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Öğe Boron nitride-MWCNT/epoxy hybrid nanocomposites: Preparation and mechanical properties(ELSEVIER SCIENCE BV, 2014) Ulus, Hasam; 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 Effects of polyvinyl alcohol nanofiber mats on the adhesion strength and fracture toughness of epoxy adhesive joints(ELSEVIER SCI LTD, 2018) Ekrem, Mursel; Avci, AhmetThe brittle nature of the polymer based adhesive joints is the major drawback limiting the service life. In this study, electrospun polyvinyl alcohol (PVA) nanofiber mat were introduced within the epoxy adhesive joint region to improve mechanical performance of the joints. The epoxy resin wetted electrospun PVA nanofiber mat were placed in between aluminum adherends and cured uncer vacuum conditions to remove air bubbles and volatiles. The mechanical performance of the reinforced aluminum joints was investigated by utilizing single lap joint (SIJ) and double cantilever beam (DCB). To reveal nano- and micro-scale toughening mechanics of the nanofiber reinforcements, the fracture surfaces were analysed using scanning electronmicroscope (SEM). Mod I fracture toughness and lap shear strength of the adhesively bonded joints were found to increase with addition of PVA nanofiber mats into epoxy adhesive.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 Fatigue behavior of composite to aluminum single lap joints reinforced with graphene doped nylon 66 nanofibers(ELSEVIER SCI LTD, 2018) Polat, Safa; Avci, Ahmet; Ekrem, MurselIt is an important approach to prevent the damage mechanisms that cause sudden fractures during fatigue loading in bonding joints by modifying the matrix with nanostructured materials. The aim of this study is to examine the effect of graphene nanoplates (GNPs) doped nylon 66 (N66) nanofiber mats reinforcement on the fatigue life of composite to aluminum single lap joint. For this purpose, 1 wt%, 3 wt% and 5 wt% GNPs doped N66 nanofibers were produced by electrospinning method. The morphological characteristics, chemical bond structures and % crystallinity of these nanofiber mats was investigated by SEM, TEM, FTIR, DSC analysis. The fatigue tests of the bonding joints with single axis periodic cycle loading were performed at five different load levels as 20%, 30%, 40%, 50% and 60% of the maximum shear strength of each samples. Fatigue life of bonding joints was assessed by S-N curves plotted according to the fatigue results. Damage mechanisms of fractured surface in the bonding joints were investigated with the macro and micro images. The results show that, these composite nanofiber mats have increased the fatigue life of bonding joints in all case.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 Improving electrical and mechanical properties of a conductive nano adhesive(TAYLOR & FRANCIS LTD, 2017) Ekrem, Mursel; Ataberk, Necati; Avci, Ahmet; Akdemir, AhmetIn this experimental study, lap shear strength and electrical conductivity of nanohybrid adhesives containing multi-walled carbon nanotubes (MWCNT) and silver (Ag) nanoparticles were investigated. Ag nanoparticles were produced via arc-discharge method in liquid nitrogen. For characterizing the Ag nanoparticles, X-ray diffraction analysis, transmission electron microscopy, and scanning electron microscopy (SEM) were performed. Tensile lap shear properties were determined in accordance with ASTM D 1002-10 standard. Mechanical and the electrical properties of nanohybrid adhesives were compared with neat epoxy adhesive. The best electrical conductivity of nanohybrid adhesive was obtained for the 1% wt MWCNT-2% wt Ag-contained sample. However, the samples which contain 0.5% wt. MWCNT-0.5% wt. Ag nanoparticles reached the highest lap shear strength. The results showed that Ag nanoparticles enhance the conductivity in the presence of MWCNT. It is concluded that the MWCNT act as conductivity bridges among epoxy adhesive and facilitate the electron transfer. As seen in the tensile test results, the ductility of the adhesive was improved by adding the nanoparticles in to the epoxy resin.