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Öğe A flexible carbon nanofiber and conjugated polymer-based electrode for glucose sensing(Elsevier, 2023) Bulut, Umut; Sayin, Vuslat Oyku; Altin, Yasin; Cevher, Sevki Can; Cirpan, Ali; Bedeloglu, Ayse Celik; Soylemez, SaniyeHerein, a specific and stable biosensor for glucose using a flexible, modified electrode with a carbon nanofiber (CNF) and a novel conjugated polymer including three moieties of benzotriazole, benzodithiophene, and benzenediamine (P-BDT-BTz:BDA) as a platform was designed. For this purpose, polyacrylonitrile (PAN) nanofiber mats were obtained by a solution-based electrospinning method. PAN nanofiber mats were stabilized and carbonized to turn into carbon nanofibers and the sensing platform was formed by combining the nanofibers on a defined area of a flexible polyethylene terephthalate (PET) substrate. In addition, a random conjugated polymer, P-BDT-BTz:BDA, was synthesized, characterized, and used as a modifier of a CNF-coated transducer surface for glucose detection. The effect of each parameter on biosensor response was evaluated. Under optimized conditions, the electrode responded to glucose in a linear concentration range of 20 mu M to 500 mu M with a detection limit of 8.5 mu M. In addition, it was observed that the designed biosensor has a good sensing ability for glucose in beverages. The results of our study show that the proposed amperometric glucose oxidase (GOx)-based biosensor has high specificity, a low limit of detection, and an extended range of linear detection for glucose.Öğe Characterization of organic solar cells using semiconducting polymers with different bandgaps(Walter De Gruyter Gmbh, 2019) Borazan, Ismail; Altin, Yasin; Demir, Ali; Bedeloğlu, AyşePolymer-based organic solar cells are of great interest as they can be produced with low-cost techniques and also have many interesting features such as flexibility, graded transparency, easy integration, and lightness. However, conventional wide bandgap polymers used for the light-absorbing layer significantly affect the power conversion efficiency of organic solar cells because they collect sunlight in a given spectrum range and due to their limited stability. Therefore, in this study, polymers with different bandgaps were used, which could allow for the production of more stable and efficient organic solar cells: P3HT as the wide bandgap polymer, and PTB7 and PCDTBT as low bandgap polymers. These polymers with different bandgaps were combined with PCBM to obtain increased efficiency and optimum photoactive layer in the organic solar cell. The obtained devices were characterized by measuring optical, photoelectrical, and morphological properties. Solar cells using the PTB7 and PCDTBT polymers had more rough surfaces than the reference cell using P3HT. The use of low-bandgap polymers improved I-sc significantly, and when combined with P3HT, a higher V-oc was obtained.Öğe Conducting polymer blends, interpenetrating polymeric networks, and gels based on polyvinyl chloride(Elsevier, 2024) Duygun, İnal Kaan; Altin, Yasin; Çelik Bedeloğlu, AyşeConducting polymers (CPs) are polymers that attract great attention due to their very good electrical and optical properties. However, their mechanical strength and processability are far from the necessary conditions for many applications. On the other hand, polyvinyl chloride (PVC), which is the third most produced polymer in terms of quantity, is a common polymer type whose properties can be changed with many additives and thus can be used in many different fields. The resulting blended films find application in areas such as sensors, supercapacitors, electromagnetic shielding, and antistatic coating. In this section, first of all, the electrical, optical, and mechanical properties of CP/PVC mixtures will be examined. Then, the applications of CP/PVC mixtures will be mentioned. © 2024 Elsevier Inc. All rights reserved.Öğe Effect of graphene oxide-coated jute fiber on mechanical and durability properties of concrete mixtures(Elsevier Sci Ltd, 2024) Ozen, Suleyman; Benlioglu, Arif; Mardani, Ali; Altin, Yasin; Bedeloglu, AyseVarious methods are applied in order to improve the mechanical properties of concrete and to provide ductility. The most common method is the addition of fiber to cementitious systems. The fibers used in cementitious systems are divided into two categories: artificial and natural. Natural fibers are preferred due to their lower production cost, lower environmental impacts such as lower carbon emissions and fossil fuel consumption, biodegradability, lower density and ease of manufacturing. On the other hand, graphene-derived materials have been proven to improve the mechanical and interface properties between fiber and matrix. In this study, the effect of surface treatment of jute fibers with various chemical treatments and graphene oxide coating on the mechanical and some durability performances of concrete mixtures was investigated. For this purpose, the surface of jute fibers was roughened with graphene oxide coating. Within the scope of the experimental study, different fiber concrete mixtures were prepared by adding jute fibers of 30 and 50 mm length to the mixture at 0.25 and 0.5 % of the total volume in addition to the fiber-free control mixture. The fiber was used in 2 different ways, both without any treatment and by coating the surface with graphene oxide. Slump tests were performed on the concrete mixtures produced. The 28-day hardened concrete specimens were tested for compressive strength, flexural strength, modulus of elasticity, ultrasonic pulse velocity and depth of water penetration under pressure. The resistance of the concrete specimens at 300 and 600 degrees C high temperatures and after 300 cycles of freeze-thaw was determined by examining their compressive strength. In addition, the microstructural properties of the jute fiber specimens were examined using Scanning Electron Microscopy (SEM).Öğe Effect of microwave-reduced graphene oxide on the mechanical, thermal, and physical properties of banana fiber reinforced epoxy composites(2025) Altin, YasinThis study presents a comprehensive investigation into enhancing the mechanical and thermal performance of banana fiber-reinforced epoxy composites through the incorporation of microwave-reduced graphene oxide (rGO) as a nanofiller. Graphene oxide (GO) was synthesized from graphite powder via the improved Hummers’ method. Its successful synthesis and subsequent reduction to rGO were confirmed by Fourier-transform infrared (FT-IR) and Raman spectroscopy. Raman analysis revealed a characteristic increase in the defect ratio (ID/IG) from 0.12 for pristine graphite to 0.896 for GO, and further to 0.963 for rGO. This trend indicates the formation of numerous, smaller sp² domains upon reduction, a key factor for effective reinforcement. Composite laminates were fabricated by hand lay-up with rGO loadings of 0, 0.1, 0.2, and 0.5 wt.%. Mechanical and thermal properties were analyzed. The results demonstrated that the effect of rGO is highly dependent on concentration. For tensile properties, the optimal performance was achieved at 0.2 wt.% rGO, while flexural properties were maximized at 0.5 wt.%. Physical property analysis revealed a decrease in composite density with increasing reinforcement content, a trend attributed to the inherent porosity (lumen) of the banana fibers themselves. Optical microscopy images confirmed the homogeneous distribution of fibers in the matrix, a key factor for composite performance. This research highlights the complex role of rGO in natural fiber composites and underscores the importance of optimizing filler content for specific application requirements.Öğe Flexible carbon nanofiber yarn electrodes for self-standing fiber supercapacitors(Sage Publications Inc, 2022) Altin, Yasin; Bedeloglu, Ayse CelikIn this study, polyacrylonitrile (PAN) nanofiber yarns were obtained by twisting the nanofiber mat strips produced in the electrospinning device. On the drum collector, the nanofibers are produced in such a way that the diameter change can be controlled. Through stabilization and carbonization processes, PAN nanofiber yarns were converted to carbon nanofiber (CNF) yarns. The stabilization process stabilized the yarn structure, which was previously unstable, due to thermal treatments. The obtained CNF yarn had a diameter of approximately 360 mu m and an average nanofiber diameter of 123 +/- 20 nm. On a three-electrode system, the electrochemical performance of CNF yarn in 1 m H2SO4 electrolyte was determined using cyclic voltammetry and galvanostatic charge/discharge test methods. The specific capacitance of the CNF yarn electrode was determined to be 145 F/g at a current density of 0.2 A/g. Up to 500 charge/discharge cycles, the specific capacitance increased by approximately 20% and remained constant thereafter. Due to their superior properties such as high surface area, lightweight, and flexibility, CNF yarn electrodes can be used in a wide variety of electronic applications, including energy harvesting, energy storage (supercapacitors, batteries, etc.), and sensors.Öğe Flexible Electrospun PVDF Piezoelectric Nanogenerators with Electrospray-Deposited Graphene Electrodes(Springer, 2023) Unsal, Omer Faruk; Altin, Yasin; Bedeloglu, Ayse CelikToday, there is a great demand for the development of portable, lightweight, flexible, and stable devices that produce and store energy to provide the power that wearable electronics and smart textile materials need. For this purpose, in recent years, researchers have focused on the development of nanofiber-based nanogenerators that have high surface areas thanks to their nanofibrous structures. Therefore, this study presents the development of piezoelectric nanogenerators made of poly(vinylidene fluoride) (PVDF) nanofibers and graphene-based flexible electrodes via electrospray deposition (ESD) technique using electrospinning devices. First, graphene oxide (GO) was electrosprayed onto the PVDF-nanofiber surface, then, the coated GO layer was reduced by chemical treatment to obtain reduced-GO (rGO) and to increase the electrical conductivity. With the ESD technique, it has been observed that graphene oxide nanosheets successfully wrapped on the nanofibers without agglomerating, and this effect was further enhanced by the reduction process. The effect of different thicknesses of graphene electrodes on the efficiency of nanogenerators was investigated. As a result, a maximum peak-to-peak voltage of 1.00 V was produced by a rGO-sprayed nanofiber-based nanogenerator, while 0.688 V was obtained with pure PVDF nanofibers. Also, voltage-per-gram analysis showed that the output voltage was directly related to the electrode morphology and thickness.Öğe Graphene and graphene oxide-coated polyamide monofilament yarns for fiber-shaped flexible electrodes(Taylor & Francis Ltd, 2019) Tas, Mahmut; Altin, Yasin; Bedeloğlu, AyşeIn this study, polyamide monofilament yarn of 3000 tex was coated with graphene oxide (GO) nanomaterial using dip-coating method. The graphene oxide layer was then reduced with green chemical reduction method, resulting in a reduced graphene oxide-coated monofilament yarn. The properties of the graphene oxide and reduced graphene oxide-coated polyamide monofilament yarns were characterized by performing physical, electrical, optical, and morphological investigations. The lowest sheet resistance was measured from seven-layer graphene-coated polyamide monofilament yarn as 3.09 k omega/sq. Moreover, it was measured that 90 degrees and 180 degrees bent seven-layer graphene-coated polyamide monofilament yarns had 3.57 and 3.81 k omega/sq sheet resistance, respectively. Additionally, while PA monofilament yarn has 73.5% transmittance at 550 nm; seven-layer GO and seven-layer graphene have 18.8 and 4.5%, respectively, as expected. On the other hand, the contact angle increased with the reduction of graphene oxide layer on monofilament yarn. The fabricated graphene-coated polyamide monofilament yarns can be used in electrotextiles, solar cells, sensors, and OLEDs as fiber-shaped flexible electrodes.Öğe Graphene oxide and zinc oxide decorated chitosan nanocomposite biofilms for packaging applications(Walter De Gruyter Gmbh, 2020) Terzioğlu, Pınar; Altin, Yasin; Kalemtaş, Ayşe; Bedeloğlu, AyşeRecently, due to sustainable development and environmental protection policies, there is increasing interest in the development of new biodegradable polymer-based multifunctional composites. Chitosan is one of the most remarkable and preferred biopolymers, which is environmentally friendly as well as renewable, biocompatible, and inexpensive. Though it has a wide range of potential applications, the major limitation of chitosan - the problem of poor mechanical performance needs to be solved. In this work, graphene oxide was first produced and then used to manufacture a chitosan/graphene oxide/zinc oxide composite film through a casting method. The properties of the chitosan film and the chitosan/graphene oxide/zinc oxide composite film were investigated using Fourier transform infrared spectroscopy, mechanical, thermal gravimetric, and ultraviolet (UV)-visible spectroscopy analyses. The results showed that the incorporation of graphene oxide and zinc oxide into the chitosan matrix resulted in enhanced mechanical properties and thermal stability of chitosan biocomposite films. The graphene oxide- and zinc oxide-reinforced chitosan film showed 2527 MPa and 55.72 MPa of Young's modulus and tensile strength, respectively, while neat chitosan showed only 1549 MPa and 37.91 MPa of Young's modulus and tensile strength, respectively. Conversely, the addition of graphene oxide decreased the transmittance, notably in the UV region.Öğe Graphene oxide modified carbon fiber reinforced epoxy composites(Walter De Gruyter Gmbh, 2020) Altin, Yasin; Yilmaz, Hazal; Unsal, Omer Faruk; Bedeloğlu, AyşeThe interfacial interaction between the fiber and matrix is the most important factor which influences the performance of the carbon fiber-epoxy composites. In this study, the graphitic surface of the carbon fibers was modified with graphene oxide nanomaterials by using a spray coating technique which is an easy, cheap, and quick method. The carbon fiber-reinforced epoxy matrix composites were prepared by hand layup technique using neat carbon fibers and 0.5, 1 and 2% by weight graphene oxide (GO) modified carbon fibers. As a result of SEM analysis, it was observed that GO particles were homogeneously coated on the surface of the carbon fibers. Furthermore, Young's modulus increased from 35.14 to 43.40 GPa, tensile strength increased from 436 to 672 MPa, and the elongation at break was maintained around 2% even in only 2% GO addition.Öğe In-Process Recycling of 35% Glass Fiber-Reinforced Polyamide 6,6 Runners: Effects on Thermomechanical Properties and Viability for Diesel Injector Socket Production(Mdpi, 2025) Sahiner, Elif; Altin, YasinSignificant pre-consumer waste in the form of runners is generated during the injection molding of high-performance automotive components, representing both a substantial economic loss and an environmental burden. This study therefore comprehensively evaluated the mechanical recycling of pre-consumer 35% glass fiber-reinforced Polyamide 6,6 (%35GF-PA66) runners for in-process reuse in diesel injector socket production. The effects of blending recycled polymer (RP) at 2.5%, 5%, 10%, and 15% by weight and up to 10 recycling cycles with 15 wt.% RP on the thermal, mechanical, and morphological properties were investigated. Tensile strength slightly decreased (similar to 3% at 10% RP) compared to virgin material, while elongation at break increased with higher RP content. Multiple recycling cycles had minimal impact on tensile strength, and the heat deflection temperature (HDT) remained nearly constant (similar to 0.7 degrees C variation after 10 cycles, within experimental uncertainty). The melt flow index (MFI) increased significantly with successive recycling cycles, indicating molecular weight reduction due to thermomechanical degradation. DSC analysis confirmed stable melting and crystallization temperatures (variation < 1 degrees C), suggesting preserved crystalline structure. SEM analysis revealed increased void formation at the fiber-matrix interface and fiber attrition with successive recycling, correlating with reduced flexural properties. In-process recycling of %35GF-PA66 runners is viable, particularly at <= 15% RP and fewer cycles, offering significant cost savings (e.g., similar to EUR 344,000 annually for a large producer) and environmental benefits.Öğe Poly(vinylidene fluoride) nanofiber-based piezoelectric nanogenerators using reduced graphene oxide/polyaniline(Wiley, 2020) Unsal, Omer Faruk; Altin, Yasin; Bedeloğlu, AyşeRecently, piezoelectric nanogenerators have received great interest as they can convert waste mechanical and radiative energy to electricity and can be used in self-energy generating systems and sensor technologies. In this study, electrospun poly(vinylidene fluoride) (PVDF) nanofiber-based piezoelectric nanogenerators with reduced graphene oxide (rGO), polyaniline (PANI), and PANI-functionalized rGO (rGOPANI) have been developed. Two different types of nanofiber mats were produced: First, rGO- and rGOPANI-doped PVDF nanofiber mats and second, rGO, PANI and rGOPANI-spray-coated PVDF nanofiber mats that have worked as nanogenerators' electrodes. Then, characterizations of samples were performed in terms of piezoelectricity, Fourier transform infrared (FTIR) spectrophotometric, X-ray diffractions (XRD), and scanning electron microscopy analyses. FTIR and XRD results confirmed that piezoelectric beta-crystalline phase of PVDF occurred after the electrospinning process. Besides, maximum output voltages were obtained as 7.84 and 10.60 V for rGO-doped PVDF and rGOPANI-coated PVDF nanofiber mats, respectively. As a result, the doped nanofibers were found to be more successful due to the higher device accuracy in sensor technologies compared with spray-coated samples. However, spray-coating method proved to be more suitable technique for the production of nanogenerators on an industrial scale in terms of fast and large-scale applicability. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48517.Öğe Polyimide-coated fabrics with multifunctional properties: Flame retardant, UV protective, and water proof(Wiley, 2019) Hicyilmaz, Ayse Sezer; Altin, Yasin; Bedeloğlu, AyşeMultifunctional technical textiles are of great interest both by industry and academia and these products are considered as high value-added products that contribute to the economies of countries. In this study, polyamic acid (PAA) was synthesized through polycondensation of pyromellitic dianhydride (PMDA) and 4,4 '-oxydianiline (ODA) in dimethyl acetamide (DMAc) at low temperature. Then, PAA was coated onto woven cotton and polyester fabric by padding technique. Finally, polyimide (PI)-coated multifunctional cotton and polyester fabrics were obtained by an easy coating technique and low-temperature imidization. Thus, low cost, easily accessible and widely used cotton and polyester fabrics were converted to high-performance textile products, which are flame retardant, UV protective, acid resistant, and waterproof. The chemical, thermal, morphological, optical, mechanical, wettability, chemical resistance, and flame retardancy properties of developed fabrics were investigated. Optical results showed that both PI-coated cotton and polyester fabrics are UV-A protective compared to noncoated fabrics. Moreover, PI-coated samples have high contact angles which are 111.43 degrees and 113.40 degrees for PI-coated cotton (PI-c-C) and PI-coated polyester (PI-c-PET), respectively. Young's modulus of PI-c-PET fabrics increased four times more than noncoated polyester fabric. PI coating changed the burning behavior of both cotton and polyester fabrics in a positive way. All the test results showed that these developed multifunctional textile products might find an application in different industrial areas such as automotive, aerospace, protective clothing, and so on due to easy and inexpensive production techniques and also superior properties. (c) 2019 Wiley Periodicals, Inc.Öğe Preparation and characterization of hybrid PLA biocomposites reinforced by wood and silane treated basalt fibers or compatibilized by maleic anhydride-grafted polypropylene (MAPP)(Wiley, 2024) Ermeydan, Mahmut Ali; Aykanat, Onur; Altin, YasinIn this study, basalt and/or beech wood fibers were treated with vinyltrimethoxysilane or compatibilized by maleic anhydride- grafted polypropylene (MAPP) to produce hybrid polylactic acid (PLA) biocomposites. Twin-screw extruder was used to produce biocomposites, following by a hot press to form samples. Physical and mechanical properties of composites that were produced from both treated and untreated fibers were compared. Chemical, morphological, and thermal analysis of biocomposites were analyzed with TGA, FTIR and SEM, respectively. The results showed that silane treated basalt/wood fiber reinforced PLA (PBWS) and silane treated basalt reinforced PLA (PBS) have significantly better flexural strength than neat PLA. Besides, basalt reinforced bio-composites except PBW3 and PBWM variations have significantly superior impact strength than neat PLA. Utilization of compatibilizers also reduced thickness swelling and water uptake features of biocomposites. All the above experimental data showed that the utilization of silane compatibilizer has better impact on properties than MAPP for such wood/basalt hybrid composite.Öğe Reduction of graphene oxide thin films using a stepwise thermal annealing assisted by L-ascorbic acid(Elsevier Science Sa, 2019) Tas, Mahmut; Altin, Yasin; Bedeloğlu, AyşeIn this study, an environmental and economical multi-step reduction method has been developed for the reduction of graphene oxide thin films more efficiently. Within the scope of the method, the graphene oxide films produced were subjected to the process of chemical reduction with L-ascorbic acid (Vitamin C) as the first step and then to the process of thermal reduction that can be performed through progressive thermal annealing without any need for special atmospheric conditions as the second step. In addition, the impact of L-ascorbic acid solutions with different molarities (5, 25, 50, 100, 200, 400 and 800 mM) on the conductivity of the reduced graphene oxide produced was examined and compared with hydrazine hydrate for the same concentrations. Besides, the impact of different thermal annealing temperatures (70 degrees C, 120 degrees C and 300 degrees C) and the process of intermediate drying on the conductivity of the reduced graphene oxide thin films were investigated. The results show that the graphene oxide thin films were best reduced through 800 mM L-ascorbic acid and progressive thermal annealing combination (at 70 degrees C, 120 degrees C and 300 degrees C respectively) and that 13.2 k Omega/sq. surface resistivity was achieved and that the intermediate heating at 120 degrees C made at least 10% positive contribution to this.Öğe Solution-processed transparent conducting electrodes with graphene, silver nanowires and PEDOT:PSS as alternative to ITO(Elsevier Science Sa, 2016) Altin, Yasin; Tas, Mahmut; Borazan, Ismail; Demir, Ali; Bedeloğlu, AyşeNovel transparent electrodes, including graphene, silver nanowires (AgNWs) and poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) serving as the low-cost and flexible alternative to indium tin oxide (ITO) are of interest to the organic electronic industry in recent years. In this paper, transparent, flexible and conductive nanocomposite electrodes were fabricated by using different combinations of graphene, AgNWs, PEDOT:PSS materials via spin coating technique. Optical, morphological and electrical properties of solution-processed electrodes were characterized. Transparent conductive electrode (TCE) based on PEDOT:PSS/AgNW/graphene construction exhibited 216.67 Omega/sq sheet resistance with-83% transparency. Additionally, after 100 cycles of bending, the sheet resistance of PEDOT:PSS/AgNW/graphene electrode on the flexible polyethylene terephthalate (PET) substrate was found to be about 223 Omega/sq, while conventional ITO-coated PET substrate exhibited 83,050 Omega/sq resistance, which was about 400 times more than that of resistance before bending. Optical and electrical measurements showed that obtained nanocomposite electrodes may be promising alternatives to ITO to be used in flexible optoelectronic devices. (C) 2016 Elsevier B.V. All rights reserved.Öğe Synthesis and characterizations of nanohybrids based on amino silane-graphene oxide decorated by zirconium oxide nanoparticles(Elsevier Science Sa, 2024) Zerguine, Narimene; Altin, Yasin; Dahoun, Abdesselam; Bouhelal, SaidThis study aims to synthesize graphene oxide using the modified Hummers method and subsequently functionalize the surface of graphene oxide with amino silane N-(b-aminoethyl)-c-aminopropyltrimethoxysilane (AEAPTMS), resulting in silane-graphene oxide (SGO). The surface of SGO is then decorated with zirconium oxide (ZrO2) nanoparticles, generating SGO-ZrO2 nanohybrids. All the synthetized materials GO, SGO and SGOZrO2 were subjected to various characterization techniques, including Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Thermogravimetric analysis (TGA), Zeta potential measurement and Scanning electron microscope (SEM). The results revealed that GO nanosheets were decorated with ZrO2 nanoparticles through covalent bonding with AEAPTMS.Öğe Tensile behavior of C/GFRP-steel hybrid rebars: Effect of volume fraction and helical angle with a proposed analytical model(Elsevier, 2026) Senaysoy, Safa; Yilmaz, Ayten Nur Yuksel; Bedeloglu, Ayse; Altin, Yasin; Sakcali, Gokhan BarisThis study examines the tensile properties of hybrid rebars consisting of a steel core wrapped with layers of Carbon Fiber-Reinforced Polymer (CFRP) or Glass Fiber-Reinforced Polymer (GFRP). The mechanical performance of the Steel-FRP composite bars (SFCBs) was evaluated through axial tensile tests considering two primary parameters: (i) the longitudinal FRP volume fractions (33 %, 40 %, and 47 %) and (ii) the helical wrapping angles (0 degrees, 30 degrees, and 60 degrees). Although SFCBs have gained increasing attention as an alternative to fully FRP or conventional steel reinforcement, the combined influence of fiber volume fraction and helical orientation on their tensile response has not been clearly established. Experimental findings demonstrated the influence of fiber volume fraction and helical angle on the tensile properties of SFCBs. Specimens coated with carbon exhibited greater strength than those coated with glass, especially at larger wrapping angles, while the glass-coated SFCB specimens demonstrated a wider range of deformation capability. The specimen with a 47 % volumetric fraction and a 60 degrees helical wrap exhibited a 21.8 % increase in yield stress compared with that of the steel bar, whereas its glass-fiber counterpart exhibited a 15.9 % increase. Maximum strength was significantly higher in carbon-SFCB rebars than in glass-SFCB ones. In contrast, glass-SFCB rebars showed 59 % higher ultimate strain. As the volume fraction increased, the influence of the helical angle on ultimate strength decreased. Increasing the helical angle from 0 degrees to 60 degrees enhanced the ultimate strength by up to 32 % in carbon-SFCBs and approximately 12 % in glass-SFCBs at a 33 % volume fraction. An analytical model was proposed to predict a five-zone stress-strain behavior, taking into account the effects of volumetric fraction and helical angle. The proposed model effectively replicated the stress-strain patterns of hybrid rebars in every zone with a satisfactory level of accuracy. Generally, the calculated mean absolute percentage errors for key mechanical parameters such as initial stiffness, yield stress, and fiber-contributed stiffness were below 15 %. This study offers a practical framework for designing SFCBs with customised mechanical properties for sophisticated RC applications.Öğe Textile-Based Flexible Supercapacitors(CRC Press, 2022) Altin, Yasin; Çelik Bedeloğlu, AyşeWith the increase in smart and wearable electronic applications, it has become important to meet the energy demands of these products with flexible and wearable energy storage technologies. Conventional energy storage techniques have difficulty meeting critical requirements, such as flexibility and safety, for wearable electronics applications. Among the textile-based energy storage applications, flexible textile-based supercapacitors stand out due to their advantages, which include flexibility, light in weight, environmentally friendly, long cycle life, and fast charge/discharge. Carbon-based materials (activated carbon, graphene, carbon nanotube, carbon nanofiber, etc.), metal oxides/nitrides/sulfides, conductive polymers (polyaniline, polythiophene, polypyrrole, PEDOT: PSS, etc.), and their combinations are used as electrode materials in supercapacitor applications. Textile-based supercapacitors are developed both by spinning/drawing these electrode materials into a textile form, such as graphene yarn, carbon nanotube yarn, etc., and by applying them on various textile substrates. In this chapter, materials used in textile-based supercapacitors, application techniques of these materials, and textile-based supercapacitor forms are discussed in detail. © 2022 selection and editorial matter,[Ram K. Gupta, Tuan Anh Nguyen; individual chapters, the contributors.
