Yazar "Yunus, Doruk Erdem" seçeneğine göre listele
Listeleniyor 1 - 9 / 9
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe An investigation of PLLA hybrid stent design to overcome thick strut problems(Pergamon-Elsevier Science Ltd, 2024) Erdogus, Hakan Burcin; Yunus, Doruk ErdemBiodegradable polymer-based stents simultaneously provide scaffolding, drug release, and biodegradation to eliminate chronic inflammation. The most important factors hindering the wide use of these stents are thick struts, low radial strength, and large footprints formed on the inner wall of the artery as a result of stent expansion. Negative Poisson's Ratio (NPR), also known as the Auxetic design, has shown great potential to provide radial strength with less strut thickness. However, a detailed mechanical evaluation proving improvement in stent performance parameters is not available in the literature. In this study, the performance parameters of two stent designs based on the Auxetic geometry with PLLA were analyzed under in-vivo conditions using an in-silico model consisting of the artery, crimper, and expander FE model. For this purpose, one design utilizes Auxetic unit cell, which is already available in the literature, while the other uses a newly proposed Hybrid design combining Auxetic and Chevron type geometries. Additionally, a specially heated coaxial balloon-catheter system was considered as a deployment tool between glass transition and body temperature, and carried out for thin-strut stent simulations. The Hybrid design is shown to resolve the foreshortening problem of Auxetic design and collapse pressure of commercial PLLA stents. In this present study validates the potential of Hybrid design to overcome problems for polymer-based biodegradable stents.Öğe Electromagnetic interference shielding, mechanical, and flame retardant behaviors of Ti3C2Tx-MXene/glass fabric epoxy hybrid composites(Elsevier Science Sa, 2024) Yilmaz, Ayten Nur Yuksel; Bedeloglu, Ayse Celik; Yunus, Doruk ErdemThis study investigates the manufacturability and electromagnetic shielding effectiveness (EMI-SE) of Ti3C2Tx/ MXene-coated glass fabric laminated composites for aerospace applications. MXene-coated fabrics were produced using a dip-coating method. The effects of varying dipping counts (5 and 10) and different configurations of fabric arrangements on the EMI-SE of the composites in the X-band range (8.2-12.4 GHz) were investigated. Glass fabrics with 5 and 10 dips showed average surface resistances of 38.56 Omega/sq and 23.17 Omega/sq, respectively. In both the 5- and 10-dip composite sets, the total EMI-SE increased with the number of MXene-coated glass fabric layers in the composite. The 5MXC5 and 10MXC5 specimens, with conductive fabric in all layers, had average total shielding effectiveness (SET) of -18.75 dB and -23.21 dB, respectively. These values are 147.05 % and 205.80 % higher than the neat glass fiber-epoxy composite (C1). Flammability, bending, ILSS, and hardness tests were conducted on these composites. Increasing the MXene content reduced the burning rate, with 10MXC5 exhibiting a 26.31 % lower burning rate compared to C1. However, higher MXene content slightly decreased bending and ILSS values. Optical microscope examination of the fracture surfaces revealed that this decrease was due to delamination damage.Öğe Enhancing mechanical and flame retardant characteristics of glass fiber-epoxy laminated composites through MXene and functionalized-MXene integration(Elsevier, 2024) Yilmaz, Ayten Nur Yuksel; Bedeloglu, Ayse Celik; Yunus, Doruk ErdemMXene, a 2D transition metal carbide and nitride with graphene-like layered structures, has become one of the preferred choice for nano-reinforcement in polymer matrix composites in recent years due to its outstanding properties such as specific surface area, excellent thermal and mechanical characteristics, and high conductivity. In this study, the glass fiber-epoxy laminated composites reinforced with Ti3C2Tx-MXene (M)/ functionalizedMXene (FM) were produced using the hand lay-up procedure followed by vacuum bagging process. The effects of varying filler amounts (0.125, 0.25, 0.375, and 0.5%) on the mechanical and flame retardancy properties of glass fiber-epoxy composites were examined. In both M and FM reinforced composites, the highest values of mechanical strengths were obtained with a 0.25% filler, while a decrease in mechanical strengths was observed beyond this reinforcement amount. The 0.25 wt% FM-reinforced composite exhibited 19.21%, 27.55%, and 12.40% higher tensile, flexural, and interlaminar shear strengths (ILSS) than the pristine glass fiber-epoxy composite (N-C). Post-test analysis revealed the presence of matrix cracks, fiber breakage, and fiber pull-out damages were observed on the surfaces of composite samples. The flame retardant properties of the composites were enhanced with the addition of MXene reinforcement, and 0.5FM-C exhibited 25.50% lower burning rate than N-C.Öğe Enhancing topology optimization for multi-objective using sheet-based TPMS and CFRP: an ANN and NSGA-II approach(Emerald Group Publishing Ltd, 2025) Kofoglu, Muhammed; Yunus, Doruk ErdemPurpose - This study aims to enhance a decision-support system that offers optimum solutions to obtain the optimal topology using a sheet-based triply periodic minimal surface (TPMS) and carbon fiber-reinforced polymer (CFRP). Design/methodology/approach - Within the scope of this study, the mechanical responses resulted by changing the orientation, type, size, relative density and graded relative density of the unit cells likewise the number of composite layers were examined. Wrapped around the sheetbased TPMSs, the CFRP allowed the lattices to absorb more energy during deformation, maintaining their shape integrity. An artificial neural network (ANN) was trained to reveal the relationships between the design parameters and mechanical properties. Findings - According to SHAP values, the highest significance in the ANN model was determined as mass, graded relative density, cell size and number of composite layers. The significance of mass was greater than the sum of the importance of the other design parameters. An approximately linear relationship existed between the design parameters and peak crushing force, mean crushing force, energy absorption and plateau stresses, whereas specific energy absorption (SEA) and crushing load efficiency (CLE) had a complex relationship. Originality/value - The non-dominated sorting genetic algorithm-II (NSGA-II) was used to find the optimum solution from the complex relationship between the design parameters and SEA and CLE. Design parameters for optimum crashworthiness were determined using NSGA-II, a heuristic optimization method using an ANN as the objective function.Öğe Lattice optimization of fiber-reinforced polymer parts fabricated by additive manufacturing: the impact of Bezier curve order on mechanical properties(Emerald Group Publishing Ltd, 2024) Kofoglu, Muhammed; Yunus, Doruk Erdem; Ercan, NecatiPurposeLattice structures are widely used for achieving optimal topology in additive manufacturing. However, the use of different lattices in a single design can result in stress concentrations at the transition points. This study aims to investigate the influence of Bezier curves on mechanical properties during the transformation from one lattice structure to another. It specifically focuses on the transition from a hexagonal to diamond lattice, using Bezier curves of various orders.Design/methodology/approachThe curves were designed by passing them through the same control points for different orders, such as third, fifth and seventh. The samples were sliced for 3D printing, and a tensile test was conducted. Young's modulus and energy absorption abilities were measured to compare the mechanical properties of the models created with Bezier curves for the transformation between hexagonal and diamond models.FindingsThe analysis revealed a gradual change in mechanical properties from the hexagonal to the diamond lattice. Moreover, different orders of Bezier curves exhibited varying mechanical properties during the transformation between the two lattices. As the order of the Bezier curve increased, the mechanical properties smoothly changed from the hexagonal to diamond lattice. This prevented stress concentrations or mechanical behavior mismatch caused by sudden deformations at the transitions between the curves used in the design.Originality/valueThe study's innovative use of Bezier curves of different orders to smoothly transformation between hexagonal and diamond lattices in additive manufacturing offers a practical solution to prevent stress concentrations and mechanical inconsistencies during such design transitions.Öğe Mechanical response of carbon fiber reinforced epoxy composite parts joined with varying bonding techniques for aerospace applications(Elsevier Sci Ltd, 2024) Karaboga, Furkan; Golec, Fatih; Yunus, Doruk Erdem; Toros, Serkan; Oz, YahyaAs a result of the widespread use of composite materials in primary structures of aerospace platforms, composite joining became more crucial. This study addresses the effect of joining methods on the strength of composite joints experimentally, numerically and analytically. Single lap joint shear strengths of carbon fiber reinforced epoxy composite parts joined by mechanical fastening with a pop and solid rivet, secondary bonding with a paste adhesive, co-curing and co-bonding techniques were compared. In addition, the effect of adhesive thicknesses (0.2, 0.4, 0.6, 0.76 mm) on the single lap shear strength was investigated. Carbon fiber reinforced composite (CFRP) samples were produced according to the ASTM 5868 standard. After the production of samples with varying joining methods, single lap shear tests were implemented. Moreover, the interface damage in the composites was examined by use of a scanning electron microscope (SEM) for the purpose of studying the damage mechanism. Fracture mechanisms corresponding with bonding methods were also assessed by examining the fracture surface of the composite samples. Furthermore, results were analyzed by Hypermesh, ABAQUS and ESAComp. For instance, the co-bonded sample with an adhesive film exhibits an experimental shear strength of 24.03 MPa which deviates only 3 % from the numerical expectation.Öğe The effect of MXene on the mechanical and electromagnetic interference shielding features of carbon fabric/epoxy scalable laminated composites(Springer, 2025) Yuksel Yilmaz, Ayten Nur; Bedeloglu, Ayse Celik; Yunus, Doruk ErdemIn this study, the aim was to improve the interfacial properties of carbon fabric-epoxy matrix composites using MXene, a 2D material with superior characteristics, as a reinforcement. To achieve this, carbon fabrics were first surface-activated using concentrated nitric acid, followed by spraying a solution containing MXene in varying weight percentages (0.2%, 0.4%, and 0.8%). Subsequently, epoxy matrix-based laminated composites were fabricated using the vacuum infusion method. The composites were then subjected to tensile, flexural, interlaminar shear strength (ILSS), Mode-I fracture toughness, and electromagnetic interference (EMI) shielding tests. The results showed that the composite reinforced with 0.4% MXene exhibited the highest mechanical performance, demonstrating increases of 12.71%, 12.63%, and 13.13% in flexural strength, ILSS, and tensile strength, respectively, compared to the reference carbon fabric-epoxy composite. Additionally, the Mode-I fracture toughness of this composite was improved by 25.32%. Scanning electron microscopy (SEM) analysis was conducted to examine the fracture regions of the composites and ascertain the underlying damage mechanisms. The increase in the amount of MXene coated on the fabric surface did not create a significant difference in the EMI-SE values of the composites in the X-band range. The total shielding effectiveness values of the CF, ACF, 0.2MX, 0.4MX, and 0.8MX samples were calculated as - 31.13 dB, - 31.39 dB, - 31.45 dB, - 32.77 dB, and - 32.63 dB, respectively. These findings demonstrate that MXene is an effective reinforcement for improving the interfacial properties of laminated composites for scalable production.Öğe Başlıksız(Amer Inst Physics, 2018) Sohrabi, Salman; Tan, Jifu; Yunus, Doruk Erdem; He, Ran; Liu, YalingIsolating cells of interest from a heterogeneous population has been of critical importance in biological studies and clinical applications. In this study, a novel approach is proposed for utilizing an active ciliary system in microfluidic devices to separate particles based on their physical properties. In this approach, the bottom of the microchannel is covered with an equally spaced cilia array of various patterns which is actuated by an external stimuli. 3D simulations are carried out to study cilia-particle interaction and isolation dynamic in a microfluidic channel. It is observed that these elastic hair-like filaments can influence particle's trajectories differently depending on their biophysical properties. This modeling study utilizes immersed boundary method coupled with the lattice Boltzmann method. Soft particles and cilia are implemented through the spring connected network model and point-particle scheme, respectively. It is shown that cilia array with proper stimulation is able to continuously and non-destructively separate cells into subpopulations based on their size, shape, and stiffness. At the end, a design map for fabrication of a programmable microfluidic device capable of isolating various subpopulations of cells is developed. This biocompatible, label-free design can separate cells/soft microparticles with high throughput which can greatly complement existing separation technologies. Published by AIP Publishing.Öğe Başlıksız(SAGE PUBLICATIONS LTD, 2022) Yılmaz, Ayten Nur Yüksel; Yunus, Doruk Erdem; Bedeloğlu, AyşeHybrid composite specimens were produced with stainless steel-acrylic (SSA) and carbon fiber reinforcement in order to achieve ductile behavior compared to CF reinforced epoxy composites. Laminated composites containing CF and SSA fabrics in with different ply configurations were manufactured using vacuum infusion method. In addition, CF fabric was used in two different ply orientations (0-45 degrees). In both the flexural and tensile test results, composites having CF oriented at 0 degrees showed higher strength and modulus but lower strain than composites having CF oriented at 45 degrees. When the number of carbon fiber layers increased, the composites showed high strength and modulus, but low strain. Increasing the number of SSA significantly increased the flexural and tensile strains of laminated composites. After the mechanical tests, the fracture surfaces of the specimens were examined with an optical microscope and matrix cracks, fiber breakage, fiber pull-out and delamination failures were observed.
