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ÇAKIR, MUSTAFA

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ÇAKIR

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MUSTAFA

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Now showing 1 - 4 of 4
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    PublicationOpen Access
    Multi-featured epoxy composites filled with surface-modified PTFE powders treated by Na-naphthalenide system
    (2023-01-01) AKIN, EMRE; ÇAKIR, MUSTAFA; DEMİRER, HALİL; AKIN E., ÇAKIR M., DEMİRER H.
    This study aimed to produce new multi-featured epoxy composites that are advanced in terms of mechanical properties, wear and impact resistance, and glass transition and heat deflection temperatures. Epoxy composites filled with chemically surface-treated poly (tetrafluoroethylene) (PTFE) powders at various ratios were prepared to obtain these improved properties. The chemical treatment was carried out via a Na-naphthalenide system. After this treatment, the x-ray photoelectron spectroscopy results presented the existence of functional groups such as OH, carbonyl groups, and C=C unsaturation points on the surface of the PTFE powders. On the PTFE surfaces, while the atomic ratios of carbon and oxygen were substantially increased, the fluorine ratio presented a significant decrease after the chemical treatment. However, the wear rates of the novel composites were highly advanced despite this large decrease in the fluorine ratio on the surface of the PTFE powders. Moreover, functional groups such as OH, carbonyl groups, and C=C unsaturation points and spongelike or network structures on the PTFE surfaces provided the opportunity to obtain strong adhesion and interfacial bonding between the surface-modified PTFE powders and the matrix. Strength and modulus values showed substantial enhancement besides the IZOD impact resistance. All glass transition and heat deflection temperatures were also substantially improved.
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    PublicationOpen Access
    A Q-Learning based approach for voltage control in unbalanced distribution system
    (2023-01-01) ÇAKIR, MUSTAFA; CEYLAN, OĞUZHAN; ÇAKIR M., Atak A., Özeren H., CEYLAN O.
    In recent years, with the increasing use of renewable energy sources, voltage regulation in power distribution systems has become a greater challenge due to these sources\" intermittent and variable nature. To address this problem, this paper proposes a Q-learning-based method for voltage regulation in power distribution systems that incorporates tap changer voltage regulators when renewable energy sources are present. The voltage deviation problem is formulated as an optimization problem, and Q-learning is used to find near-optimal solutions that can effectively control voltage deviations and improve the overall performance of the power distribution system. The proposed method is applied to power distribution system using OpenDSS incorporated into Python. The simulations are performed on base case IEEE-123 Bus distribution network and with modifications by adding Photovoltaics. From the simulation results we observed that the proposed algorithm is able to solve the overvoltage and undervoltage problems.
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    PublicationOpen Access
    Mechanical and thermal properties of fumed silica-incorporated silane-terminated urethane/epoxy-interpenetrating polymer network nanocomposites
    (2024-01-01) AKIN, EMRE; ÇAKIR, MUSTAFA; KARTAL, İLYAS; AKIN E., ÇAKIR M., KARTAL İ.
    In this study, it was aimed to improve the mechanical and thermal properties of epoxy materials based on diglycidyl ether of bisphenol-A-based. For this purpose, three different nanocomposite materials were prepared at various ratios including a fumed silica nanoparticle-reinforced epoxy nanocomposite (FSN), an epoxy/silane-terminated urethane (STU) hybrid interpenetrating polymer network (IPN) nanocomposite (SHIN), and a fumed silica-reinforced epoxy/STU hybrid IPN nanocomposite (FSHIN). While synthesizing SHIN, 3-isocyanato propyl trimethoxy silane (ICPTMS) and poly (hexamethylene carbonate) diol were used. The synthesized STU polymer chains were crosslinked by reacting them with TEOS via the sol–gel process. Therefore, hybrid networks were obtained. Moreover, fumed silica nanoparticles were incorporated into the hybrid networks via the sol–gel process for FSHINs. The three different nanocomposite materials exhibited much more improved properties than the neat epoxy. The most prominent nanocomposite was FSHIN. In comparison with the neat epoxy, Young\"s modulus, ultimate tensile strength, and Izod impact resistance values increased at ratios of 53%, 50%, and 223%, respectively. Glass transition temperature values and char yield values increased substantially in all nanocomposites. However, thermal decomposition temperatures increased only for FSNs. Moreover, these values for FSHINs that were very close to those of the neat epoxy were considerably higher than those of SHINs. Highlights: Fumed silica-incorporated silane-terminated urethane/epoxy IPN nanocomposites. Substantially improved mechanical properties and impact resistance. Improved thermal stability.
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    PublicationOpen Access
    Mechanical properties of carbon-aramid hybrid fiber-reinforced epoxy/poly(vinyl butyral) composites
    (2023-01-01) ÇAKIR, MUSTAFA; AKIN, EMRE; ÇAKIR M., AKIN E., Renda G.
    Currently, it is important to manufacture fiber-reinforced epoxy matrix composites with high impact resistance besides their high strength and modulus values for industries such as automotive, aerospace, and aviation due to the brittle structure of epoxy. In this regard, we found the attractive results of the 0.5 wt% poly(vinyl butyral) (PVB)-containing epoxy blend in terms of strength, Young\"s modulus, and impact resistance. These results substantially motivated us to manufacture fiber-reinforced advanced epoxy/PVB matrix composites with 30–60 vol% carbon-aramid fiber ratios. Flexural (three-point bending) and tensile tests were performed to obtain strength and modulus values by measuring the force required to break the fiber-reinforced composite specimens and elongation at break points. Interlaminar shear strength tests were performed by the short beam bending method by measuring the resistance of the composite to delamination. The Charpy impact test was used to measure the energy absorbed during crack formation and fracture propagation. The composites with PVB were generally superior to those without PVB (EPCs). Two types of findings were observed. First, PVB increased the tensile and flexural strength values substantially for the 30 and 40 vol% ratios, but the modulus values slightly decreased. Second, PVB also substantially increased the modulus values for the 50 vol% ratio besides the strength values. It was thought that this result could be attributed to the increase in the compatibility of the fiber/matrix for the 50 vol% ratio. These decreases for EPCs could be derived from the micro-cracks and weaker interface between fiber and matrix.