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Subject: Temperature effect

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Now showing 1 - 3 of 3
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    Conference Object
    Citation - WoS: 5
    Citation - Scopus: 5
    The Effect of the Impactor Diameter and Temperature on Low Velocity Impact Behavior of Cfrp Laminates
    (Amer inst Physics, 2017) Evci, C.; Uyandiran, I.
    Impact damage is one of the major concerns that should be taken into account with the new aircraft and spacecraft structures which employ ever-growing use of composite materials. Considering the thermal loads encountered at different altitudes, both low and high temperatures can affect the properties and impact behavior of composite materials. This study aims to investigate the effect of temperature and impactor diameter on the impact behavior and damage development in balanced and symmetrical CERT' laminates which were manufactured by employing vacuum bagging process with autoclave cure. Instrumented drop-weight impact testing system is used to perform the low velocity impact tests in a range of temperatures ranged from 60 down to -50 degrees C. Impact tests for each temperature level were conducted using three different hemispherical impactor diameters varying from 10 to 20 mm Energy profile method is employed to determine the impact threshold energies for damage evolution. The level of impact damage is determined from the dent depth on the impacted face and delamination damage detected using ultrasonic C-Scan technique. Test results reveal that the threshold of penetration energy, main failure force and delamination area increase with impactor diameter at all temperature levels. No clear influence of temperature on the critical force thresholds could be derived. However, penetration threshold energy decreased as the temperature was lowered. Drop in the penetration threshold was more obvious with quite low temperatures. Delamination damage area increased while the temperature decreased from +60 degrees C to-50 degrees C.
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    Conference Object
    Citation - WoS: 44
    Citation - Scopus: 56
    Three-Dimensional Modeling of a High Temperature Polymer Electrolyte Membrane Fuel Cell at Different Operation Temperatures
    (Pergamon-elsevier Science Ltd, 2016) Caglayan, Dilara Gulcin; Sezgin, Berna; Devrim, Yilser; Eroglu, Inci
    A three-dimensional model for a high temperature polymer electrolyte membrane (PEM) fuel cell having an active area of 25 cm(2) is developed. Triple mixed serpentine flow channel single cell with phosphoric acid doped polybenzimidazole (FBI) membrane is used in the model. Steady-state, isothermal, single phase assumptions are defined for the system. The model is simulated at different temperatures ranging from 100 to 180 degrees C to investigate the influence of operation temperature on the performance of the cell. It is seen that there is an improvement in the performance of the cell as the operation temperature increases. Experimental data are used to validate the model both for single channel and triple mixed serpentine flow channel. Current density distribution is obtained at different operating voltages. The predicted results show that at high operating voltages the local current density is almost uniform; whereas, decreasing operating voltage causes non-uniformities in the local current density. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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    Conference Object
    Citation - WoS: 4
    Citation - Scopus: 3
    Temperature-dependent material characterization of CuZnSe2 thin films
    (Elsevier Science Sa, 2020) Gullu, H. H.; Surucu, O.; Terlemezoglu, M.; Isik, M.; Ercelebi, C.; Gasanly, N. M.; Parlak, M.
    In the present work, CuZnSe2 (CZSe) thin films were co-deposited by magnetron sputtering of ZnSe and Cu targets. The structural analyses resulted in the stoichiometric elemental composition and polycrystalline nature without secondary phase contribution in the film structure. Optical and electrical properties of CZSe thin films were investigated using temperature-dependent optical transmission and electrical conductivity measurements. The band gap energy values were obtained using transmittance spectra under the light of expression relating absorption coefficient to incident photon energy. Band gap energy values were found in decreasing behavior from 2.31 to 2.27 eV with increase in temperature from 10 to 300 K. Temperature-band gap dependency was evaluated by Varshni and O'Donnell models to detail the optical parameters of the thin films. The experimental dark and photoconductivity values were investigated by thermionic emission model over the grain boundary potential. Room temperature conductivity values were obtained in between 0.91 and 4.65 ( x 10(-4) Omega(-1)cm(-1)) under various illumination intensities. Three different linear conductivity regions were observed in the temperature dependent profile. These linear regions were analyzed to extract the activation energy values.