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    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, Mursel
    In 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.
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    Electrospun TiO2/ZnO/PAN hybrid nanofiber membranes with efficient photocatalytic activity
    (ROYAL SOC CHEMISTRY, 2017) Yar, Adem; Haspulat, Bircan; Ustun, Tugay; Eskizeybek, Volkan; Avci, Ahmet; Kamis, Handan; Achour, Slimane
    Electrospun polyacrylonitrile (PAN) nanofibers were decorated with TiO2, ZnO and TiO2/ZnO nanoparticles for the first time to prepare flexible multifunctional nanofibrous membranes. First, the arc-discharge process was utilized to prepare TiO2, ZnO and TiO2/ZnO nanoparticles and then the hybrid electrospun nanofibers were spun from PAN/nanoparticle colloids. X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were utilized to characterize the resulting nanoparticles and nanofiber loaded nanoparticles. The microscopic investigations revealed that the specifically TiO2 nanoparticles tend to agglomerate within the PAN nanofiber resulting increased surface roughness; however, ZnO nanorods with 1D morphology are aligned as parallel to the fiber axis. Photocatalytic activity of the hybrid nanofibers was performed by pursuing the degradation of malachite green (MG) dye under UV light irradiation. The fabricated TiO2/ZnO/PAN hybrid nanofibers showed excellent photocatalytic efficiency with at least two times higher reaction rates compared to the bare PAN nanofibers. The results suggest that the photocatalytically active TiO2/ZnO/PAN hybrid nanofibers can be considered as filtering materials for a variety of applications in the fields of wastewater systems without the need of post processing stages for separating catalysts from the liquid medium.
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    Enhanced fatigue performances of hybrid nanoreinforced filament wound carbon/epoxy composite pipes
    (ELSEVIER SCI LTD, 2016) Ustun, Tugay; Eskizeybek, Volkan; Avci, Ahmet
    In filament wound composite pipes matrix cracking, as an initial damage mechanism during fatigue loading, can initiate a damage sequence that can result in catastrophic failure of the pipes. Matrix modification using nanostructured fillers is an emerging approach to develop new fatigue-resistant composite materials. The aim of this study to investigate the fatigue performance experimentally, and observe macroscopic and microscopic damage mechanisms of carbon fiber/epoxy filament wound composite pipes toughened by carbon nanotubes ( CNTs) and boron nitride nanoplates (BNNPs). The effectiveness of nanofillers with different morphologies on fatigue damage development and their micro/nano reinforcing mechanisms were discussed. The fatigue tests with positive cycling pressure loading were performed at three different load levels as 50%, 60%, and 70% of the static burst strength of each samples. S-N curves were obtained according to fatigue test and lifetime of the fabricated hybrid composite pipes were evaluated. The addition of nanoscale reinforcements increase fatigue performance of the composite pipes for all cases. To analyze damage initiation and final damage, microscopic analyses of the fracture surfaces were utilized. The fractographic investigations revealed that the morphologies of nanofillers play a key role on improving mechanical performance by generating different nano- and micro-scale toughening mechanisms. (C) 2016 Elsevier Ltd. All rights reserved.
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    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, Ahmet
    In 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.