automotive sector
(Izmir Institute of Technology, 2013-12) Öztoprak, Nahit; Tanoğlu, Metin; Tanoğlu, Metin
The applications of fiber reinforced polymeric composites in several engineering fields such as automotive, aviation, defense industry and marine are observed vastly nowadays. Especially in the automotive industry, the necessity of the reduction of fuel consumption and CO2 emission has entailed the utilization of the composite materials to provide weight reduction without sacrificing any material strength. Conventional steel leaf springs are components significantly affecting the weight of the vehicle as well as providing ride comfort and vehicle stability. Hence, fiber reinforced polymeric composites having many outstanding properties such as low density, high strength, corrosion resistance, high fatigue life, high wear resistance, are convenient materials for these types of applications. In this thesis, three different composite-based mono leaf springs were designed and analyzed. It was inferred from the analyses that 0Â° unidirectional glass fiber system hasnâ€™t generated the intended spring rate accurately. Consequently, alternating configurations of the glass and carbon hybrid systems were studied. It was deduced from the studies that material configuration of [0Â°6G/0Â°2C/0Â°22G]S was generated the intended spring rate. Three different composite-based mono leaf springs including indicated material configurations were fabricated within the thesis study. Manufactured prototypes were also tested by using leaf spring test rig for determining the behavior of the prototypes experimentally. The obtained results were compared with FEA and it has been observed that the results are in compliance.
Desing and production of light-weight pressure resistant composite tank materials and systems for hydrogen storage
(Izmir Institute of Technology, 2020-07) Kartav, Osman; Tanoğlu, Metin; Tanoğlu, Metin
This thesis focuses on the development of high-pressure resistant composite tanks for hydrogen storage. For this aim, composite tanks with aluminum liners were designed and manufactured by filament winding technique with various lay-up configurations and tested. The main objective of this study was to develop composite tanks with 700 bar working pressure and 1400 bar burst pressure. Furthermore, composite doily layers were incorporated into the filament winding technique and inserted at the front and end dome sections of the composite tanks to improve the burst pressure performance of the composite tanks and to develop the manufacturing process. Before the manufacturing process, the winding simulations were completed using CADWINDTM CAM software. The manufactured composite tanks were hydrostatically loaded with increasing internal pressure up to the burst pressure. During loading, the deformations over the composite tanks and liners were measured locally using strain gauges. Besides, composite plates were manufactured by filament winding technique to determine the mechanical and the thermo-mechanical properties, and the fiber mass fractions of composite sections were determined. Additionally, a preliminary study was carried out to investigate the effect of hybrid fiber usage on the burst pressure performance of steel liner based composite tanks. The effect of filament winding parameters on the burst pressure performance of composite tanks was investigated experimentally. The aimed burst pressure value of more than 1400 bar was obtained in this study for aluminum liner-based carbon fiber reinforced composite tanks. Also, a desired safe burst mode that is expected to occur in the mid-region of the composite tanks was successfully obtained. This study may be useful for the development of composite tanks for high-pressure hydrogen storage especially for the automotive industry and can be helpful to decrease the usage of fossil fuels.
Citation Count: 0
Determination of activation energy for carbon/epoxy prepregs containing carbon nanotubes by differential scanning calorimetry
(Sage Publications Ltd, 2023) Uz, Yusuf Can; Tanoglu, Metin; Tanoğlu, Metin
The aim of the present study is the thermal characterization of laboratory-scale carbon fiber/epoxy-based prepregs by incorporating single-wall carbon nanotubes (SWCNTs). Investigation of the cure behavior of a prepreg system is crucial for the characterization and optimization of the fiber reinforced polymeric (FRP) composite. To affect dispersion characteristics, SWCNTs were functionalized by oxidizing their surface with carboxyl (-COOH) group using an acid treatment. The modified resin system contained 0.05, 0.1, and 0.2 wt. % functionalized SWCNTs (F-SWCNTs). Carbon fiber (CF) reinforced prepregs containing various amount of F-SWCNTs were prepared using drum-type winding technique. FTIR was performed to identify new bonding groups formed after the functionalization of SWCNTs. Cure kinetics of prepregs prepared with/without F-SWCNTs were investigated using isoconversional methods.
Citation Count: 9
Developing polymer composite-based leaf spring systems for automotive industry
(Walter de Gruyter Gmbh, 2018) Oztoprak, Nahit; Gunes, Mehmet Deniz; Tanoglu, Metin; Aktas, Engin; Egilmez, Oguz Ozgur; Senocak, Ciler; Kulac, Gediz; Tanoğlu, Metin
Composite-based mono-leaf spring systems were designed and manufactured to replace existing mono-leaf metal leaf spring in a light commercial vehicle. In this study, experimentally obtained mechanical properties of different fiber-reinforced polymer materials are presented first, followed by the description of the finite element analytical model created in Abaqus 6.12-1 (Dassault Systemes Simulia Corp., RI, US) using the obtained properties. The results from the finite element analysis are presented next and compared with actual size experimental tests conducted on manufactured prototypes. The results demonstrated that the reinforcement type and orientation dramatically influenced the spring rate. The prototypes showed significant weight reduction of about 80% with improved mechanical properties. The hybrid composite systems can be utilized for composite-based leaf springs with considerable mechanical performance.
Citation Count: 8
Development and analysis of composite overwrapped pressure vessels for hydrogen storage
(Sage Publications Ltd, 2021) Kartav, Osman; Kangal, Serkan; Yuceturk, Kutay; Tanoglu, Metin; Aktas, Engin; Artem, H. Secil; Tanoğlu, Metin
In this study, composite overwrapped pressure vessels (COPVs) for high-pressure hydrogen storage were designed, modeled by finite element (FE) method, manufactured by filament winding technique and tested for burst pressure. Aluminum 6061-T6 was selected as a metallic liner material. Epoxy impregnated carbon filaments were overwrapped over the liner with a winding angle of +/- 14 degrees to obtain fully overwrapped composite reinforced vessels with non-identical front and back dome layers. The COPVs were loaded with increasing internal pressure up to the burst pressure level. During loading, deformation of the vessels was measured locally with strain gauges. The mechanical performances of COPVs designed with various number of helical, hoop and doily layers were investigated by both experimental and numerical methods. In numerical method, FE analysis containing a simple progressive damage model available in ANSYS software package for the composite section was performed. The results revealed that the FE model provides a good correlation as compared to experimental strain results for the developed COPVs. The burst pressure test results showed that integration of doily layers to the filament winding process resulted with an improvement of the COPVs performance.
Development and characterization of innovative fiber reinforced prepregs and their composites containing functional fillers
(Izmir Institute of Technology, 2021-07) Uz, Yusuf Can; Tanoğlu, Metin; Tanoğlu, Metin; Izmir Institute of Technology
This Ph.D. thesis aims to prepare laboratory-scale carbon fiber reinforced prepregs and improve the performance of their composites by incorporating functionalized single-wall carbon nanotubes (SWCNTs). The effect of nano-scale functional fillers on the characterization of prepregs and their composites was investigated to develop innovative materials for primary structures. To affect dispersion characteristics, SWCNTs were functionalized by oxidizing their surface with the carboxyl (-COOH) group using acid treatment. The modified resin system containing 0.05, 0.1, and 0.2 wt. % F-SWCNTs were developed with novel multi-step dispersion techniques. FTIR spectroscopy was performed to identify new bonding groups formed after the covalent functionalization. Unidirectional carbon fiber reinforced prepregs with/without F-SWCNTs were prepared using a drum-type winding technique by utilizing the solvent-dip (solution impregnation) process. The effect of F‐SWCNTs on the curing process and kinetic parameters of the carbon fiber/epoxy-based prepregs were investigated using non‐isothermal DSC. The activation energy of the curing reaction was calculated by the isoconversional methods. Also, the new numerical approach called GMN was developed to determine the activation energy of the thermosetting materials. For the fabrication of prepreg-based composite laminates, the vacuum bag-only (VBO) method was performed. The fiber volume fractions of the CFRP samples changed between 55.3% and 50.16%. The mechanical and thermomechanical properties of prepreg-based CFRP composites with/without F-SWCNTs were investigated. The optimum mechanical properties of F-SWCNTs filled CFRP composite was achieved at 0.05 wt.% of F-SWCNTs. However, mechanical properties were decreased due to the addition of higher content of F-SWCNTs, in comparison with neat CFRP.
Development and characterization of light-weight armor materials
(Izmir Institute of Technology, 2005) Ünaler, Erol; Tanoğlu, Metin; Tanoğlu, Metin
In 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.
Development and characterization of PMMA based porous materials used for high pressure casting of sanitaryware ceramics
(Izmir Institute of Technology, 2004) Ergün, Yelda; Tanoğlu, Metin; Tanoğlu, Metin
The ceramic whiteware / sanitaryware industry is rapidly undergoing to implement high-pressure casting techniques for ceramic article production. In high pressure technique, porous materials with open cell microstructure that allow drainage of water from the ceramic suspension under applied pressure are needed. In addition, a relatively high mechanical performance of the porous structure is required to obtain a long service life from the material under the cycled high pressures. The polymethyl methacrylate (PMMA) based polymeric porous structures have become the most suitable type of materials for this purpose because of their short casting periods and high service lives. The superior service life and performance of these materials are closely related to their microstructure. In the present study, PMMA-based porous materials were produced by water-in-oil emulsion polymerization technique. The porous systems were produced with various compositions of the constituents in the emulsion and various filler sizes to investigate the effect of the constituents and the sizes on the microstructure of PMMA-based materials. The variations on the pore microstructure were related to the performance of the material. The pore morphology and porosity of the samples was investigated using optical and scanning electron microscopy techniques (SEM). Water permeability was measured using a custom made permeability apparatus. The mechanical properties such as compressive collapse stress and elastic modulus values were determined by performing mechanical compression tests. It was found that increasing water surfactant concentration increases the porosity, water permeability and decreases mechanical properties and reversely increasing the amount of monomer in the emulsion decreases the porosity, water permeability and increases the mechanical properties. Fracture toughness values of the materials were measured by using single edge notch three point bending (SENB) test method. Fracture toughness test results and fracture surface analysis show that materials are fractured in brittle manner. It was found that lower concentrations of water and higher concentrations of monomer result in thicker cell walls and improve the fracture toughness of the material. To investigate the residual mechanical properties, specimens were subjected to cyclic loadings. After cyclic loading, increase of elastic modulus with the percentage of 52 and decrease of collapse stress values were measured.
Development and experimental characterization of filament wound hybrid cylindrical structures with enhanced thermal properties
(01. Izmir Institute of Technology, 2023-06) Özarslan, Dora; Tanoğlu, Metin; 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.
Development and mechanical characterization of anti-blast sandwich composites for explosive effect
(Izmir Institute of Technology, 2011) Baştürk, Suat Bahar; Tanoğlu, Metin
Composite sandwich structures have high potential to be used in anti-blast armour systems due to their lightweight and resistance to explosive effects. This study focuses on the production and mechanical characterization of sandwich structures with aluminium (Al) foams of various thicknesses in conjunction with skins composed of Al/GFPP fibre/metal laminates. The bonding between the components of the sandwich was achieved by various surface modification techniques such as silane surface treatment, polypropylene (PP) adhesive film addition and their combination. The Al sheet/Al foam sandwiches were also prepared to investigate the effect of GFPP addition on the performance of sandwich structures. The energy absorption capacities together with compressive and flexural behaviour of both Al foams and FML/Al foam sandwiches were evaluated by flatwise compression and three point bending tests. The samples with higher elastic modulus usually exhibited higher collapse strength for each thickness set of foam and foam based sandwiches. Also, the core thickness increase led to the increase of overall flexural collapse load and GFPP presence promoted the strength of the sandwiches and dissipated energy values. In order to investigate the blast response of the sandwich panels, the quasi-static sandwich panel analysis was related to dynamic blast loadings. For this purpose, the sandwich composites were subjected to compression loading with a specially designed loading fixture and the corresponding test method is called as “simulated blast test”. The sandwiches were assumed as single degree of freedom mass-spring systems to include the dynamic effect. The peak deflections and survivability of the panels under blast loading were predicted based on the formulations reported in the literature. To evaluate the blast response of the monolithic materials, composites and sandwich panels, blast testing was performed using specially designed blast test frame system and 0.5 to 6 kg TNT explosives. Test results revealed that composites such as GFPP exhibited successful results against blast explosions.
Development of adhesively bonded glass fiber reinforced polypropylene/aluminum based fiber metal laminates (FMLs)
(Izmir Institute of Technology, 2019-07) Türkdoğan, Ceren; Tanoğlu, Metin; Tanoğlu, Metin
One of the most important steps during the production of adhesively bonded fiber metal laminates (FMLs) is adhesive bonding. In glass fiber reinforced polypropylene/aluminum laminates, it is very difficult to provide good bond strength. In order to solve this problem, applying various surface pre-treatments to the bonding surfaces prior to adhesively bonded is very important for good performance properties. In the present study, glass fiber reinforced polypropylene (GFPP) composite plates were manufactured from (±450) fabrics using hot press compression method. Tensile, Charpy impact and flexural tests were performed to investigate the mechanical properties of the composites. The produced GFPP plate and Al were used as the adherends and polyurethane-based film as adhesive in FMLs. While manufacturing FMLs, various surface modification techniques (silane and sandblasting pre-treatment) were applied to aluminum for good adhesion of GFPP and Al interface and their effect on the adhesive properties of GFPP/Al laminates were presented. The mechanical properties lap shear, and flexural strength and Mode-I fracture toughness of the adhesively bonded Al/GFPP laminates were investigated to evaluate the effects of surface treatments. Scanning electron microscope (SEM) was used to examine the fracture surfaces. Single lap shear test showed that the adhesion of the GFPP/Al was improved by treatments of aluminum surfaces with silane and sandblasting. According to Mode-I fracture toughness values, silane treated specimens gave the best results. Based on the flexural test results, no significant change was observed in the flexural strength values of treated specimens compared to non-treated specimens.
Development of aluminum honeycomb cored carbon fiber reinforced polymer composite based sandwich structures
(Izmir Institute of Technology, 2016-12) Okur, Mehmet Ziya; Tanoğlu, Metin
Lightweight composite sandwich structures are composed of composite structures that are laminated between thin stiff facesheets bonded to a thicker lightweight core. These structures have high potatial to be used in civil engineering applications, marine, aerospace industry etc. applications due to their high strength to weight ratios and energy absorption capacity. In these structures, the bending loads are generally carried by the force couple formed by the face sheets while the shear loads are carried by the lightweight core materials. Main purpose of the core material is to provide a high moment of inertia. Therefore, under flexural loading, sandwich panels have higher specific mechanical properties relative to the monocoque structures. Also, the core resists transverse forces and stabilizes the laminates against global buckling and local buckling. The resulting structure provides increased buckling resistance and its rigidity. In this study, sandwich composite structures were developed with carbon fiber reinforced polymer composite facesheets and the cores made by Aluminum (Al) based honeycomb with various thicknesses. Carbon fiber/epoxy composite facesheets were fabricated with non-woven unidirectional (UD) fabrics (with 0o/90o orientation) and epoxy resin by vacuum infusion technique. Al honeycomb layers were sandwiched together with carbon/epoxy facesheets using a thermosetting adhesive. Mechanical tests were carried out to determine the mechanical behavior of face sheets, aluminum cores and the composite sandwich structures. Effect of core thickness on the mechanical properties of the sandwich structures was investigated.
Development of antibacterial polymer based nanocomposite materials
(Izmir Institute of Technology, 2015-03) Abatay, Ezgi; Tanoğlu, Metin; Arslanoğlu, Alper; Tanoğlu, Metin
Human beings are often infected by microorganisms such as bacterium, mold, yeast, virus, etc. in the living environment. It became a requirement and a necessity to create sterile fields in areas. Composite stones are one of the main materials that can be used for the contact surfaces in indoor and outdoor places due to their being of highly resistant to abrasives, chemicals and impacts. Research has been intensive in antibacterial material containing various inorganic substances. The aim of this thesis is investigating the antibacterial effect of inorganic substances such as silver, zinc oxide, calcium oxide, titanium oxide and magnesium oxide on stone products. This study also deals with the silver doped zinc oxide powder and their antibacterial efficacies. Stone product is formed of mainly two type compound which are quartz aggregates as reinforced and filler and thermoset polyester resin as matrix. The manufacturing process begins with selection of raw quartz materials. They are crushed and blended in the ratio of 90 % quartz aggregates to 10% polyester matrix and other additives such as antibacterial agent, pigment. These united constituents are used for production of composite stones by applying those combined vacuum, vibration and pressing processes which are named as vibropress, simultaneously. Following it, they are subjected to surface preparation and polishing processes. In this study, mechanical, thermal, and morphological properties of the particles, polyester matrix and stone product were investigated. Antibacterial efficacies of these were investigated based on colony-count method against gram negative (E.coli) and gram positive (Bacillus subtilis) bacteria. Silver-containing stone samples showed best antibacterial property about ninety-nine percent reduction.
Development of carbon black-layered clay/epoxy nanocomposites
(Izmir Institute of Technology, 2008) Pekşen Özer, Bahar Başak; Tanoğlu, Metin; Tanoğlu, Metin
In 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.
Citation Count: 14
Development of electrically conductive and anisotropic gel-coat systems using CNTs
(Elsevier Science Sa, 2013) Yardimci, Atike Ince; Tanoglu, Metin; Selamet, Yusuf; Tanoğlu, Metin
Electrical conductivity of an unsaturated thermoset polyester based gel-coat system containing 0.05 wt.% of carbon nanotubes (CNTs) was investigated. The CNTs used were synthesized by chemical vapor deposition method by methane decomposition and Raman characterization showed that they were mostly single walled and high quality. To disperse CNTs in the gel-coat resin, 3-roll milling technique was used. It was found that as the CNTs are added to gel-coat system, resistivity value decreases significantly while neat gel-coat showed a high resistivity. By the application of an AC electrical field during curing process, it was attempted to align CNTs in the gel-coat resin and an electrically anisotropic polymer was obtained. (C) 2012 Elsevier B.V. All rights reserved.
Development of fiber reinforced cylindrical composite structures by filament winding technique
(Izmir Institute of Technology, 2019-12) Aydın, Mustafa; Tanoğlu, Metin; 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