Browsing by Author "Kosedag, Ertan"

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Copula-Based Data Augmentation and Machine Learning for Predicting Tensile Strength of 3D-Printed PLA Under Anisotropic Conditions
(Wiley, 2025) Saylik, Ahmet; Kosedag, Ertan; Etem, Taha
In this study, 48 polylactic acid (PLA) samples were produced via 3D printing, incorporating four infill geometries (gyroid, lattice, honeycomb, and linear), four infill rates (15%-60%), and three printing directions (x, y, z). Tensile testing revealed anisotropic mechanical behavior, with the x-direction consistently outperforming y- and z-directions due to layer adhesion dynamics. A machine learning framework leveraging copula-based data augmentation was developed to predict tensile strength at untested infill rates. The framework employed least squares regression, support vector machines (SVM), Gaussian process regression (GPR), and artificial neural networks (ANNs), augmented with 20,000 synthetic data points to enhance model robustness. Results demonstrated that gyroid geometry in the x-direction achieved the highest tensile strength (53.4 MPa at 60% infill), while Lattice patterns underperformed. Data augmentation improved prediction accuracy across all models, with SVM achieving the lowest RMSE (1.53 MPa) and R2 values exceeding 0.87. This study highlights the critical interplay of infill parameters, directional anisotropy, and machine learning in optimizing 3D-printed PLA components for industrial applications, offering a data-driven pathway to reduce experimental costs and accelerate material design.
Effect of Artificial Aging on 3-Point Bending Behavior of Glass Fiber/Epoxy Composites
(Sage Publications Ltd, 2023) Kosedag, Ertan
This study looked into how artificial aging affected the mechanical behavior of composites made of glass fiber reinforced polymer (GFRP). In this context, GFRP composites were produced by vacuum infusion method and artificially aged in the aging cabinet. Three different composite specimen types were tested. These are unaged samples aged 750 h and aged 1500 h. Three-point bending tests were performed to determine the mechanical properties. The absorbed energies of the samples were determined and the maximum bending stresses were calculated. The maximum contact force and sample displacements were also determined. In addition, the damage areas of the samples were examined optically and the changes that occurred with the aging time were determined. Finally, SEM images were taken to observe the changes in the internal structure of the aging and non-aging samples. According to results, as the sample aged, a decrease was observed in the energy values absorbed by the composite samples. In addition, as the aging time increased, it was determined that there was a spread in the damage area and more visible fiber breaks occurred. The increase in the aging time caused a decrease in the stiffness of the composite specimen, worsened its mechanical properties, and increased matrix damage.
The Effect of Artificial Aging on the Impact Behavior of Sic Nanoparticle-Glass Fiber-Reinforced Polymer Matrix Composites
(Wiley, 2022) Kosedag, Ertan; Caliskan, Umut; Ekici, Recep
The low-velocity impact behavior of SiC nanoparticle-glass fiber-reinforced polymer matrix composites (PMC) in terms of different weight fraction of nanoparticle, artificial aging time, and impact energy was investigated in this article. In this context, silicon carbide (SiC-70 nm) ceramic nanoparticle in weight fractions of 0%, 0.1%, 1%, 2%, 3% filled glass fiber-reinforced PMCs were produced by vacuum infusion technique. The specimens were artificially aged in 0, 750, and 1500 h, 85% relative humidity and 70 degrees C in air conditioning cabinet. The after-impact damage regions were obtained using ultrasonic scanning technique for three different impact energies of 10, 20, and 30 J. The weight of specimens was measured at certain periods during aging and the weight change was examined. As the weight fraction and aging time were increased, the impact resistance of specimens decreased. At the beginning of aging period, the weight of specimens increased; however, the increase in weight decreased over time. Ultrasonic scanning results showed that the damage geometry changed and increasing discontinuity with increasing weight fraction and artificial aging time.
The Effect of Halloysite Nanotubes Reinforced Epoxy Filler on the Crushing Behavior of Aluminum Tubes
(Wiley, 2024) Kosedag, Ertan
Crash box is one of the equipment to minimize the damage that may occur during an accident in vehicles. Many studies are conducted to improve the performance of crash boxes. Some of these studies were aimed at filling thin-walled crash boxes. Halloysite nanotubes (HNT) were used as filling material in this study. HNT can be found in nature and is in nanotube structure by nature. For this reason, it is inexpensive compared to other nanotubes like carbon nanotube. Within the scope of the study, epoxy-based mixtures with 0%, 5%, 10%, and 15% HNT were prepared and filled into aluminum tubes. The powders used were similar to 20-100 nm in size and in the form of cylindrical tubes. Investigated were the effects of the HNT ratio and the thin-walled aluminum construction. Nine diverse types of specimens were created. The vacuuming principle was used as the production method. The reason for this is to minimize the air bubbles that may occur during mixing. The effect of aluminum tube and HNT ratio on energy absorption and mechanical strength was investigated. For this, quasi-static tests were conducted. The absorbed energies of the specimens were determined by integrating the acquired contact force-displacement curves, and the specific absorbed energy was determined by dividing the absorbed energy by the specimen weights. SEM images were taken for internal structure characterization. In addition, FTIR analysis was performed to determine whether the composite was cured. According to the results obtained, the mechanical characteristics and specific absorbed energy of the filled specimens were superior to those of the unfilled ones. Specimen containing 5% HNT showed maximum energy absorption and mechanical strength. Although the HNT additive has a positive effect on the mechanical and energy absorption in general, it has been determined that the HNT additive affects the performances negatively from 10%.
Effect of Sic and Graphene Nanoparticles on the Mechanical Properties of Carbon Fiber-Reinforced Epoxy Composites
(Wiley, 2023) Kosedag, Ertan; Ekici, Recep; Yildiz, Nail; Caliskan, Umut
This study experimentally investigates the mechanical properties of carbon fiber reinforced epoxy composites (CFRECs) filled with Graphene (Gr) and Silicon Carbide (SiC) nanoparticles. Gr and SiC nanoparticle filled CFREC plates at 0%, 0.5%, 1%, and 2% weight ratios were fabricated using a vacuum infusion technique from unidirectional carbon fiber fabric with both 0 and 90 & DEG; fiber orientation. According to ASTM standards, tensile, compression, and three point bending tests were performed to determine the effects of additive type and weight ratios. CFRECs with Gr additive exhibit improved tensile properties compared to the unfilled composites, especially at higher filler contents and at specific fiber orientations. Also, the Gr additive showed a better improvement in the tensile behavior of the CFRECs than the SiC additive. In general, it was found that the elastic modulus values of nanoparticle additive samples were higher than that of the unfilled composite material in both fiber orientations. Except for the 0.5% SiC ratio with 0 & DEG; fiber orientation, the particle added nanocomposites did not exceed the value of the unfilled composite and did not make a positive effect on the compressive strength. It has been observed that Gr additives give more positive results on the bending strength of CFRECs than SiC, especially at a 2% weight ratio. Highlights center dot Effects of nanoparticle types on mechanical properties of CFRECs were compared. center dot Weight ratio effects on the properties of nanoparticle-filled CFRECs were studied. center dot The load-bearing capacity decreased as the additive ratio increased. center dot Additives and ratios should be carefully selected for the intended applications. center dot Overall, presence Gr resulted in enhanced properties much prominently for composites.
Effect of Stacking Sequence and Metal Volume Fraction on the Ballistic Impact Behaviors of Arall Fiber-Metal Laminates: an Experimental Study
(Wiley, 2022) Kosedag, Ertan; Aydin, Murat; Ekici, Recep
Thanks to their superior mechanical properties, polymer matrix composites have gained considerable importance. In order to improve the impact resistance of polymer matrix composite materials, a new hybrid material known as fiber metal laminate (FML) has been developed. The aim of this study was to reveal the effect of stacking sequence (SS), metal volume fraction (MVF), and number of layers on ballistic resistance in fiber metal laminates (FMLs). Four types of FMLs in different sequences and MVF (25% and 50%) were produced with hot press and vacuum. Ballistic tests were carried out with a single stage gas gun system. The absorbed energy was calculated from the energy difference that occurred by taking into account the FMLs entry and exit velocity of the projectile and the projectile mass. Damage types were examined after ballistic testing. It was determined that the stacking sequence and MVF significantly affect the impact resistance of FMLs. It was determined that the metal layer, which first encounters the projectile, compared to the polymer matrix composite, is more effective on the impact resistance of FMLs, and the impact resistance increased with the increase of MVF. In addition, the increase in the number of layers, if the top layers remain the same, adversely affected the impact resistance. It was observed that the first layer that encounters the projectile and the amount of MVF have a significant effect on the ballistic impact strength. As the amount of MVF increases, the ballistic impact resistance increases.
Free Vibration Analysis of Foam-Core Sandwich Structures
(Gazi Univ, 2021) Kosedag, Ertan; Ekici, Recep
In this paper, the free vibration analyses of aluminum-foam sandwich structures were completed numerically. Foam and aluminum (Al) were used for the core and surface layers of the sandwich structure, respectively. In addition, an adhesive was used as a thin film. Natural frequencies and mode shapes of the sandwich structure were obtained for different thickness core and surface materials. For this, three different sandwich structures, different thickness of the core with same surface layers and the same core thickness with different surface layers thickness, were modeled as SS1, SS2 and SS3. Analyses were performed by ABAQUS/Standard finite element software. The increase in the thickness of the Al layer generally caused a decrease in the frequency, but this decrease is not very dramatic. The increase in the thickness of the core has caused a serious increase in the frequency of the sandwich structure.
Hybridization Effect on Energy Absorption Capacity of Composite Crash Boxes
(Wiley, 2024) Erkek, Baran; Kosedag, Ertan; Adin, Hamit
Crash boxes are safety elements generally made of metallic materials and mounted on the chassis of vehicles to prevent possible injuries to driver and passengers by absorbing the energy generated during a collision and ensuring integrity of vehicle. In order to save fuel and reduce harmful gases released into the environment, the proportion of metallic materials used in vehicles is decreasing and being replaced by composite materials. While composite materials are as durable as metallic materials, they are preferred because they are lighter. In this study, circular composites consisting of glass (S1), aramid (S2), carbon (S3), and hybrid combinations of aramid-carbon-glass (S4), carbon-glass-aramid (S5), and glass-aramid-carbon (S6), all with epoxy resin matrices, were produced using the vacuum infusion method and investigated. Crush parameters, maximum peak loads and specific energy absorption of hybrid tubes with different fiber types and winding order were compared. S3 tube had the best energy absorption performance among all samples of 257.288 Joules, while the worst energy absorption performance was obtained for S2 tube with 30.944 Joules. Among the hybrid samples, the best result was determined as 166.50 Joule with hybrid S5. Although the energy absorption capacities of hybrid composite tubes were close to each other, they had lower results for energy absorption and specific energy absorption than S1 and S3. For specific energy absorption, as with energy absorption, the best result was obtained with S3, while the lowest result was obtained with S2.Highlights The aim of this study is to evaluate the performance of composite crash boxes. The effect of fiber type and hybridization was examined. Specific energy absorptions and maximum contact forces were compared. Cylindrical samples were produced by vacuum infusion. The variation of damage depending on fiber type was investigated. Production and post-test images of hybrid crash boxes. image
The Impact of Graphene Filler on the Energy Absorption of Hybrid Composite Crash Boxes
(Springer Heidelberg, 2024) Erkek, Baran; Kosedag, Ertan; Adin, Hamit
One of the safety components found in vehicles is crash boxes mounted on vehicle chassis. These boxes, when mounted on the vehicle chassis, are intended to preserve the integrity of vehicle and ensure safety of passengers inside during crashs. Since these crash boxes are generally made of metal, efforts are made to reduce the additional weight on vehicles. Therefore, like many other parts in vehicles, there is a tendency to move towards the use of composite materials in crash boxes. In our study, crash boxes with hybridization achieved by altering the winding sequences of glass, aramid, and carbon fibers, with addition of graphene, were experimentally compared in terms of maximum peak forces, energy absorption, and specific energy absorption. Samples were produced with 0.25% graphene addition, with glass fiber G0.25 g, aramid fiber A0.25 g, and carbon fiber C0.25 g, and in hybridization, winding sequences were internally aramid-carbon-glass ACG0.25 g, carbon-glass-aramid CGA0.25 g, and glass-aramid-carbon GAC0.25 g. Similarly, samples labeled G0.50 g-GAC0.50 g were produced with 0.50% graphene addition. As a result, the best maximum peak force and specific energy absorption were achieved with the 0.50% graphene-added C0.50 g, at 8.52 kN and 10.08 J/g respectively. While the best energy absorption was with C0.25 g at 228.25 J, the worst was with glass fiber G0.25 g at 21.78 J. The addition of graphene to A0.25 g and A0.50 g, namely the aramid fiber samples, significantly increased their values by forming a good structure.
Investigation of Cell Size Influence on the Crushing Behavior of Gyroid Lattices Fabricated Via Fdm
(Taylor & Francis inc, 2025) Kosedag, Ertan
This study investigates the influence of cell size on the mechanical performance and damage mechanisms of gyroid structures fabricated via Fused Deposition Modeling (FDM) using PLA. Gyroid structures, a type of triply periodic minimal surface (TPMS), are recognized for their excellent energy absorption and lightweight characteristics, making them promising for various engineering applications. Four sets of gyroid structures with cell sizes of 5, 10, 20, and 30 mm were produced and subjected to quasi-static compression tests to evaluate their force-displacement behavior, total energy absorption, and specific energy absorption. The experimental results revealed that structures with smaller cell sizes (5 and 10 mm) exhibited more uniform deformation and controlled collapse, resulting in higher energy absorption and more efficient stress distribution. In contrast, larger cell sizes (20 and 30 mm) demonstrated a significant decline in both total and specific energy absorption. Moreover, the damage analysis indicated that as the cell size increased, failure patterns became increasingly irregular, with a higher fracture ratio observed in larger cell structures. These findings suggest that cell size plays a crucial role in determining the overall performance and reliability of gyroid TPMS structures under quasi-static loading conditions. The insights from this study provide valuable guidelines for the design and optimization of TPMS based components, especially in applications where energy absorption and impact resistance are critical.
Kesit Geometrisinin ve Malzeme Tipinin Çarpışma Kutularının Enerji Emme Yeteneklerine Etkisi
(2023) Kosedag, Ertan; İşler, Devrim
Bu çalışmada, otomotiv sektöründe kullanılan ve meydana gelen bir kaza sırasında enerji absorpsiyonunu sağlayan çarpışma kutularının enerji absorpsiyon yetenekleri araştırılmıştır. Bu amaçla Al6063 ve A36 çelik olmak üzere iki farklı malzeme ve dört farklı geometride çarpışma kutuları tasarlanmıştır. Üçgen, kare, dairesel ve altıgen kesit geometrilerinin ve malzeme tipinin enerji absorpsiyonuna etkileri, kesit alanları aynı kalmak şartıyla sonlu elemanlar yöntemi kullanılarak incelenmiştir. Sonlu elemanlar yöntemi ile yapılan analiz sonuçlarında mesh boyutunun etkisini en aza indirmek için meshten bağımsızlaştırma ön çalışması yapılmıştır. Daha sonra farklı geometrik kesitlerden ve farklı malzemelerden oluşan çarpma kutuları aynı sınır şartlarında çarpışma testlerine tabi tutulmuştur. Analizler sonucunda, çarpışma kutuları tarafından emilen enerjil miktarları, hasar modelleri, kuvvet-zaman eğrileri elde edilmiştir. Bu sonuçlara göre en çok enerji yutan geometriden en az enerji yutan geometriye doğru sıralama altıgen, daire, kare ve üçgen şeklindedir. Her iki malzeme türü için de benzer sonuçlar elde edilmiştir. Çelik malzemenin, alüminyum malzemeden yaklaşık on kat daha fazla reaksiyon kuvveti gösterdiği tespit edilmiştir.
Low-Velocity and Ballistic Impact Resistances of Particle Reinforced Metal-Matrix Composites: an Experimental Study
(Sage Publications Ltd, 2022) Kosedag, Ertan; Ekici, Recep
This study investigates the low-velocity and ballistic impact responses of SiC-reinforced Al6061 metal-matrix composites in different reinforcement volume fractions. Low-velocity impact (LVI) tests were performed with samples having SiC particle volume fractions of 0, 5, 10, 15, 20, 30, and 40%, while ballistic tests were carried out with samples having volume fractions of 0, 10, 20, and 30%. The weight-drop test method was used for LVI by applying 50 J (4.45 m/s) energy to all samples. Ballistic tests were carried out under the same conditions on all samples with the projectile launched at an average velocity of 500 m/s. For the determination of the ballistic resistance of the samples, the projectile penetrations in the witness structures were taken into consideration. The damage and deformations caused by both the LVI and the ballistic test in composites were examined. By the LVI test results, composite samples have absorbed less impact energy by increasing the reinforcement volume fraction, as well as demonstrated superior performance compared to unreinforced samples. In addition, the crack formation was mainly observed in the samples containing 30% reinforcement, while the composite material with a 40% volume fraction was completely broken. With the increase in the reinforcement volume fraction, the ballistic resistance of the samples increased significantly.
Low-Velocity Impact Behaviors of B4c/Sic Hybrid Ceramic Reinforced Al6061 Based Composites: an Experimental and Numerical Study
(Elsevier Science Sa, 2025) Kosedag, Ertan; Ekici, Recep
This study studied the low-velocity impact behavior of silicon carbide (SiC), boron carbide (B4C), and hybrid B4C/SiC reinforced aluminum 6061 alloy (Al 6061) matrix composites experimentally and numerically. The effect of hybridization, reinforcement volume fraction, and reinforcement type on low-velocity impact was investigated. 16 different metal-matrix composite materials were manufactured for the study, including 9 hybrid samples, 6 non-hybrid samples for each reinforcing ceramic particle, and 1 unreinforced sample. The powder metallurgy - hot press method was used in experimental production and then low-velocity impact tests were carried out. Numerical study was carried out using the non-linear finite element method (FEM). A Python algorithm running on ABAQUS/Explicit was utilized to determine ceramic particle distribution based on volume fraction, hybridization ratio, and random particle arrangement. The Johnson-Cook Plasticity Model was used for the non-linear relationship between stress and strain in the Al 6061 metal-matrix during impact. The results were interpreted with the contact force-time, contact force-displacement, and energy-time data obtained from lowvelocity impact tests. In addition, the amount of collapse that occurred during the impact was measured and compared, and finally, SEM/EDX analysis was performed for the microstructure characterizations of the composite sample. Impact tests revealed that the collapse of composite samples ranged from 3.06 mm to 3.58 mm, with the unreinforced S6 sample collapsing 4.18 mm, indicating that increased reinforcement elements reduce ductility, while a lower B4C ratio or higher SiC ratio in hybrid composites leads to greater collapse. Keeping the hybridization rate constant while increasing the reinforcement ratio leads to an increase in contact force and a decrease in contact time. Hybrid composites exhibited higher stiffness as SiC content increased, while B4C reinforced non-hybrid composites showed more significant stiffness. There is good agreement between the numerical and experimental results. Non-hybrid samples have a better match between numerical predictions and experimental results than hybrid samples.
Microstructure and Mechanical Behavior of Pumice Particle Reinforced Magnesium Matrix Composites
(Springer Heidelberg, 2024) Aydogmus, Tarik; Kosedag, Ertan
In the present study, novel, lightweight and low-cost Mg/pumice composite materials have been developed for the first time. Mg matrix composites reinforced with 3-12 vol.% pumice powders were produced by hot pressing at 600 degrees C for 1 h under 50 MPa pressure. Microstructural analysis revealed that in-situ Mg2Si and MgO phases formed as a result of chemical reaction between pure Mg powders and SiO2 present in the pumice powders during processing. The room and elevated temperature (150 degrees C and 200 degrees C) yield and compressive strength of the composites increased with increasing reinforcement content. The increments up to 47.5% in yield strength and 53% in compressive strength at room temperature have been observed. Similarly, the utmost increments in yield and compressive strength at elevated temperatures were 72% and 50.5%, respectively. Ductility (especially at the room temperature) of the composites on the other hand was almost independent of the reinforcement content.
Pomza Dolgulu Epoksi Esaslı Kompozitlerin Dolgu Oranının Mekanik Özelliklerine Etkisinin İncelenmesi
(2023) Kosedag, Ertan
Bu çalışmada yaygın olarak kullanılan ve endüstriyel bir malzeme olan epoksi, ucuz volkanik bir kayaç olan pomza ile doldurularak kompozit bir malzeme elde edilmeye çalışılmıştır. Amaç, pomzayı katma değeri yüksek olarak değerlendirmek ve epoksinin mekanik özelliklerini iyileştirmektir. Dolgusuz, %10, %20 ve %30 dolgulu kompozit numuneler üretilmiştir. Üretim sırasında bir ultrasonik karıştırıcı kullanılarak tozun homojen bir şekilde dağılması sağlanmıl ve vakumlama ile hava ceplerinin kompozitte birikmesi önlenmiştir. Kompozitlerin mekanik özellikleri basma testi ile tespit edilmiş ve tozun üretim sonrası dağılımı optik mikroskop resimleri kullanılarak gözlemlenmiştir. Son olarak, pomza tozunun bileşimini belirlemek için XRF analizi kullanılmıştır. Sonuçlar, dolgu maddesi eklenmesinin kompozitlerin maksimum gerilim ve gerinim değerlerini büyük ölçüde artırdığını göstermiştir. Optimum mekanik değerler %20 pomza dolgulu kompozitte bulunmuştur. %20 dolgulu kompozit malzemenin maksimum gerilme değeri 30,6 MPa ve bu noktadaki eşdeğer birim gerinim mekanik test bulgularına göre %0,049 olarak bulunmuştur.
Repeated Low-Velocity Impact Responses of Sic Particle Reinforced Al Metal-Matrix Composites
(Elsevier Sci Ltd, 2022) Ekici, Recep; Kosedag, Ertan; Demir, Mert
This study aimed to investigate experimentally the repeated low-velocity impact behaviors of SiC reinforced aluminum 6061 metal-matrix composites for different volume fractions and energy levels. In addition, the hardness variations were measured by the Vickers hardness tests from the impacted and impact-free cross-sections of the particle reinforced metal-matrix composites. Low-velocity impact tests were applied to composite samples manufactured by powder metallurgy (in 10, 20, and 30% volume fractions) at two total energy levels (15 and 60 J as single) and in repetitions equal to the sum of these energy levels (5 + 5 + 5 and 20 + 20 + 20 J as repeated). As a result, in increasing the impact number for all volume fractions, the total contact time was shortened and the peak contact force increased, whereas both the permanent central deflection and the absorbed energies reduced. Hence, these variations obtained under repeated impacts (5 + 5 + 5 and 20 + 20 + 20 J) revealed that metal-matrix composites showed a tougher behavior with an increase in the impact numbers from 1st to 3rd, particularly because of the strain hardening effect. Furthermore, an increase in volume fraction from 10 to 30% resulted in an increase in the impact strength under all repeated and single impacts despite changing deformation and damage mechanisms due to increasing the strain hardening effect and particle fractures. The hardness was affected by the volume fraction and increased as the volume fraction increased in both the impacted and impact-free zones. The repeated impact increased the impacted zone hardness more than the single impact for all volume fractions. Additionally, the hardness of the impacted zone under 20 + 20 + 20 J repeated impact was measured as the highest value in the 30% volume fraction. Therefore, metal-matrix composites can behave harder with the strain hardening effect under repeated impacts.
Tetikleyici Tipinin Dairesel Kftp Çarpışma Kutusu Enerji Emilim Performansına Etkisi
(2024) Kosedag, Ertan
Bu çalışmada enerji absorpsiyon performansı üzerine tetikleyici etkisinin incelenmesi için karbon fiber takviyeli polimer matrisli kompozitler üretilmiştir. Üretim vakum infüzyon metodu ile gerçekleştirilmiştir. Üretilen kompozit çarpışma kutularının üzerine üç çeşit tetikleme geometrisi açılmış ve bir de tetikleyici içermeyen karşılaştırma numunesi hazırlanmıştır. Bu dört farklı numunenin yarı-statik basma testleri gerçekleştirilmiş ve elde edilen datalar ile numunelerin enerji emme performansları değerlendirilmiştir. Bunun yanında numunelerin hasarları incelenmiş ve tetikleyici ile nasıl değiştiği ortaya konmuştur. Buna göre S-2 olarak tanımlanan numune (üst yüzeyinden aşağıya doğru dört simetrik yarık ile tetiklenen numune), emilen enerji açısından en iyi performansı sergilemiştir. Ayrıca açılan tetikleyiciler ile tepe kuvveti düşürülmüş ve maksimum tepe kuvveti azalmaları S-3 (delik tipi tetikleyiciye sahip) ve S-4 (yatay yarık tipi tetikleyiciye sahip) numunelerinde görülmüştür.