Yazar "Tatar, Ahmet Caner" seçeneğine göre listele

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    The effect of halloysite nanotube modification on wear behavior of carbon-aramid fiber reinforced hybrid nanocomposites
    (Wiley, 2022) Cetin, Mehmet Emin; Bastosun, Yusuf; Tatar, Ahmet Caner; Cetin, M. Huseyin; Demir, Okan; Onal, Gurol; Avci, Ahmet
    In this study, the carbon-aramid fiber reinforced hybrid composites are fabricated using a vacuum-assisted hand lay-up method using halloysite nanotubes (HNTs) modified epoxy matrix. Ball-on-disk wear tests are performed to analyze the tribological effect of neat and HNTs-added specimens at 10, 15, and 20 N loads and 1 m/s sliding speed. Additionally, the wear rate and friction coefficient results are obtained to investigate the effect of the HNTs on the tribological behavior of hybrid composites. The wear mechanism of neat and nanocomposite specimens is specified by scanning electron microscopy (SEM) images, and the elemental analysis of worn surfaces is performed using EDX. Finally, the surface morphology is evaluated with 3D topography images. Additionally, thermal camera images are used to identify the thermal conductivity effect of HNTs on wear. The wear test results show that HNTs-addition to composite decreased the friction coefficient by 9%, 10%, and 11% for 10 N, 15 N, and 20 N loadings, respectively. The wear rate is also decreased average by 75% for wear loadings. Surface form images acquired from 3D topography support the enhancement in the friction coefficient and wear rate values. Furthermore, thermal camera images show that thermal conductivity improvement on the contact region is attributed to well thermal properties of HNTs. Furthermore, the solid-lubricant characteristic of HNTs as forming tribofilm is determined as the main reason for the enhanced tribological performance of nanocomposites. Finally, a detailed wear mechanism is proposed to explain the wear behavior of HNTs-added carbon-aramid hybrid composites based on SEM images.
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    Effects of cryogenic and warm temperatures on quasi-static penetration resistance of carbon-aramid hybrid nanocomposites reinforced using halloysite nanotubes
    (Elsevier, 2021) Cetin, Mehmet Emin; Tatar, Ahmet Caner; Demir, Okan; Onal, Gurol; Avci, Ahmet
    The quasi-static penetration test of a composite structure aims to measure impact behavior under the out-of plane loadings without dynamic and rate effects. In this study, carbon-aramid reinforced nanocomposites were manufactured by vacuum-assisted resin transfer molding and hand lay-up techniques and characterized by quasi-static penetration tests. Halloysite nanotubes (HNTs) were added to epoxy resin as nanofillers. Quasi-static punch shear test (QS-PST) was performed using a 12.7-mm cylindrical punch with a 50.8-mm support span. QSPSTs tests were carried out at-50 degrees C,-25 degrees C, 0 degrees C, 25 degrees C, and 50 degrees C to determine the effect of temperature on quasi-static penetration behavior of neat and HNT-reinforced carbon-aramid nanocomposites. Absorbed energy values and penetration force-displacement curves were acquired from QS-PSTs for each sample. Photographs of the front and rear sides of the samples were taken and analyzed. Moreover, the samples were cut from the middle, and the damage throughout the thickness of the composite samples were examined. It was observed that for all test samples, damages increased when the temperatures decreased. For the same temperature, nano particle addition to the samples resulted in higher penetration force and less damage. We confirmed the possibility of increasing penetration resistance and energy absorption capacity by adding HNT to carbon-aramid fibers at cryogenic and warm temperatures.
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    Effects of extreme low temperatures on the impact behavior of boron nitride nanofillers added carbon fiber/epoxy composite tubes
    (Sage Publications Ltd, 2022) Kara, Memduh; Tatar, Ahmet Caner; Kirici, Muhammed; Kepir, Yusuf; Gunoz, Alper; Avci, Ahmet
    This study aims to investigate the low-velocity impact response of boron nitride nanoparticles (BNNPs) added carbon fiber reinforced pipes (CFRPs) at various temperature values. Carbon fiber/epoxy composite specimens with (+/- 55 degrees)(3) winding angles were manufactured with the filament winding method. Low-velocity impact tests were performed with a 15 J energy level at five different temperatures between -196 degrees C and 23 degrees C ranges to understand the cryogenic environment effect on BNNP added carbon fiber reinforced tubes and neat carbon fiber reinforced tubes. The force-displacement and contact force-time graphs were attained in consequence of low-velocity impact tests. The damage areas, their size and characteristics were scrutinized both visually and with the aid of a Microscope. The test results showed that when ambiance temperatures decreased, the damage areas considerably increased both filled with BNNP and without BNNP filament wound carbon fiber reinforced tubes.
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    An experimental evaluation on the dynamic response of water aged composite/aluminium adhesive joints: Influence of electrospun nanofibers interleaving
    (Elsevier Sci Ltd, 2022) Ulus, Hasan; Kaybal, Halil Burak; Berber, Nihat Erdem; Tatar, Ahmet Caner; Ekrem, Mursel; Ataberk, Necati; Avci, Ahmet
    The impact response of adhesives is a critical design parameter considering their lifetime. Additionally, environmental effects such as water or moisture may cause to degrade of the polymer-based adhesive and shorten its service life. This study aimed to investigate the impact response of water-aged aluminium-composite adhesively bonded single lap joints (SLJs). Nylon 6.6 nanofibers modified with graphene nanoplatelets (GNPs) were introduced in the adhesion areas to increase adhesive performance. The water aging resulted in decreased impact resistance in all cases. However, nanofiber-modified SLJs exhibited comparatively higher impact performance under both non-aged and water-aged conditions. Further, the GNP reinforced nylon 6.6 nanofibers increased the maximum impact load by 15 and 19% compared to neat nanofibers before and after aging, respectively. The fracture surfaces were examined via scanning electron microscopy (SEM) to understand damage and toughness mechanisms. A schematic model has been developed to explain the mechanisms leading to improved bonding performance by applying N6.6 nanofiber reinforcement to the adhesion zone.
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    Impact response of nanoparticle reinforced 3D woven spacer/epoxy composites at cryogenic temperatures
    (Sage Publications Ltd, 2021) Yildirim, Ferhat; Tatar, Ahmet Caner; Eskizeybek, Volkan; Avci, Ahmet; Aydin, Mustafa
    Fiber-reinforced polymer composites serving in harsh conditions must maintain their performance during their entire service. The cryogenic impact is one of the most unpredictable loading types, leading to catastrophic failures of composite structures. This study aims to examine the low-velocity impact (LVI) performance of 3D woven spacer glass-epoxy composite experimentally under cryogenic temperatures. LVI tests were conducted under various temperatures ranging from room temperature (RT) to -196 degrees C. Experimental results reveal that the 3D composites gradually absorbed higher impact energies with decreasing temperature. Besides, the effect of multi-walled carbon nanotube and SiO2 nanofiller reinforcements of the matrix on the impact performance and the damage characteristics were further assessed. Nanofiller modification enhanced the impact resistance up to 30%, especially at RT. However, the nanofiller efficiency declined with decreasing temperature. The apparent damages were visually examined by scanning electron microscopy to address the damage formation. Significant outcomes have been achieved with the nanofiller modification regarding the new usage areas of 3D woven composites.
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    Selectively Reinforced Functionally Graded Composite-like Glass/Carbon Polymer Nanocomposites: Designed for Efficient Bending and Impact Performance
    (Korean Fiber Soc, 2022) Demir, Okan; Tatar, Ahmet Caner; Eskizeybek, Volkan; Avci, Ahmet
    Offshore wind turbine blades (OWTBs) are exposed to various types of loadings during their service life. Moreover, due to their tremendous size, huge investment costs are established, including advanced engineering materials and production process solutions. To decrease their investment cost without sacrificing their mechanical performances, advanced engineering solutions in the view of material selection and design should be implemented. With this motivation, we aimed to develop a novel laminated composite design considering reducing investment costs without compromising the bending and impact resistance of an OWTB. For this, an efficient and cost-effective design of a functionally graded composite (FGM)-like glass/carbon fibers reinforced hybrid polymer composite with a specific stacking sequence was presented. To evaluate mechanical performance of the composite structure, tensile, flexural, and to simulate environmental conditions, low-velocity impact tests were conducted. Furthermore, multi-walled carbon nanotubes (MWCNTs) were also introduced into the polymer matrix to evaluate their effectiveness in the hybridized composite. Drastic improvements in the bending strength (55.8 %) and strain (39.7 %) were obtained compared to the neat carbon fiber reinforced epoxy composites (CFs), especially with the aid of MWCNTs. According to impact tests, it was pointed out that it is possible to obtain higher impact peak forces (around 15 %) compared to neat CFs. However, MWCNTs contributed with slight increments in impact resistance but effectively restricted the impact damage propagation. This study reveals it is possible to tune the bending performance, the absorbed energy, and the damage extension by utilizing glass and carbon fiber laminates in an FGM-like structure.