WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Article Citation - WoS: 13Citation - Scopus: 16Influence of Recycled Carbon Fiber Addition on the Microstructure and Creep Response of Extruded Az91 Magnesium Alloy(KeAi Communications Co., 2023) Kandemir, Sinan; Bohlen, Jan; Dieringa, HajoIn this study, the recycled short carbon fiber (CF)-reinforced magnesium matrix composites were fabricated using a combination of stir casting and hot extrusion. The objective was to investigate the impact of CF content (2.5 and 5.0 wt.%) and fiber length (100 and 500 µm) on the microstructure, mechanical properties, and creep behavior of AZ91 alloy matrix. The microstructural analysis revealed that the CFs aligned in the extrusion direction resulted in grain and intermetallic refinement within the alloy. In comparison to the unreinforced AZ91 alloy, the composites with 2.5 wt.% CF exhibited an increase in hardness by 16–20% and yield strength by 5–15%, depending on the fiber length, while experiencing a reduction in ductility. When the reinforcement content was increased from 2.5 to 5.0 wt.%, strength values exhibited fluctuations and decline, accompanied by decreased ductility. These divergent outcomes were discussed in relation to fiber length, clustering tendency due to higher reinforcement content, and the presence of interfacial products with micro-cracks at the CF-matrix interface. Tensile creep tests indicated that CFs did not enhance the creep resistance of extruded AZ91 alloy, suggesting that grain boundary sliding is likely the dominant deformation mechanism during creep. © 2023Article Citation - WoS: 15Citation - Scopus: 17Effects of Nanosecond Laser Ablation Parameters on Surface Modification of Carbon Fiber Reinforced Polymer Composites(SAGE Publications, 2023) Martin, Seçkin; İplikçi, Hande; Barışık, Murat; Türkdoğan, Ceren; Yeke, Melisa; Nuhoğlu, Kaan; Esenoğlu, Gözde; Tanoğlu, Metin; Aktaş, Engin; Dehneliler, Serkan; İriş, Mehmet ErdemRemoval of contaminants and top polymer layer from the surface of carbon-fiber-reinforced polymer (CFRP) composites is critical for high-quality adhesive-joining with direct bonding to the reinforcing fiber constituents. Surface treatment with a laser beam provides selective removal of the polymer matrix without damaging the fibers and increasing the wettability. However, inhomogeneous thermal properties of CFRP make control of laser ablation difficult as the laser energy absorbed by the carbon fibers is converted into heat and transmitted through the fiber structures during the laser operation. In this study, the effect of scanning speed and laser power on nanosecond laser surface treatment was characterized by scanning electron microscope images and wetting angle measurements. Low scanning speeds allowed laser energy to be conducted as thermal energy through the fibers, which resulted in less epoxy matrix removal and substantial thermal damage. Low laser power partially degraded the epoxy the surface while the high power damaged the carbon fibers. For the studied CFRP specimens consisting of unidirectional [45/0/?45/90]2s stacking of carbon/epoxy prepregs (HexPly®-M91), 100 mJ/mm2 generated by 10 m/s scanning speed and 30 W power appeared as optimum processing parameters for the complete removal of epoxy matrix from the top surface with mostly undamaged carbon fibers and super hydrophilic surface condition. © The Author(s) 2023.Article Citation - WoS: 14Citation - Scopus: 19Influence of Carbon Nanotube Inclusions To Electrical, Thermal, Physical and Mechanical Behaviors of Carbon-Fiber Abs Composites(Springer, 2022) Akar, Alinda Öykü; Yıldız, Ümit Hakan; Tirkeş, Seha; Tayfun, Ümit; Hacıvelioğlu, FerdaAcrylonitrile–butadiene–styrene (ABS) terpolymer was compounded with short carbon fiber (CF) and carbon nanotube (CNT) using a micro-extruder followed by the injection molding process. Composite samples were fabricated with loading ratios of 20 wt.% CF and 0.1, 0.5 and 1.0 wt.% of CNT. Mechanical, electrical, thermo-mechanical, thermal, melt-flow, and structural investigations of ABS-based composites were conducted by performing tensile, impact, hardness, and wear tests, conductive atomic force microscopy (AFM), dynamic mechanical analysis (DMA), thermal gravimetric analysis (TGA), melt flow rate test (MFR), scanning electron microscopy (SEM) characterization techniques, respectively. According to mechanical test data of resultant composites including tensile and impact test findings, CNT additions led to the remarkable increase in tensile strength and impact resistance for CF reinforced ABS composites. The formation of synergy between CNT nanoparticles and CF was confirmed by electrical conduction results. The conductive path in ABS/CF composite system was achieved by the incorporation of CNT with different loading levels. SEM micrographs of composites proved that CNT nanoparticles exhibited homogeneous dispersion into ABS matrix for lower loadings. Graphical abstract: [Figure not available: see fulltext.].Article Citation - WoS: 11Citation - Scopus: 12Cement Based Strain Sensor: a Step To Smart Concrete(Foundation Cement, Lime, Concrete, 2011) Teomete, Egemen; Erdem, Tahir KemalAccording to a report published in USA, 30% of the bridges in USA were found to be structurally de cient while concrete infrastructures have a state of material deterioration before the design life is reached (1). Earthquakes, material degradations and other environmental effects decrease the performance of the structures. The assessment of structures by structural health monitoring is very important to protect the lives of people. The best decision about a damaged structure after an earthquake can be made by use of structural tests and structural health monitoring. Structural tests and structural health monitoring are important steps in the decision making of asset management for maintenance and repair of infrastructures. The classical sensors (strain gauges, piezo-electric sensors) have low durability, low sensitivity and high cost. The low durability of classical sensors disables long term measurement while their high cost limits the amount of sensors that can be used (2). The addition of carbon ber to cement based material decreases the electrical resistance of the material. By application of load, the electrical resistance of the material changes (3-5).Article Citation - WoS: 31Citation - Scopus: 33Modification of Carbon Fibre/Epoxy Composites by Polyvinyl Alcohol (pva) Based Electrospun Nanofibres(Adcotec Ltd., 2016) Beylergil, Bertan; Tanoğlu, Metin; Aktaş, EnginIn this study, the effects of modifying interlaminar region of unidirectional carbon fibre/epoxy composites by the incorporation of electrospun polyvinyl alcohol (PVA) nanofibres were investigated. PVA nanofibres were directly deposited onto the carbon fabrics by electrospinning method to improve mechanical performance of those composites. The features of the electrospun nanofibres were characterized by microscopy techniques. The unidirectional carbon fibre/epoxy composite laminates with/without PVA nanofibre interlayers were manufactured by vacuum-infusion technique in a [0]4 configuration. Tensile, three-point bending, compression, Charpy-impact and Mode-I fracture toughness tests (Double Cantilever Beam (DCB)) were carried out in accordance with ASTM standards to evaluate mechanical performance of the composites. Scanning electron microscopy (SEM) observations were made on the specimens to evaluate microstructural features. It was observed that the carbon fabrics were successfully coated with a thin layer of PVA nanofibres by electrospinning technique. The results showed that P VA nanofibres improve the mechanical properties of unidirectional carbon/epoxy composite laminates when subjected to in-plane loading. On the other hand, PVA nanofibres slightly reduced the mode-I fracture toughness values although they led to more stable crack propagation.