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• MakaleYalnız künye2026Scopus SJRQ2/r/bayburt/12819
  Comparative investigation of composite-metal lap joints with mono-adhesive and thermoplastic-reinforced mixed adhesive at elevated temperatures

  Erbayrak, Engin; Eker, Beril; Colak, Murat

  This study primarily examines the strength of a single lap joint having a mixed adhesive overlap consisting of a single adhesive and its thermoplastic reinforced state under varying temperatures. In the single lap joint, Titanium-Boron reinforced A356 aluminum was employed as the metal adherend, while plain woven glass fiber-reinforced epoxy (GFRE) was employed as the composite adherend. In the application of the mixed adhesive overlap, the brittle adhesives were employed in the middle section of the lap joint, while the reinforcement of the thermoplastics was employed on the adhesives at both sides of the lap joint. The single lap joints were subjected to tensile tests at 1 mm/min loading rates under room temperature and 120 °C, which is the melting point of the copolyester. In the numerical analysis, the cohesive zone model was applied in order to define the adhesives; however, elastic isotropic and orthotropic material behaviors were employed for the metal and composite adherends, respectively. Eventually, it is determined that the strength of a mixed adhesive lap joint consisting of a single adhesive and its thermoplastic reinforced state is better than a lap joint made with the mono-adhesive alone. Although literature suggests that mixed adhesive overlaps can be formed using at least two different adhesives (one ductile and one brittle), this study demonstrated that a mixed adhesive zone can be created using a single adhesive and thermoplastic reinforcement.

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• MakaleAçık Erişim2026Scopus SJRQ2/r/bayburt/11576
  Low-velocity impact analysis of metal-composite joints with grain-refined A356 and reinforced epoxy adhesive using six node pentahedron cohesive elements

  Erbayrak, Engin; Colak, Murat; Noberi, Cansu

  This study evaluates the strength of double lap joints composed of metal composite adherends and epoxy adhesive subjected to low impact energies (20 J, 40 J). The study was carried out through experimental and numerical methods to understand the strength of lap joints comprehensively. In the production of double lap joints, A356 aluminum and grain-refined aluminum adherends were used as the metal components. To refine the grain structure, titanium (Ti) and boron (B) were added to the liquid metal at a rate of 0.01% of the total metal weight (A356-TiB). The composite laminates consisted of glass/epoxy and aramid/epoxy, made with unidirectionally oriented fibers. Araldite 2015 epoxy adhesive, available in both unreinforced and copolyester-reinforced forms, was utilized to bond the metal and composite materials. In the numerical analysis of double-lap joints, the metal and composite adherends are modeled using 8-node solid elements, while the adhesive is represented by 6-node pentahedron cohesive elements. Furthermore, a surface-to-surface, two-way treatment of contact was created between the impactor and the metal adherend. Consequently, the maximum impact loads obtained from the numerical analysis are in good agreement with the experimental results for both impact energies.

  AtıfScopus4·WoS5·OpenAlex4

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• MakaleAçık Erişim2026Scopus SJRQ2/r/bayburt/11432
  Investigation of the Effect of Niobium Addition on Fluidity and Mechanical Properties in Casting of Aluminum Alloys

  Çolak, Murat; Yalçin, Önder

  Aluminum and its alloys are important engineering materials widely used in the defense industry, industrial production, and machinery industry. Depending on the increase in quality expectations from aluminum casting alloys, castings are made with different alloy element additions. In the study, the effects of Nb addition to A356 aluminum alloy on casting properties were investigated with experimental studies. The Nb addition rate in the alloy was determined as 0.03%, 0.06% and 0.1%. Four-channel fluidity mold with varying section thicknesses, spiral fluidity mold and mechanical test mold were used in casting experiments. As a result, with the addition of Niobium, an increase in maximum tensile strength and % elongation was observed, while a decrease in fluidity properties was observed.

  AtıfScopus4·WoS5·OpenAlex4

  İncele
• MakaleAçık Erişim2026Scopus SJRQ2/r/bayburt/11272
  Relationship Between Aluminum Liquid Metal Quality and Defects

  Kutsal, Umit; Colak, Murat; Ertugrul, Onur

  Aluminum alloys are commonly used in various industries today. In order to produce defect-free high-quality alloys with sustainable processes, defects must be reduced, and liquid metal quality must be improved. There are various methods that can be used for the measurement of liquid metal quality. Some of which are density index, bifilm index, K-Mold index, PoDFA, Prefil, fluidity test, and thermal analysis. The relationship and validation between these methods are still not clear. In this study, the relationship between aluminum liquid metal quality and defects is analyzed. Three different conditions were utilized. These conditions are (1) before a controlled degassing, (2) after the controlled degassing and (3) after the liquid metal is transferred to the holding furnace. According to the results, it was observed that the reduction of bifilms index did not reduce other inclusions and did not always favorably affect other measurement methods. It was also observed that the reduction of bifilm index did not improve the porosity level. Moreover, it was found that elongation values are related to the largest defect diameters. Bifilm index are not the only factor affecting the elongation and the density index directly affects the defect distribution. K-Mold index has an impact as it shows macro-inclusions. However, bifilm index, density index, fluidity index and K-Mold index are not as sufficient as numerical calculation of defect size by computed tomography (CT). The main factor directly affecting the elongation and tensile strength was found to be the inclusion size and diameter in the CT result. Examination of the fracture surfaces revealed that oxide contents are present, and the oxygen orientations and aluminum orientations are compatible. This harmony is thought to be related to the orientation of the bifilms in the structure.

  AtıfScopus8·WoS8

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• MakaleYalnız künye2026Scopus SJRQ2/r/bayburt/11231
  Identifying the optimal flexural performance of metal-composite single-lap joints with copolyester-reinforced epoxy adhesive under various loading rates using the Grey Relation Analysis

  Erbayrak, Engin; Erbayrak, Seda; Eker, Beril; Colak, Murat

  This study examines the best flexural performance of metal composite single-lap joints fabricated with copolyester-reinforced epoxy adhesives at various loading rates using the Grey Relation Analysis (GRA). The study consists of three parts. The first part involves the formation of metal composite single-lap joints and their experimental approach under different loading rates. In the experimental approach, A356 aluminum was used as the metal material with the addition of titanium (Ti) and boron (B) additives. Plain-woven glass fiber-reinforced epoxy (GFRE) and plain-woven carbon fiber-reinforced epoxy (CFRE) were served as the composite materials. The lap joints were tested in three-point bending tests under loading rates of 1, 10, and 50 mm/min, respectively. In the second part, a numerical analysis was conducted using boundary conditions similar to the experimental conditions. In the numerical analysis, a 6-node pentahedral cohesive element was utilized, representing a novel approach for modeling adhesives in finite element analysis (FEA). When experimental and numerical results were compared, a difference of 4.36% was observed between the maximum load values and 6.80% between the failure displacements. Based on these results, it can be said that the experimental results converge with the numerical results. In the last part of the study, performance rankings of metal composite joints were determined using the Grey Relational Analysis (GRA) method, which enabled us to identify the optimum joint. This systematic approach facilitated the scientific design of joints that demonstrate optimal flexural performance under various loading conditions.

  İncele
• MakaleYayıncıda açık erişim2026Scopus SJRQ3/r/bayburt/11173
  Investigation of Fe and Mn Effects on the Fluidity Behavior of A356 Aluminum Alloys

  Çolak, M.; Alkan, N.; Kutsal, Ü.

  The fluidity behavior of Al–Si casting alloys is strongly influenced by impurity elements and intermetallic phase formation during solidification. In particular, iron (Fe) reduces melt fluidity by forming brittle Fe-rich intermetallics, whereas manganese (Mn) can mitigate this effect by modifying intermetallic morphology. In this study, secondary A356 aluminum alloys were produced with Fe contents of 0.10, 0.15, and 0.20 wt.% and nominal Mn additions of 0.05, 0.10, and 0.20 wt.% to investigate their combined effect on fluidity behavior. Melt quality was assessed using reduced pressure testing and density index measurements to ensure consistent casting conditions. Fluidity tests were conducted using spiral and eight-channel molds with section thicknesses ranging from 0.5 to 8 mm. To enable quantitative comparison across different section geometries, a Fluidity Index (FI) was defined based on section-normalized flow lengths. The results show that increasing Fe content generally reduces fluidity, while Mn additions significantly improve melt flow, with the most pronounced enhancement observed at 0.20 wt.% Mn. Thinner sections were found to be more sensitive to Fe-related flow restriction, whereas wider channels exhibited improved flow behavior. These findings demonstrate that appropriate Mn additions can effectively stabilize fluidity in secondary A356 alloys and provide practical guidelines for alloy control in recycled aluminum casting applications.

  İncele
• MakaleAçık Erişim2026Scopus SJRQ3/r/bayburt/11135
  Optimization of Rotary Degassing Parameters to Improve Melt Cleanliness and Mechanical Properties in A356 Aluminum Alloy

  Kutsal, U.; Çolak, M.; Sağnak, Y.; Bardakci, S.; Ammas, G.; Sarper, G.

  Melt cleanliness is a critical factor that directly affects the quality of aluminum castings and becomes even more significant in recycling-oriented production, where high scrap utilization is inevitable. Increasing the proportion of scrap intensifies the risk of oxide films, inclusions, and gas porosity in the molten metal; therefore, efficient refining techniques are essential. In this study, the effects of rotary degassing parameters—including rotor speed, rotation time, and gas flow rate—on melt cleanliness of A356 aluminum alloy were systematically investigated. Experimental melts containing 20% primary and 80% scrap aluminum were treated under various degassing conditions using a commercial flux cleaning flux. Characterization was performed through the Reduced Pressure Test (RPT), bifilm index analysis, fluidity measurements, microstructural examinations, and mechanical testing (tensile test and Brinell hardness measurement). The results demonstrated that increasing the rotor speed from 200 rpm to 500 rpm significantly reduced both the density and bifilm indices, indicating a notable improvement in melt cleanliness. Furthermore, higher gas flow rate (10 L/min) and longer rotation time (10 min) provided additional but secondary improvements. Consequently, the optimization of rotary degassing parameters enhanced not only melt quality but also tensile strength and ductility. These findings offer practical insights for optimizing process control in recycling-based aluminum foundries.

  İncele
• MakaleAçık Erişim2026Scopus SJRQ2/r/bayburt/11094
  Bioinspired Sternal Implant Design for Generic Anatomical Reconstruction: An In Silico Framework for Material Selection and Biomechanical Validation

  Kutbay, Işıl; Gerdan, Zeynep; Çolak, Murat; Tabak, Yasemin; Şensoy, Abdullah Tahir

  The sternum protects the intrathoracic organs and contributes to chest wall mechanics, which makes reconstruction after tumor resection, trauma, or infection a demanding biomechanical problem. This study presents an in silico workflow for preselecting materials for sternal implants before physical prototyping. After a virtual resection, an anatomically conformal implant was designed and candidate biomaterials were screened in CES Selector using density, elastic modulus, fatigue strength, fracture toughness, toxicity, medical grade suitability, and MRI safety. A representative subset of the screened candidates was then compared by finite element modeling in terms of stress transfer and deformation. Seventeen candidates met the screening criteria. Ti-13Nb-13Zr showed an elastic modulus of about 80 GPa, and the titanium-based candidates showed deformation values of about 0.96 to 1.03 mm, whereas GF PEEK reached about 1.74 mm. The stress shielding index also showed that titanium-based materials remained on the implant-dominant side, while polymer-based materials shifted stress transfer toward bone. Taken together, the findings suggest that Ti-13Nb-13Zr offers the best overall balance for load-bearing sternal reconstruction, whereas PEEK-based systems may be more suitable within the present model for hybrid or adjunct designs. The proposed workflow can support early implant planning and guide future experimental and clinical studies.

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• MakaleYalnız künye2026Scopus SJRQ2/r/bayburt/11048
  Effect of Erbium Addition to A380 Aluminum Alloy on Mechanical and Microstructural Properties

  Gültekin, Çağrı; Çolak, Murat; Tabak, Yasemin; Şensoy, Abdullah Tahir

  There are many studies on improving the properties of aluminum alloys, but the addition of rare earth elements occupies a particularly important place among them. In this study, the effect of erbium (Er) addition on the microstructure and mechanical properties of A380 aluminum casting alloy was systematically investigated. A series of alloys with varying Er contents (0.03%, 0.05% and 0.1 wt.%) was fabricated using the conventional casting method. The addition of Er led to significant grain refinement, primarily due to the formation of Al3Er intermetallic particles, which acted as potent nucleation sites during solidification. Optical microscopy and SEM analyses confirmed the morphological transformation of the eutectic silicon phase into a finer and more fibrous structure. Mechanical testing revealed that the alloy containing 0.1 wt.% Er exhibited the highest ultimate tensile strength (236 MPa), elongation (4.56%), and hardness (87.6 HB), indicating an optimal balance between strength and ductility. The improvement is attributed to both microstructural refinement and dispersion strengthening mechanisms. These results suggest that controlled Er addition can be an effective strategy for enhancing the performance of cast Al–Si alloys, making them promising candidates for demanding structural applications in the automotive and aerospace industries.

  AtıfScopus3·WoS1

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• MakaleAçık Erişim2026Scopus SJRQ2/r/bayburt/10952
  Microstructural Evolution of Vanadium-Modified A380 Aluminum Alloy under Different Solidification Conditions

  Çolak, Murat; Avci, Ömer; Demir, Muhammet Emin

  Quality requirements for aluminum alloys are continuously increasing with technological advancements, driving the need for improved alloy design and casting control. Alloying additions and solidification conditions play a decisive role in determining the microstructural characteristics of cast aluminum alloys. In this study, a commercial A380 aluminum alloy was modified with vanadium (V) additions of 0.03, 0.06, and 0.1 wt.% and cast in step permanent molds with section thicknesses ranging from 5 to 30 mm, enabling a systematic investigation of different solidification conditions. Melting, liquid metal treatment, metallographic preparation, SEM/EDS analysis, density measurements, and solidification modeling were employed. The results demonstrate that vanadium addition and solidification time jointly govern the morphology and distribution of eutectic silicon and intermetallic phases. Under the investigated casting conditions, a V addition of 0.06 wt.% resulted in the most homogeneous microstructure, while higher V content led to the formation of coarser intermetallic phases, particularly at longer solidification times. These findings emphasize the importance of considering the combined effects of alloying and solidification parameters when optimizing the microstructure of A380 aluminum castings for industrial applications.

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