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Öğe Ark deşarj yöntemi ile bor nitrür nano levha üretimi karakterizasyonu ve karbon kumaş/epoksi kompozitlerin mekanik özelliklerine katkısının incelenmesi(Selçuk Üniversitesi Fen Bilimleri Enstitüsü, 2014-01-30) Ulus, Hasan; Avcı, AhmetBu tez çalışmasında, malzeme biliminde nanoparçacık takviyeli kompozitlerin geliştirilmesinde yeni ve ilgi çekici bir konu haline gelen bor nitrür nanolevhaların ark deşarj yöntemi ile sıvı azot ortamı içerisinde üretimi gerçekleştirilmiştir. Üretilen yapıların karakterizasyonlarının belirlenmesinde taramalı elektron mikroskobu, geçirimli elektron mikroskobu, X-ışınları difraksiyonu ve Fourier dönüşümlü infrared spektroskopisi analizlerinden yararlanılmıştır. Daha sonrasında ise bor nitrür nanolevha (BNNL) takviyeli ve epoksi matrisli polimer nano kompozitlerin modifikasyonu çalışılmıştır. Üretilen nanokompozitler çekme deneylerine maruz bırakılmış ve bor nitrür nanolevha katkısının mekanik ve termal özelliklere etkisi araştırılmıştır. Son olarak VARTM yöntemi ile BNNL-karbon kumaş/epoksi hibrit tabakalı kompozitler üretilmiş ve bor nitrür takviyesinin çekme ve eğilme davranışlarına etksi incelenmiştir. Deneylerin ardından numunelerin kırılma yüzeyleri taramalı elektron mikroskobu ile görüntülenerek numunelerin hasar mekanizmaları incelenmiştir.Öğe Effects of alumina nanoparticles on dynamic impact responses of carbon fiber reinforced epoxy matrix nanocomposites(ELSEVIER - DIVISION REED ELSEVIER INDIA PVT LTD, 2018) Kaybal, Halil B.; Ulus, Hasan; Demir, Okan; Sahin, Omer S.; Avci, AhmetThe influence of alumina (Al2O3) nanoparticles addition upon low-velocity impact behaviors of carbon fiber (CF) reinforced laminated epoxy nanocomposites have been investigated. For this purpose, different amounts of Al2O3 nanoparticles ranging from 1 to 5 wt% were added to the epoxy resin in order to observe the effect of nanoparticle loadings. CF reinforced epoxy based laminated nanocomposites were produced using Vacuum Assisted Resin Infusion Method (VARIM). The low velocity impact (LVI) tests performed according to the ASTM-D-7136 standard under 2, 2.5 and 3 m/s impact velocities. After LVI testing, the damage formations within composites were examined by using scanning electron microscopy (SEM). The results of this study showed that addition of Al2O3 nanoparticles provided a significant improvement in impact damage resistance. The highest damage resistance and minimum energy absorption were observed for 2 wt% Al2O3 nanoparticles loadings. As a result, we can confidently claim that the addition of the Al2O3 nanoparticles in CF/epoxy composites has considerably affected the dynamic response of the nanocomposites. (C) 2018 Karabuk University. Publishing services by Elsevier B.V.Öğe Enhancement of Flexural and Shear Properties of Carbon Fiber/Epoxy Hybrid Nanocomposites by Boron Nitride Nano Particles and Carbon Nano Tube Modification(KOREAN FIBER SOC, 2015) Ulus, Hasan; Sahin, Omer Sinan; Avci, AhmetIn this study, the effect of boron nitride nano particle (BNNP) and/or carbon nanotube (CNT) adding for epoxy modification upon tensile, flexural and shear properties of epoxy resin and carbon fiber (CF) laminated nanocomposites were investigated. Epoxy based polymer nanocomposites were prepared by conventional casting in stainless steel mold and the CF/epoxy laminated nanocomposites were produced via vacuum assisted resin transfer molding (VARTM). Experimental results showed that the tensile, shear and flexural properties of epoxy nanocomposites and CF/epoxy laminated nanocomposites considerably increased by adding nanoparticle. Scanning electron microscopy (SEM) was utilized in order to determine damage formation of experimented nanocomposite samples. The results of laboratory tests showed that the highest values of mechanical properties were obtained for BNNP-CNT hybrid nanocomposite specimens. Bending stiffness increasement values of BNNP-CNT/Epoxy and BNNP-CNT-Epoxy/CF achieved by 27.5 %, and 38.5 %, respectively. Shear strength increasement for BNNP-CNT/Epoxy and BNNP-CNT-Epoxy/CF were determined by 23 %, and 90 %, respectively.Öğe Evaluating the effectiveness of nanofillers in filament wound carbon/epoxy multiscale composite pipes(ELSEVIER SCI LTD, 2016) Üstün, Tugay; Ulus, Hasan; Karabulut, Salim Egemen; Eskizeybek, Volkan; Şahin, Ömer Sinan; Avcı, Ahmet; Demir, OkanThe performance of filament wound (FW) composite pipes is considered to be fundamentally governed by fiber properties and winding angles; however, matrix dominated properties such as axial and hoop strengths are also responsible in design of FW composite pipes. This paper presents the experimental results of a project aiming to assess the benefits of addition of carbon nanotubes (CNTs) and/or boron nitride nanoplates (BNNPs) as nanofillers within epoxy matrix of FW carbon fiber composite pipes. The nanofillers enhance the burst and hoop strengths up to 17.0% and 31.7%, respectively, over the control samples. Failure analysis revealed that the morphologies of nanofillers play an important role on the matrix toughening and strengthening the fiber matrix interface. Highest mechanical performance of the multiscale composite pipes was obtained with the addition of CNTs and BNNPs within the epoxy matrix concurrently related with the synergetic effect of the two different nanofillers. (C) 2016 Elsevier Ltd. All rights reserved.Öğe Influence of Nano-CaCO3 Particles on Shear Strength of Epoxy Resin Adhesives(2017) Kaybal, Halil Burak; Ulus, Hasan; Avcı, AhmetEpoxy resins are a very common type of adhesive materials in several fields like the automotive industry, marine, probably the most important is in the aerospace industry. Adhesive joints of carbon fiber reinforced epoxy composite laminates are worked using an epoxy resin as the adhesive. In this paper, Adhesive joints were modified nano-CaCO3 in order to enhance the shear strength of epoxy adhesives. The enhancements of shear strength of epoxy adhesive joints reinforced with different nano-CaCO3 particles loading have been studied. The adhesive properties were measured by tensile lap shear test as a function of nano-CaCO3 amount and damaged adhesive surface roughness. Also, the fracture surfaces were examined with Scanning Electron Microscopy (SEM)Öğe Low-velocity impact behavior of carbon fiber/epoxy multiscale hybrid nanocomposites reinforced with multiwalled carbon nanotubes and boron nitride nanoplates(SAGE PUBLICATIONS LTD, 2016) Ulus, Hasan; Ustun, Tugay; Sahin, Omer Sinan; Karabulut, Salim Egemen; Eskizeybek, Volkan; Avci, AhmetIn this article, the mechanical properties and dynamic response of hybrid filler-modified epoxy/carbon fiber multiscale composites were investigated. The hybrid fillers composed of multiwalled carbon nanotubes and boron nitride nanoplates were dispersed in epoxy resin and used as matrix material. The multiscale hybrid laminated composites were stacked symmetrically consisting of 10 plies of woven carbon fibers and fabricated by vacuum infusion technique. The mechanical properties of the hybrid composites were investigated by tensile tests. Impact response and energy absorption capacity were investigated by using weight drop test method and the tests were performed according to ASTM-D-7136 standard with impact energies of 5, 10, and 15J. The impact force and displacement versus interaction time were measured. The impulsive force, energy absorption capability, and damage formation were also investigated. It is observed that when the resin is modified by nanoparticles, both strength and the % strain at fracture increase considerably. However, it is shown in the subject manuscript that the enhancement of mechanical has not fully transferred to dynamic response and energy absorption capacities of nanocomposites.Öğe Static and dynamic mechanical responses of CaCO3 nanoparticle modified epoxy/carbon fiber nanocomposites(ELSEVIER SCI LTD, 2018) Eskizeybek, Volkan; Ulus, Hasan; Kaybal, Halil B.; Sahin, Omer S.; Avci, AhmetMatrix modification of carbon fiber reinforced polymer composites with nanoparticles is an effective way to improve its matrix dominated properties. After nanoparticle modification, understanding mechanical properties is important in structural applications, and improvement of such properties can lead to the usage in the wider fields. This study aimed to investigate experimentally static and dynamic mechanical behaviors of CaCO3 modified epoxy/carbon fiber nanocomposites. For this, we filled various amounts of CaCO3 nanoreinforcements into the epoxy matrix, and the nanoreinforced epoxy was used to impregnate carbon fabrics (CF) by utilizing vacuum assisted resin infusion method (VARIM). The prepared fiber reinforced nanocomposites were subjected to tensile, bending and low velocity impact loadings. As a result of all experiments, the tensile strength of CF/epoxy nanocomposites increased about 48% with the addition of 2 wt% CaCO3 nanoreinforcement. The flexural strength enhancements were also determined as 47% for the same CaCO3 nanoreinforcement loading. Besides, by utilizing low-velocity impact tests, we revealed that the CaCO3 nanoparticle reinforced CF/epoxy nano composites exhibited higher impact performances compared to neat CF/epoxy composites. The resulting fracture morphologies were examined by electron microscopy to disclose related mechanical toughening mechanisms. Based on the morphological analysis, crack pinning, crack deflection and debonding of nanoparticles were the primary reasons leading to the improvement of toughness. The authors concluded that the addition of the CaCO3 nanoreinforcements in CF/epoxy composites has significantly influenced the mechanical and physical properties of the nanocomposites.Öğe Structural performance evaluation on aluminum plates retrofitted with composite: Impact of hybrid (bonded/bolted) joining methods under the flexural loading(Selçuk Üniversitesi, 2022) Ulus, Hasan; Kaybal, Halil BurakEngineering materials lose their mechanical performance due to environmental loadings during service, and they require reinforcement. Recently, externally jointed metallic members have been regarded as an effective technique for strengthening structures thanks to the composites being light and having good mechanical properties. Although the traditional methods (bonded and/or mechanical joining) have been widely used for combining, hybrid joints have recently become popular to take advantage of the load transfer efficiency of both techniques. On the other hand, it is essential to know which component the stress should be applied as a design criterion and how the damage behavior has changed accordingly. Since the member below the neutral axis is subjected to tensile and the upper is subjected to compressive stresses during bending loading, it is essential to understand how structural behavior is affected by the reinforcement in both cases. This work investigated the flexural behavior of bolted/bonded hybrid jointed aluminum-basalt composite, in the case of composite is below the neutral axis and aluminum below the neutral axis. Different damage modes were observed depending on different loading conditions and used joining techniques. Experiments indicate that applying the hybrid joining technique enhanced load-carrying capacity significantly attributed to bolts' restriction of shear deformation. This paper extends the understanding of aluminum retrofitting with composites and provides considerable suggestions for the joining method.
