Yazar "Sahin, Omer Sinan" seçeneğine göre listele
Listeleniyor 1 - 11 / 11
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Boron nitride-MWCNT/epoxy hybrid nanocomposites: Preparation and mechanical properties(Elsevier, 2014) Ulus, Hasan; Ustun, Tugay; Eskizeybek, Volkan; Sahin, Omer Sinan; Avci, Ahmet; Ekrem, MurselIn this study, production and mechanical properties of hybrid nanocomposites have been investigated. Hybrid nanocomposites are consisting of boron nitride nanoplatelets (BN) and multiwall carbon nanotubes (MWCNT) embedded in epoxy resin. The BN and MWCNT were mixed to epoxy resin in different weight fractions and mixtures were utilized for tensile test specimen production. The synthesized BN and produced hybrid nanocomposites were characterized by SEM, TEM, XRD, FT-IR and TGA analyses. The elasticity modulus and tensile strength values were obtained via tensile tests. The fracture morphologies were investigated after tensile test by means of scanning electron microscopy. (C) 2013 Elsevier B.V. All rights reserved.Öğe The Effect of Ultrasonic Cleaning Upon Mechanical Properties of Metal Matrix Composites(Springer India, 2021) Aslan, Abdullah; Salur, Emin; Gunes, Aydin; Sahin, Omer Sinan; Karadag, Hakan Burak; Akdemir, AhmetThe aim of this study is to produce composite materials by recycling metallic chips, which are found in industry as a large amount of waste. In addition, it is aimed to investigate the effect of ultrasonic cleaning process as the consolidation behavior and mechanical properties of bulk material directly depend on the cleaning of waste metallic chips. In the present investigation, spheroidal graphite cast iron (GGG-40) was employed as reinforcement material in tin bronze (CuSn10) matrix system. GGG-40 and CuSn10 chips were cleaned by ultrasonic agitation in water for 20 and 40 min. Consolidation of the cleaned metallic chips was achieved with a hot press by applying 820 MPa pressure under 450 degrees C, and the cylindrical and prismatic metal matrix composite materials with different reinforcement ratios were successfully produced. Energy-dispersive X-ray and scanning electron microscopy analyses were carried out to determine the amount of the oxide removed from the surfaces of chips. The mechanical properties of the samples were determined by hardness, porosity, compression and three-point bending tests. According to the results of the analyses, it was found that CuSn10 surfaces were cleaned from 20%, 50% and GGG-40 surfaces from 35%, 39% oxides during 20- and 40-min cleaning time, respectively. In addition, the results of the mechanical tests revealed that increased ultrasonic cleaning time improves the consolidation quality of metallic chips and it provides successful covering of GGG-40 chips by the CuSn10 chips as a result of a better structural integrity. New machinery parts with high mechanical properties can be produced as a result of recycling of the metallic chips which are available as waste in industry by appropriate cleaning process and this situation makes this study more innovative, economical and environmentally friendly research.Öğe The effects of harsh aging environments on the properties of neat and MWCNT reinforced epoxy resins(Elsevier Sci Ltd, 2021) Aslan, Abdullah; Salur, Emin; Duzcukoglu, Hayrettin; Sahin, Omer Sinan; Ekrem, MurselIn this study, the effects of different harsh aging environments on the chemical and mechanical properties of neat and multiwall carbon nanotubes (MWCNT) reinforced epoxy resins were investigated. The neat and 1 wt% MWCNT reinforced epoxy resins were exposed to four different corrosive environments, namely deionized water, NaCl solution (10 wt% NaCl), H2SO4 solution (10 wt% H2SO4), and HCl solution (10 wt% HCl. The mass variation results revealed that the highest absorption rates were found in specimens aged in both acidic environments. The highest amount of absorption was observed in the H2SO4 environment, measured approximately 3% for neat epoxy, and 6.5% for MWCNT reinforced epoxy resin. FT-IR spectrums showed that the most affected peaks belong to specimens aged in both acidic environments. Tensile test results revealed that the aging process in H2SO4 solution and deionized water deteriorated the strength of specimens. According to the literature, it was reported that the strength of specimens aged in NaCl solution environment is decreased. However, the same trend has not been in this study. In our study, the strength of specimens aged in NaCl solution environment increased impressively by 29%, which makes this study more striking. Another important point analyzed from the tensile test results was that the MWCNT nanoparticle reinforcement adversely affects the strength of the epoxy resin. So, it can be clearly stated that the use of expensive MWCNTs as filler of epoxy resin is not useful to improve its aging resistance. The scanning electron microscope (SEM) and optical microscope images showed that acidic environments result in different fracture mechanisms from typical polymer damaged surfaces reported in available researches. (C) 2020 Elsevier Ltd. All rights reserved.Öğe Enhancement of Wear and Friction Characteristics of Epoxy Resin by Multiwalled Carbon Nanotube and Boron Nitride Nanoparticles(Taylor & Francis Inc, 2015) Duzcukoglu, Hayrettin; Ekinci, Serafettin; Sahin, Omer Sinan; Avci, Ahmet; Ekrem, Mursel; Unaldi, MahmutEpoxy resins are widely used in engineering applications. However, their low thermal stability limits their usage at high sliding velocities and loads. The mechanical properties and thermal stability of a machine element subjected to friction and wear are very important. In this study, friction and tribology behaviors of multiwalled carbon nanotubes (MWCNTs) and boron nitride (BN)-modified epoxy resin have been investigated. Epoxy resin modified by three different nanoparticle configurations, 0.3% MWCNT, 0.5% BN, and 0.5% MWCNT/0.3% BN, was investigated. The tribological characteristics of nanoparticle-modified epoxy resin were compared with properties of neat resin. The friction and tribological behavior of modified epoxy resin were tested using a ball-on-disc test stand at 1.2 and 1.5 ms(-1) sliding velocities under 10 N applied load. The tests were done under dry condition and 1,800 m distance. The friction coefficient, wear loss, and temperature increase during testing were recorded and compared with that obtained for neat epoxy. It is observed that nanoparticle modification resulted in enhanced wear resistance and a reduction in friction coefficient and working temperatures.Öğe Experimental and statistical analysis of low velocity impact response of filament wound composite pipes(Elsevier Sci Ltd, 2018) Gemi, Lokman; Kayrici, Mehmet; Uludag, Muhammet; Gemi, Dilek Soylu; Sahin, Omer SinanNowadays, filament wound composite pipes (GRP) are used as a structural element in many applications such as natural gas and oil transmission lines, and portable bridge constructions for military purposes. GRP pipes can expose to impact loading from various causes. This loading can cause an invisible level of damage. Thus, the detection and evaluation of such damages are of great importance. In this study, the low velocity impact response of (+/- 55 degrees)(3) filament wound E-glass/epoxy composite pipes has been studied. The pipes have been subjected to drop weight impact loading with various impact energies. The force-time and force-displacement relations have been examined. The impact damage formation was also evaluated. It is concluded that the damage development in the pipes is controlled by displacement trough radial direction. The obtained results were evaluated statistically by means of Weibull approach. Microscopy analysis of impacted region revealed that debonding, radial cracks, transfer cracks and delamination damage modes are the main observed damage modes.Öğe Experimental investigation of axial compression behavior after low velocity impact of glass fiber reinforced filament wound pipes with different diameter(Elsevier Sci Ltd, 2022) Gemi, Dilek Soylu; Sahin, Omer Sinan; Gemi, LokmanThe GRP (Glass Reinforced Polymer) composite pipes produced by filament winding (FW) technique are used in many applications such as the transmission of pressurized gases, liquids, oil, and natural gas transmission. These composite pipes may be subjected to low velocity impacts during production and/or service for various reasons. The impact on the composite pipes may lead to invisible damages such as matrix crack, fiber damage, and inter layer separation. In this study, pipes with three different diameters (empty set54, empty set72, and empty set96 mm) were produced to investigate the damage caused by low velocity impact and to determine the effect of these damages on the strength losses of the composite pipe. The pipes were subjected to low velocity impact test according to ASTM D 7136 with 1.5, 2, 2.5, and 3 m/s impact velocities. In order to examine the effects of impact damages on the strength of pipes, Compression after impact (CAI) tests were performed on pre-damaged pipes according to ASTM D 7137 and Force-Displacement and Stress-Strain relations were obtained. The results of impacted samples were compared with the behavior of undamaged samples. After the experiments, macro/micro damage analyses of GRP pipes were performed by optical microscope and SEM imaging.Öğe Experimental investigation of fatigue damage formation of hybrid pipes subjected to impact loading under internal pre-stress(Elsevier Sci Ltd, 2017) Gemi, Lokman; Sahin, Omer Sinan; Akdemir, AhmetIn this study, the effect of impact loading upon fatigue behavior of hybrid composite pipes has been investigated. The composite pipes were subjected to tangential pre-stress as 3-48 MPa according to ANSI/AWWA C950 standard than, subjected to low velocity impact at 20 J. The impact pre-damaged pipes then subjected to cyclic loading at 50% sigma ult in accordance with ASTM D 2992-06. It is also observed that increasing the tangential pre-stress decreases impact damage area and increases fatigue life of the pipe. It is also showed that impact pre-damage are not effective on the fatigue life of the pipe at the pre-stress level of 24 MPa. (C) 2017 Elsevier Ltd. All rights reserved.Öğe Experimental investigation of the effect of diameter upon low velocity impact response of glass fiber reinforced composite pipes(Elsevier Sci Ltd, 2021) Gemi, Dilek Soylu; Sahin, Omer Sinan; Gemi, LokmanThe GRP (Glass Reinforced Polymer) composite pipes produced by filament winding technique are used in many fields such as the transmission of pressurized chemical liquids, industrial liquids, oil and natural gas transmission and construction materials. GRP composite pipes may be subjected to low velocity impacts for various reasons both during installation and service. The impact on the GRP composite pipe wall may lead to some nonvisible damages such as matrix crack, fiber damage, delamination and inter-layer separation. Composite pipes suffered strength loss due to these damages caused by impact cannot support the expected strength values during service. Pipes with three different diameters (054, 072 and 096 mm) were produced to investigate the damage caused by low velocity impact and to determine the effect of these damages on the strength losses of the composite pipe. In order to investigate the influence of low velocity impact damage, the produced pipes were subjected to impacts at the velocity of 1.5, 2, 2.5 and 3 m/s according to ASTM D 7136 and preliminary damage was formed. During low velocity impact tests, Force-Time, Force-Displacement and Energy-Time graphs were obtained and dynamic behavior of the pipes were examined. With the increase in diameter; it has been observed that the effect of low velocity impact is reduced and the damage after impact transformed into delamination damage rather than multiple damage.Öğe Friction and Wear Performance of Epoxy Resin Reinforced With Boron Nitride Nanoplatelets(Asme, 2018) Ekrem, Mursel; Duzcukoglu, Hayrettin; Senyurt, Muhammet Ali; Sahin, Omer Sinan; Avci, AhmetIn this study, the effects of addition of boron nitride nanoplatelets (BNNPs) upon friction and wear behavior of epoxy resin have been investigated by using pin-on-disk test. It has been reported in the literature that certain amounts of BNNP addition can be useful for enhancement of mechanical properties. Therefore, it is very important to obtain the effect of such addition upon friction and wear performance of epoxy resin. BNNPs have been incorporated at 0.3-0.5-0.7-1 wt %. It is shown that BNNP addition results in decrease in friction coefficient and wear. It is also shown that the best results are obtained with 0.5% nanoplatelet addition. It is also observed that heat conduction of epoxy resin is enhanced by the nanoplatelet addition.Öğe Mechanical properties and microstructure of composites produced by recycling metal chips(Springer, 2018) Aslan, Abdullah; Gunes, Aydin; Salur, Emin; Sahin, Omer Sinan; Karadag, Hakan Burak; Akdemir, AhmetIn this study, the processing and mechanical properties of porous metal matrix composites (MMCs) composed of spheroidal cast iron chips (GGG40) and bronze chips (CuSn10) and formed by hot isostatic pressing were investigated. Bronze chips (CuSn10) were used as a matrix component, and spheroidal cast iron (GGG40) chips were used as a reinforcement component. The MMCs were produced with different CuSn10 contents (90wt%, 80wt%, 70wt%, and 60wt%). The hot isostatic pressing process was performed under three different pressures and temperatures. The produced MMCs were characterized using density tests, Brinell hardness tests, and compression tests. In addition, the consolidation mechanism was investigated by X-ray diffraction (XRD) analysis and scanning electron microscopy. The test results were compared with those for bulk CuSn10 and bulk GGG40. Mechanical tests results revealed that the metallic chips can be recycled by using hot pressing and that the mechanical properties of the produced MMCs were similar to those of bulk CuSn10. XRD and microscopy studies showed that no intermetallic compounds formed between the metallic chips. The results showed that the CuSn10 and GGG40 chips were consolidated by mechanical interlocking.Öğe Thermal stability and adhesive strength of boron nitride nano platelets and carbon nano tube modified adhesives(Sage Publications Ltd, 2018) Ekrem, Muersel; Sahin, Omer Sinan; Karabulut, Salim Egemen; Avci, AhmetThe effect of multi-walled carbon nanotube and/or boron nitride nano platelets usage on shear strength and thermal stability of epoxy based adhesives have been investigated. Commercially available diglycidyl ether of bisphenol A based epoxy was used as matrix and reinforced by using nanofillers. The resulting adhesive was tested for its shear-lap adhesion to aluminum alloy sheets (2024-T3). The nano particles modified epoxy adhesives were characterized by Fourier transform infrared, differential scanning calorimetry, and thermal gravity analyses analysis. These characterizations revealed that incorporation of nano particles can result in enhancement in chemical stability. Single lap strength joint testing was conducted in accordance with ASTM-D-1002-10 standard. Fracture morphologies and the effects of multi-walled carbon nanotubes and boron nitride nano platelets on epoxy adhesive were investigated after shear tests by means of scanning electron microscopy. Compared to neat epoxy, increases of 30% in shear strength and 57% in energy required to break joints have been obtained by multi-walled carbon nanotube/boron nitride nano platelet modification.
