Browsing by Author "Yar, Adem"

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Citation - WoS: 47
Citation - Scopus: 47
A Biocompatible, Eco-Friendly, and High-Performance Triboelectric Nanogenerator Based on Sepiolite, Bentonite, and Kaolin Decorated Chitosan Composite Film
(Elsevier, 2023) Yar, Adem; Okbaz, Abdulkerim; Parlayici, Serife
Recent advancements in triboelectric nanogenerators (TENGs) have primarily focused on improving power conversion and generation efficiency. However, challenges still exist in developing TENGs that are affordable and biocompatible. Chitosan, an abundant natural biopolymer derived from marine crustacean shells, and natural clays offer exciting possibilities for developing cost-effective and biodegradable TENG applications. In this study, we present the development of biocompatible and eco-friendly TENGs by incorporating clay-based compounds as natural fillers into chitosan. To construct chitosan/clay-based biocomposite TENGs, we have introduced sepio-lite, bentonite, and kaolin, as natural additives, into the chitosan biopolymer matrix. Decorating chitosan with natural clays improves the triboelectric properties of the TENGs, which in turn enhances the output voltage and significantly boosts the electric power density. Chitosan-based TENGs with 3 wt% sepiolite, 1 wt% bentonite, and 1 wt% kaolin demonstrate open circuit voltages of 863, 996, and 963 V, respectively. Moreover, when compared to pure chitosan-based TENG, the chitosan-based TENGs with 3 wt% sepiolite, 1 wt% bentonite, and 1 wt% kaolin show a maximum output peak power increase of 19, 54.4, and 32.6%, respectively. At 1.1 M omega load resistance, the maximum peak electric power densities of 20.4, 26.5, and 22.8 W/m2 are reached for chitosan-based TENGs with 3 wt% sepiolite, 1 wt% bentonite, and 1 wt% kaolin, respectively. Furthermore, we analyzed the surface potential, morphology, roughness, and dielectric constant of chitosan/clay composites to understand the relationship between them and electrical performance. The results demonstrate that the output performances of the chitosan/clay-based TENGs are quite high. TENGs made of biocompatible materials may not only pave the way for the production of environmentally friendly, cost-effective, and efficient TENGs for self-powered nano -systems and biomedical devices but may also shed light on new technologies utilizing natural materials.
Citation - WoS: 27
Citation - Scopus: 32
Carbon Nanotubes/ Polyacrylonitrile Composite Nanofiber Mats for Highly Efficient Dye Adsorption
(Elsevier, 2022) Yar, Adem; Parlayıcı, Şerife
Nanofibers have unique advantages, such as high porosity and large specific surface area. Therefore, they are promising adsorption materials for the efficient removal of dyes from dyeing effluents. However, regulating adsorption properties poses significant challenges. This study incorporated different quantities of carbon nanotubes (CNT) into the polyacrylonitrile (PAN) polymer to fabricate nanofibers to address those challenges. PANnf, CNTs (3 wt%) doped PAN nanofibers (PAN3CNTnf), and CNTs (5 wt%) doped PAN nanofibers (PAN5CNTnf) were used to remove Methylene blue (MB), Malachite green (MG), and Methyl violet (MV) from different concentrations of aqueous solutions. The study examined the effect of pH, temperature, adsorbent material, and time on adsorption capacity, and applied adsorption isotherms. The maximum adsorption capacity (qm) of the dyestuff Langmuir model was 128.21 mg/g for PANnf:MB, 138.89 for PANnf:MG, 88.50 for PANnf:MV, 172.41 for PAN3CNTnf:MB, 212.77 for PAN3CNTnf:MG, 175.44 for PAN3CNTnf:MV, 158.73 for PAN5CNTnf/MB, 188.68 for PAN5CNTnf:MG, and 114.94 for PAN5CNTnf:MV. Adsorption Gibbs free energy, enthalpy, and entropy were also evaluated using adsorption isotherms at various temperatures. The negative Delta G values show that adsorption occurs spontaneously. Pseudo-first-order kinetic (PFOK) and pseudo-second-order kinetic (PSOK) models were employed to determine adsorption kinetics. The results revealed that the PSOK model agreed better with the experimental data. The experimental outcomes showed that PANnf, PAN3CNTnf, and PAN5CNTnf nanofibers were good choices for adsorbing MB, MG, and MV, which shines a light on the fabrication of multifunctional nanofiber for dye applications.
Citation - WoS: 12
Citation - Scopus: 11
Combined Effect of Fiber Hybridization and Matrix Modification on Mechanical Properties of Polymer Composites
(Sage Publications Ltd, 2023) Demir, Okan; Yar, Adem; Eskizeybek, Volkan; Avci, Ahmet
Glass/carbon fiber reinforced hybrid composites are great candidates for wind turbine blade manufacturers to make larger blades. Variation of stacking sequences ensures design freedom to the composite engineers to optimize the composite structure's mechanical performance. On the other hand, matrix modification of polymer composites with nanoparticles is also of interest to introduce multifunctional properties. This research aims to scrutinize the influence of simultaneous fiber hybridization and matrix modification on polymer composites' tensile, flexural, and low-velocity impact properties. Hybrid glass/carbon epoxy composites and hybrid glass/carbon/multi-walled carbon nanotube (MWCNT) multiscale polymer composites of stacking sequences [GCGCGC](S), [CGCGCG](S), and [G(6)C(6)] were manufactured. Fiber hybridization dramatically improved tensile strength between 51% and 76% compared to glass fiber composite. Depending on the stacking sequence, the flexural strength of the hybrid composites was improved between 10% and 16% concerning carbon fiber composite. With the introduction of MWCNTs, a slight increase in the tensile strength for unsymmetrical hybrid composites by around 5% and decreases by 7% for symmetrical ones were observed. Similar behavior was seen for bending characteristics. Additionally, low-velocity impact tests showed that it is achievable to bring greater impact peak forces up to 70% for hybrid composites than carbon fiber epoxy composites. MWCNTs modification of the matrix restrained the impact damage propagation, as proved by C-scan analysis.
Citation - WoS: 6
Citation - Scopus: 5
Effects of Low-Velocity Impact on Vibration Behaviors of Polyamide Fiber-Reinforced Composites
(Springer Heidelberg, 2022) Coskun, Taner; Yar, Adem; Demir, Okan; Sahin, Ömer Sinan
Fabric and resin materials, fiber orientations, volume fraction and knitting patterns are highly effective for the mechanical and dynamic properties of the composite materials. These materials can be subjected to impact loads at various energy levels depending on their application areas, and thus causes the material properties to change. Therefore, experimental studies have been carried out to determine the dynamic properties for the polyamide fiber-reinforced epoxy composites, which can be defined as a novel composite material variation, before and after low-velocity impact. In this context, the composite specimens were subjected to one and two repeated low-velocity impacts under 25.2 J constant energy. Apart from that experimental vibration tests were conducted under free-free boundary conditions to determine how dynamic properties such as natural frequency, flexural modulus, and specific damping capacity will change with the consequent distortion in the structural integrity. For the current study, at least three samples were subjected to the experimental tests to verify obtained results, and standard deviations revealed that results were reliable and repeatable. As a consequence of the current study, it has been concluded that the composite specimens have high matrix volume fractions due to the knitting architecture of the polyamide fabrics. Moreover, since the polyamide fabrics have spacious mesh weave, an improvement for the damping properties has been achieved due to the increased fiber-resin interface. It has been observed that polyamide composite specimens exhibited approximately 11.5% specific damping capacity, and had relatively higher damping properties compared to the conventional materials. It was also revealed that the degradation in the specific damping capacities was observed by virtue of the low-velocity impact but it was not significantly effective on the dynamic properties due to the limited damage area. Additionally, it was found that polyamide fiber-reinforced composites can be used as the optimum material for the application areas in which high damping and impact resistance are required.
Citation - WoS: 13
Citation - Scopus: 16
The Influences of Low-Velocity Impact Loading on the Vibration Responses of the Carbon/Glass Fiber-Reinforced Epoxy Composites Interleaved With Various Non-Woven Thermoplastic Veils
(Wiley, 2023) Tarih, Yavuz Selim; Coşkun, Taner; Yar, Adem; Gündoğdu, Ömer; Şahin, Ömer Sinan
Time-dependent variable stresses that occur in composites subjected to mechanical and dynamic loads have devastating impacts on the material properties. Since these stresses reduce the service life, it is critical to detect and enhance structural responses before and after dynamic loadings. Therefore, the present study aimed to increase the toughness and delamination resistance of the conventional fiber-reinforced composites by means of thermoplastic veil interleaves, thereby improving the vibration responses both before and after low-velocity impact (LVI). In this context, carbon fiber (CF) and glass fiber (GF) reinforced epoxy composites interleaved with five different thermoplastic veils as Polyamide (PA), Polyetheretherketone (PEEK), Polyetherimide (PEI), Polyimide (PI) and Poly-Phenylene Sulphide (PPS) were manufactured, and machined in accordance with the LVI standard. Composite specimens were subjected to the LVI tests, and then vibration tests were carried out for the non-impacted and impacted specimens to determine dynamic properties. As a result, although thermoplastic veils generally have favorable effects on damping ratios of the GF composites, it has been revealed that these veils other than PPS and PI cause deterioration in CF composites. On the other hand, since vibration reduction depends on inherent damping and structural stiffness, this study also examined the storage-to-loss modulus ratios which denote the loss factors. In this respect, it was discovered that, while PPS, PEEK, PA, and PI thermoplastic veils included among the GF laminates ascend the loss factors of composites, only PI and PPS thermoplastic veils were shown to be positively effective in CF laminates. Moreover, CF and GF reinforced composites interleaved with thermoplastic veils generally exhibited higher natural frequency and lower damping ratio compared to the entirely CF or GF laminated composites. These results show that composite specimens gained bending stiffness due to local deformation hardening, and improved dynamic properties thanks to thermoplastic veil interleaved was attributed to increased toughness and delamination resistance.
Citation - WoS: 1
Citation - Scopus: 1
Influences of Various Thermoplastic Veil Interleaves Upon Carbon Fiber-Reinforced Composites Subjected To Low-Velocity Impact
(SAGE Publications Ltd, 2025) Coşkun, Taner; Tarih, Ömer Sinan; Yar, Adem; Gündoğdu, Ömer; Sahin, Ömer Sinan
Throughout their service life, composite materials may be subjected to impact loads, which can result in some damage mechanisms that cause degradation in mechanical and dynamic responses. Especially matrix-induced cracks and delamination can have significant effects on the final properties, and cause serious problems if the necessary precautions are not taken. In the current study, Carbon Fiber-Reinforced Polymer (CFRP) composites interleaved with Fine Glass (FG), Polyetherimide (PEI), Polyetheretherketone (PEEK), Polyimide (PI) and Poly-Phenylene Sulphide (PPS) thermoplastic veils were fabricated, and exposed to LVI tests under 25.2 J constant impact energy to determine how veils affect the dynamic properties. The selected veils are commercially available materials and are used for various purposes. In this regard, it was aimed to examine the usability of these commercially available veils as interlayers and to examine the impacts of the veils used as interlayers on the LVI characteristic of CFRP composites. According to the present study, it was found that veil interleaves significantly affect the composite stiffness, and accordingly, relevant LVI responses such as total impulse, bending stiffness, interaction times etc. For instance, approximately 21.2% reduction in the peak displacement and 73.23% increment in the bending stiffness were observed due to FG veil interleaves. On the other hand, when the effects of veil types were examined, the maximum and minimum variations in the LVI responses were observed for the FG and PEI interleaves, respectively, and FG veils were found to be the most effective veil types for the CFRP composites. It was also revealed that veil interleaves strengthen the interlaminar region between plies and delamination resistance, and thereby improved the Delamination Threshold Loads for all configurations. © The Author(s) 2024.
Citation - WoS: 14
Citation - Scopus: 16
Residual Compressive Strength of Polyamide Fiber-Reinforced Epoxy Composites After Low-Velocity Impact
(Wiley, 2023) Coşkun, Taner; Yar, Adem; Demir, Okan; Şahin, Ömer Sinan
In this study, polyamide fibers, which stand out with their excellent plastic deformation and energy absorption capacity, were used as reinforcement materials, and in-house manufactured composite specimens were subjected to low-velocity impact (LVI), compression after impact (CAI) and tensile tests. Within this scope, one and two repeated drop tests were performed under 3 m/s velocity to determine LVI responses and how impact number affects the dynamic properties. CAI tests were also performed at a 1 mm/min crosshead speed, and mechanical properties for non-impacted, one-impacted, and two-impacted specimens were determined. As a result of the outstanding plastic deformation capacity of thermoplastic fabrics, it is concluded that polyamide composites exhibited quite large strains. Furthermore, it was understood from the tensile responses that tensile stresses were carried by the thermoplastic fibers in two different regimes and significantly high toughness was obtained. Moreover, reductions in the maximum compression loads, critical buckling loads and axial stiffness were observed due to degradation in structural integrity after impact loads. Additionally, the utilization of recyclable thermoplastic polyamide fibers as reinforcement material instead of conventional reinforcement materials such as carbon and glass fibers provide more environmentally friendly products.
Citation - WoS: 16
Citation - Scopus: 20
Zno-Tio2 Doped Polyacrylonitrile Nano Fiber-Mat for Elimination of Cr (vi) From Polluted Water
(SPRINGER INTERNATIONAL PUBLISHING AG, 2019) Parlayıcı, Şerife; Yar, Adem; Pehlivan, Erol; Avcı, Ahmet
PAN nanofiber-Mat (n-fib@Mat), PAN/ZnO n-fib@Mat, and PAN/ZnO-TiO2 n-fib@Mat were prepared via electrospinning method. Their high adsorption capacities against dissolved Cr (VI) ions make them as super adsorbents for water treatment The structure of n-fib@Mat was investigated using XRD, FTIR, SEM, and TEM techniques. The effects of selected parameters such as contact time, initial concentration, and n-fib@Mat amount were assessed in a fixed bed reactor. It was found that the adsorption capacities of PAN n-fib@Mat, PAN/ZnO nfib@Mat, and PAN/ZnO-TiO(2)n-fib@Mat were pH-dependent and the optimal pH value was between 2.1 and 2.2. The adsorption was rapid, and the equilibrium was reached within 240 min to remove of Cr (VI) ions for PAN/ZnOTiO2 n-fib@Mat and 360 min for PAN n-fib@Mat and PAN-ZnO n-fib@Mat. Langmuir isotherms model is preferred for PAN n-fib@Mat, PAN-ZnO n-fib@Mat, and PAN/ZnO-TiO2 n-fib@Mat for Cr (VI) adsorption. The equilibrium adsorption capacities are 153.85 mg/g, 234.52 mg/g, and 333.43 mg/g for PAN n-fib@Mat, PAN/ZnO n-fib@Mat, and PAN/ZnO-TiO(2 )n-fib@Mat for Cr (VI), respectively. The produced n-fib@Mat showed excellent removal ability for Cr (VI). The adsorption kinetic was obeyed pseudo-second-order reaction rate.