Yılmaz, Çağatay
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Yilmaz, Cagatay Çağatay Yılmaz
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Dr. Öğr. Üyesi
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yilmaz.cagatay@agu.edu.tr
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02.06. Makine Mühendisliği
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14 results
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Article ASTM-D638 Numune Tipinin Erimiş Biriktirme Modelleme 3D Baskılı PLA Numunelerinin Çekme Özelliklerine Etkisi(2025) Yilmaz, Cagatay; Eltahir, Sara Saeed Abdulrahman; Gomaa, RoaaBu araştırma, farklı ASTM-D638 numune türlerinin 3D baskılı PLA malzemelerinin mekanik özelliklerini nasıl etkilediğini incelemektedir. Numune türleri, ASTM-D638 standartlarında tanımlandığı gibi, beş farklı türü içeren, mekanik testlerde kullanılan test numunelerinin belirli konfigürasyonlarını ifade eder: Tip I – Tip V. Bu standart, tutarlı ve karşılaştırılabilir test prosedürlerini sağlamak için çeşitli numune geometrilerini ve boyutlarını özetlemektedir. Polilaktik asit (PLA) ile ilgili çalışmalar. Bilgisayar destekli tasarım (CAD) modelleri oluşturulur ve PLA numuneleri üretmek için Erimiş Biriktirme Modelleme (FDM) 3D baskı kullanılır. Numunelerin mukavemetini ve gerinimini ölçmek için sırasıyla çekme testi ve Dijital Görüntü Korelasyonu (DIC) analizi yapılır. Çalışma, numune türünün parça özellikleri üzerindeki etkisine ilişkin kapsamlı veriler sağlamayı ve DIC ve akıllı telefon kullanılarak uygun maliyetli bir gerinim ölçüm yöntemi göstermeyi amaçlıyor. Metodoloji, CAD modellemeyi, 3D yazdırmayı, yüzey hazırlığını, çekme testini, Ncorr kullanılarak DIC analizini ve MATLAB veri işlemeyi içerir. Sonuçlar, Tip I ve Tip II'nin sırasıyla 43,179 MPa ve 43,164 MPa ile en yüksek nihai gerilme mukavemetini (UTS) sergilediği gerilim-gerinim eğrilerini ve ortalama gerinim değerlerini gösterir. Ancak Tip V, kısa baskı süresi ve Tip I'e göre 5 kat daha az olan düşük filament kullanımı ve 42.640 MPa'lık makul UTS'si nedeniyle en optimum seçenektir. Bu araştırma, numune tasarımının 3D baskılı parça özellikleri üzerindeki etkisine ilişkin bilgi boşluğunu doldurarak gelecekteki araştırmalar için değerli bilgiler sağlıyor.Article Citation - WoS: 12Citation - Scopus: 14The Effect of Different Tabbing Methods on the Damage Progression and Failure of Carbon Fiber Reinforced Composite Material Under Tensile Loading(Elsevier Sci Ltd, 2022-07) Ali, Hafiz Qasim; Yilmaz, Cagatay; Yildiz, MehmetComposites are well-known and widely used materials due to their anisotropic nature and high strength-to-weight ratio; therefore, the mechanical performance of these materials is crucial. Precise tensile testing is essential to obtain material properties that are crucial for the design stage of composite structures. This study is an effort to investigate the effect of adhesive materials used for tabbing process, which is necessary for the tensile testing procedure. Araldite and AF 163-2k film are used as the adhesive film, whereas in the case of AF 163-2k, tabbing is done through two different procedures (Jig and corner holes method). Apart from the tensile per-formance, strain distribution and damage progression are monitored simultaneously using digital image corre-lation (DIC) and acoustic emission (AE) analysis. It is observed that there is no significant difference in the ultimate tensile strength of these composites tabbed with different adhesives and procedures. Nevertheless, the first major failure strength is much higher in Araldite tabbed specimens compared to AF 163-2k film (the first major failure activity is defined as a point at which material loses its integrity, especially when considering structural or aerospace applications). Also, strain distribution throughout the gauge length recorded via DIC is appreciably different, which is attributed to damage accumulation and progression monitored by AE analysis. The frequency-based analysis of AE data is performed to classify the damage, and cumulative energy is correlated with the DIC to navigate the failure activity at different times and stress levels.Article Performance Evaluation of Energy Companies With a Novel Integrated Multi- Criteria Decision Making Method(Kafkas University Iibf, 2022-12-27) Madenoglu, Fatma Selen; Unlusoy, Omer Faruk; Yilmaz, CagatayFinancial statements are an important tool for assessing and analyzing an organization's financial performance. Financial performance analysis allows for an accurate and appropriate appraisal of an organization's performance. The evaluation procedure must be thoroughly stated because financial performance indicators represent a company's competitiveness. This study provides a novel integrated multi-criteria decision-making method for analyzing an organization's financial performance. The applicability of the proposed method is assessed employing financial ratios that are integrated to generate a financial performance score for eight well-known Turkish energy companies. The criteria are weighted using the entropy method in the proposed method. The multi- attributive border approximation area comparison (MABAC) method is used to rank the companies. As the weights of the criteria have an impact on the ranking outcomes, a sensitivity analysis of the weights is performed. We also exhibit a comparison analysis of energy company rankings to validate the proposed approach's results using four MCDM methods: ELECTRE, MAUT, TOPSIS, and WASPAS. In addition, an alternative weighting method is also used to evaluate the results. The results show that the proposed method is an effective MCDM for coping with evaluation problems.Article Citation - WoS: 11Citation - Scopus: 11Monitoring and Verification of Micro-Strain Generated Inside the Laminate Subjected to Thermal Loading Through Fiber Bragg Grating Sensors and Classical Laminate Theory(Wiley, 2023-03-23) Yilmaz, Cagatay; Ali, Hafiz Qasim; Yildiz, MehmetFiber Bragg Grating (FBG) sensors possess enormous potential for the cure monitoring and integrity assessment of Carbon Fiber Reinforced Polymer (CFRP) composites. These sensors can be embedded inside the structure to monitor the strain in the desired region of interest. The strain on an FBG sensor can be calculated by measuring the change in the center wavelength of the sensor. This change in center wavelength is a function of temperature and mechanical strain. Therefore, temperature compensation is necessary for a precise mechanical strain measurement with an FBG sensor. In this study, FBG sensors are embedded in different layers of the CFRP laminate to record the mechanical strain caused by the thermal expansion, which happens under the influence of temperature. Classical laminate theory (CLT) is implemented to assess the accuracy of FBG sensor measurements and the strain data acquired from both FBG sensor and CLT correlates. Furthermore, a resistive strain gauge is deployed to measure the strain under the influence of temperature. It is depicted that strain values recorded by the strain gauge under the influence of the temperature do not agree with the strain measured by CLT, and an error of 150% occurs among their values.Article A Parametric Study for Drilling High Quality Holes on Glass Fiber Composites(2022) Yilmaz, Cagatay; Kesriklioglu, SinanThe objective of this study is to investigate the effect of cutting parameters on the qual- ity of holes drilled in a glass fiber reinforced thermoset polymer with the delamination factor defined as the ratio of intended hole diameter to the diameter of the maximum area which contains both hole and delaminated area. For this purpose, Taguchi's L9 or- thogonal array was used to design the experiments and optimize the drilling parameters. 5 mm twist drill bits were used to drill the holes at various feeds and spindle speeds. The maximum diameters on the inlet and outlet sides of the holes drilled into the composite plates were then measured with an optical microscope to analyze the influence of the drilling parameters on the machining damage. The smallest delaminated area on the front and back sides of the composite plate was achieved with the lowest feed (0.05 mm/rev) for the drilling parameters used in this study. Even though the spindle speed was increased from 318 rpm to 2930 rpm at a constant feed of 0.05 mm/rev, it reduces the maximum diameter on the front and back sides by 9 μm and 266 μm, respectively. The obtained results showed that the material removal rates in the drilling of the glass fiber reinforced thermoset polymers can be increased significantly by setting the optimized process pa- rameters without adversely affecting the hole quality.Article Experimental Comparative Analysis of Hole-Making Strategies and Cutting Parameters on Flexural Properties and Induced Delamination in S2 Glass and Basalt Fiber-Reinforced Polymers(John Wiley and Sons Inc, 2026) Eltahir, Sara Saeed Abdulrahman; Yilmaz, Cagatay; Kesriklioglu, SinanOpen holes are often required in the applications of fiber-reinforced polymers (FRP). However, machining them leads to fiber and matrix damage, reducing the overall quality of composites. The novelty of this study lies in investigating the influence of multiple hole machining strategies under varying feed rates and cutting speeds on the flexural strength, chord modulus and hole quality for S2-Glass (S2-GFRP) and basalt fiber-reinforced polymers (BFRP), followed by three-point bending tests and statistical analysis to determine the optimum machining parameters in terms of flexural properties, delamination, and time efficiency. Findings indicate that conventional milling yields an increase in the flexural strength and chord modulus by 22.2 MPa and 1.9 GPa, respectively, for S2 GFRP. While climb milling performs best for BFRP, enhancing flexural performance by 7.6 MPa and 0.4 GPa. Direct drilling at high feed rate and cutting speed shows the poorest performance. Hole machining at low feed rate using climb milling minimizes delamination at the entrance by 14.8% for S2 GFRP and by 2.7% for BFRP using conventional milling. At the exit, helical milling at a low feed rate suppresses delamination damage by 58.5% and 10.7% for S2 GFRP and BFRP. The most time-efficient method is direct drilling at a feed rate of 0.075 mm/rev and cutting speed of 75 m/min or climb milling with same feed rate, but 25 m/min cutting speed. Within the tested ranges, the optimized drilling setup significantly improved structural performance of S2-GFRP and GFRP, confirming the effectiveness of the proposed experimental-statistical framework.Article Surface Integrity and Tool Wear in S2-GFRP Milling: Experimental and Statistical Evaluation of Cutting Parameters and DLC and TiAlN Tool Coatings(Springer London Ltd, 2026) Danisman, Sengul; Yilmaz, Cagatay; Ersoy, Emin; Kesriklioglu, SinanIn this study, the surface integrity of S2-glass fiber-reinforced polymer (S2-GFRP) composites during milling with carbide cutters was investigated using a two-phase experimental design, focusing on surface roughness (Ra), burr area, and tool wear (VB). In the first phase, using a Taguchi L9 design, the effects of coating type (uncoated, TiAlN, DLC), spindle speed (2000-6000 rpm), and feed rate (0,15-0,25 mm/rev) on Ra and burr area were evaluated. In this short machining range where tool wear was negligible, the optimal combination yielding the lowest Ra (approximate to 0.97 mu m) and the minimum burr area (approximate to 231 mm & sup2;) was determined to be 4000 rpm, 0,15 mm/rev, and the DLC-coated tool. Regarding the effect of tool material on Ra, the DLC-coated tool provided approximately 4 and 2 times better results than the uncoated and TiAlN-coated tools, respectively. In the second phase, experiments extended up to 130 passes with this optimal parameter set showed that Ra increased significantly with increasing VB, and the burr area exhibited threshold-like behavior. In particular, a sudden increase in Ra and the burr area was observed when the VB approximate to threshold of approximately 100 mu m was exceeded; partial regression analyses confirmed different burr-formation tendencies in the low- and high-wear regimes. The results reveal that DLC coating initially provides superior performance in S2-GFRP milling, but surface degradation accelerates after the critical VB threshold.Article Application of Hooke’s Law to Angle Ply Lamina(2022-12-29) Yilmaz, Cagatay; Ali, Hafiz Qasim; Yildiz, MehmetAerospace-grade carbon fiber reinforced polymer composite plates with four different fiber orientations 0º, 30º, 45ºand 60º is produced with the autoclave curing method and subjected to tensile testing. The stress-strain curves of the composite specimens are compared with Hooke’s law. It is observed that Hooke’s law coincides precisely with the experimental results for samples containing fibers parallel to the loading direction. However, it does not coincide with samples where the fibers make a certain angle with the applied load direction.. Moreover, it is reported that Hooke’s law converges the experimental results for small strain values but diverges significantly from the experimental results at higher strain values.Article Citation - WoS: 22Citation - Scopus: 27Basalt Fiber Reinforced Polymers: A Recent Approach to Electromagnetic Interference (EMI) Shielding(Wiley, 2024-10-09) Fareez, Umar Naseef Mohamed; Loudiy, Aymen; Erkartal, Mustafa; Yilmaz, CagatayElectromagnetic wave (EMW) radiation pollution is getting more severe as result of the advancement of electronic technology. Researching shielding materials with superior EMI (electromagnetic interference) shielding characteristics is therefore crucial. Basalt fibers (BFs) have been an emerging candidate in the fiber-reinforced polymer (FRP) category due to their favorable mechanical and chemical properties, along with being favorites in sustainability and having low production costs. Therefore, due to the rising need for cheaper and efficient alternatives in the EMI shielding industry, the EMI shielding is covered in terms of BF composite materials and their properties in this review, starting with the EMI shielding mechanism and followed by how BF composites affect the EMI properties. This review then covers the post-treatments of BF composites and, finally, the factors of the composites that affect the EMI properties. Moreover, the EMI shielding applications in which BFRPs are used are comprehensively discussed as well. This review aspires to bridge an understanding between EMI shielding as a material property and the BF composites that are developed to aid in the EMI shielding application.Article Application of Classical Lamination Theory to Fused Deposition Method 3-D Printed Plastics and Full Field Surface Strain Mapping(2022-04-30) Yilmaz, Cagatay; Ali, Hafiz Qasim; Yildiz, MehmetBu çalışmada üç boyutlu yazıcı ile Eriyik Yığma Modellemesi (EYM) yöntemi kullanılarak farklı yazma yönlerindeki katmanlara sahip toplamda beş set çekme örneği üretilmiştir. Üretilen üç farklı sete çekme testi yapılarak farklı yönlerdeki elastik sabitler daha sonra Klasik Laminasyon Teorisinde (KLT) kullanılmak üzere ölçülmüştür. Klasik Laminasyon Teorisi genel olarak tek yönlü fiberler ihtiva eden polimerik yapıların modellenmesi için kullanılmaktadır. Bu çalışma ile KLT üç boyutlu yazıcı ile üretilen ve içerisinde herhangi bir fiber takviyesi ihtiva etmeyen ve her katmanda yazma yönleri değişen iki farklı polimerik yapıya uygulanmıştır.KLT ile elde edilen gerinim ve gerilme değerleri çekme deneyi ile elde edilen gerinim ve gerilme değerleri ile karşılaştırmıştır. Elde edilen sonuçlara göre düşük gerinim değerleri için KLT ile elde edilen sonuçların deneysel sonuçlar ile uyumlu olduğu, yalnız gerinim değeri arttıkça KLT ile hesaplanan değerlerinin deneysel değerlerden uzaklaştığı görülmüştür.Daha sonra ise Eriyik Yığma Modelleme Yöntemi ile üretilen üç boyutlu plastiklerin hasar ilerlemesi ve kırılması Dijital Görüntü Korelasyon Tekniği ile Tam Alanlı Yüzey Gerinim Haritalanması kullanılarak çıkarılmıştır.