Mechanical Engineering / Makina Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/4129
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Article Citation - WoS: 13Citation - Scopus: 16Influence of Recycled Carbon Fiber Addition on the Microstructure and Creep Response of Extruded Az91 Magnesium Alloy(KeAi Communications Co., 2023) Kandemir, Sinan; Bohlen, Jan; Dieringa, HajoIn this study, the recycled short carbon fiber (CF)-reinforced magnesium matrix composites were fabricated using a combination of stir casting and hot extrusion. The objective was to investigate the impact of CF content (2.5 and 5.0 wt.%) and fiber length (100 and 500 µm) on the microstructure, mechanical properties, and creep behavior of AZ91 alloy matrix. The microstructural analysis revealed that the CFs aligned in the extrusion direction resulted in grain and intermetallic refinement within the alloy. In comparison to the unreinforced AZ91 alloy, the composites with 2.5 wt.% CF exhibited an increase in hardness by 16–20% and yield strength by 5–15%, depending on the fiber length, while experiencing a reduction in ductility. When the reinforcement content was increased from 2.5 to 5.0 wt.%, strength values exhibited fluctuations and decline, accompanied by decreased ductility. These divergent outcomes were discussed in relation to fiber length, clustering tendency due to higher reinforcement content, and the presence of interfacial products with micro-cracks at the CF-matrix interface. Tensile creep tests indicated that CFs did not enhance the creep resistance of extruded AZ91 alloy, suggesting that grain boundary sliding is likely the dominant deformation mechanism during creep. © 2023Article Citation - WoS: 41Citation - Scopus: 45High Temperature Tensile, Compression and Creep Behavior of Recycled Short Carbon Fibre Reinforced Az91 Magnesium Alloy Fabricated by a High Shearing Dispersion Technique(National Engineering Research Center for Magnesium Alloys of China, Chongqing University, 2021) Kandemir, Sinan; Gavras, Sarkis; Dieringa, HajoThe present study seeks the feasibility of using short carbon fibres recycled from polymer matrix composites as alternative to virgin carbon fibres in the reinforcement of magnesium alloys. The microstructures, high temperature mechanical and creep properties of AZ91 alloy and its composites with various recycled carbon fibre contents (2.5 and 5 wt.%) and lengths (100 and 500 ?m) were investigated in the temperature range of 25–200 °C. The microstructural characterization showed that the high shear dispersion technique provided the cast composites with finer grains and relatively homogenous distribution of fibres. The materials tested displayed different behaviour depending on the type of loading. In general, while enhancements in the mechanical properties of composites is attributed to the load bearing and grain refinement effects of fibres, the fluctuations in the properties were discussed on the basis of porosity formation, relatively high reinforcement content leading to fibre clustering and interlayer found between the matrix and reinforcement compared to those of AZ91 alloy. The compressive creep tests revealed similar or higher minimum creep rates in the recycled carbon fibre reinforced AZ91 in comparison to the unreinforced AZ91. © 2021Article Citation - WoS: 4Citation - Scopus: 5Effects of Tib2 Nanoparticle Content on the Microstructure and Mechanical Properties of Aluminum Matrix Nanocomposites(Walter de Gruyter GmbH, 2017) Kandemir, SinanThe present work reports the fabrication of A357 alloy matrix nanocomposites reinforced with 0.5, 1.0 and 2.0 wt.-% TiB2 nanoparticles (20-30 nm) by a novel method which is the combination of semi-solid mechanical mixing and ultrasonic dispersion of nanoparticles in liquid state. The microstructural and mechanical properties of the fabricated nanocomposites were investigated. The microstructural studies conducted with optical and advanced electron microscopes indicated that reasonably effective deagglomeration and uniform distribution of TiB2 nanoparticles into the matrix were achieved. Transmission electron microscopy studies also confirmed that the nanoparticles were embedded into the matrix and a good bonding was obtained between the matrix and the reinforcement. Increasing nanoparticle content led to grain refinement and significant enhancement in the mechanical properties of nanocomposites. The addition of 0.5, 1.0, and 2.0 wt.-% TiB2 nanoparticles increased the 0.2 % proof stress of matrix alloy by approximately 31, 48 and 61 %, respectively. The contribution of different mechanisms to the strength enhancement is discussed. It is proposed that the strengthening is mainly due to Orowan mechanism and dislocation generation effect by the coefficient of thermal expansion mismatch between the TiB2 nanoparticles and the matrix.Article Citation - WoS: 16Citation - Scopus: 24Developing Polymer Composite-Based Leaf Spring Systems for Automotive Industry(Walter de Gruyter GmbH, 2018) Öztoprak, Nahit; Güneş, Mehmet Deniz; Tanoğlu, Metin; Aktaş, Engin; Eğilmez, Oğuz Özgür; Şenocak, Çiler; Kulaç, GedizComposite-based mono-leaf spring systems were designed and manufactured to replace existing mono-leaf metal leaf spring in a light commercial vehicle. In this study, experimentally obtained mechanical properties of different fiber-reinforced polymer materials are presented first, followed by the description of the finite element analytical model created in Abaqus 6.12-1 (Dassault Systemes Simulia Corp., RI, US) using the obtained properties. The results from the finite element analysis are presented next and compared with actual size experimental tests conducted on manufactured prototypes. The results demonstrated that the reinforcement type and orientation dramatically influenced the spring rate. The prototypes showed significant weight reduction of about 80% with improved mechanical properties. The hybrid composite systems can be utilized for composite-based leaf springs with considerable mechanical performance.Article Citation - WoS: 14Citation - Scopus: 16Microstructure and Mechanical Properties of A357/Sic Nanocomposites Fabricated by Ultrasonic Cavitation-Based Dispersion of Ball-Milled Nanoparticles(SAGE Publications Inc., 2017) Kandemir, SinanIn this work, A357/0.5 wt.% SiC nanocomposites were fabricated with a combination of ultrasonic processing and a nanoparticle feeding mechanism that involves the introduction of a closed end aluminium tube filled with the ball-milled SiC nanoparticles (20-30 nm) and aluminium powders (<75 μm) into the melt for complete deagglomeration and uniform dispersion of nanoparticles through the matrix. The microstructural and mechanical properties of the fabricated nanocomposites were investigated. The microstructural studies conducted with optical and advanced electron microscopes indicate that relatively effective deagglomeration and uniform dispersion of SiC nanoparticles into the molten alloy were achieved. The hardness and tensile properties of the nanocomposites were notably improved compared to those of the ultrasonically processed A357 alloy without reinforcement, showing the strengthening potency of nanoparticles and the good bonding obtained at the particle-reinforcement interface.Article Citation - WoS: 33Citation - Scopus: 41Development of Novel Multilayer Materials for Impact Applications: a Combined Numerical and Experimental Approach(Elsevier Ltd., 2009) Taşdemirci, Alper; Hall, Ian W.A well-verified and validated numerical model was used to investigate stress wave propagation in a multilayer material subjected to impact loading. The baseline material consisted of a ceramic faceplate and composite backing plate separated by a rubber or teflon foam interlayer: several variants were investigated in which the number, type, and total thicknesses of the interlayers were altered. Comparison of the variants showed that the use of multiple teflon foam interlayers could drastically reduce the average stress in the multilayer material. Based on the numerical results, further experimental work was undertaken upon one of the variants. Very large and unexpected tensile stress oscillations were observed in the ceramic layers, leading to a refinement of the numerical model which successfully reproduced the oscillations and also demonstrated that separation of the sample layers led to trapping of the stress wave within the layers. Use of the validated numerical model allowed detailed analysis of the processes of wave transmission and demonstrates the important synergy that can exist between experimental and modeling studies. The current study provides a valuable starting point for designing future multilayer materials with specific, controlled properties.Conference Object Effect of Blending Conditions on the Properties of Epdm/Organoclay Nanocomposites(IOM Communications Ltd., 2009) Karşal, Çiçek; Tanoğlu, Metin; Odabaş, Sibel; Ersoy, Osman G.; Karakaya, NurselThe effects of blending conditions on the microstructural and mechanical properties of EPDM / organo modified montmorillonite (OMMT) nanocomposites at various clay loadings were investigated. The effects of the processing conditions were manifested in both the morphology and mechanical properties, which showed significant increase when optimized process conditions are applied.Article Citation - WoS: 78Citation - Scopus: 106Critical Aspects Related To Processing of Carbon Nanotube/Unsaturated Thermoset Polyester Nanocomposites(Elsevier Ltd., 2007) Seyhan, Abdullah Tuğrul; Gojny, Florian H.; Tanoğlu, Metin; Schulte, KarlCarbon nanotubes (CNTs) have outstanding mechanical, thermal and electrical properties. As a result, particular interest has been recently given in exploiting these properties by incorporating carbon nanotubes into some form of matrix. Although unsaturated polyesters with styrene have widespread use in the industrial applications, surprisingly there is no study in the literature about CNT/thermoset polyester nanocomposite systems. In the present paper, we underline some important issues and limitations during the processing of unsaturated polyester resins with different types of carbon nanotubes. In that manner, 3-roll mill and sonication techniques were comparatively evaluated to process nanocomposites made of CNTs with and without amine (NH2) functional groups and polyesters. It was found that styrene evaporation from the polyester resin system was a critical issue for nanocomposite processing. Rheological behaviour of the suspensions containing CNTs and tensile strengths of their resulting nanocomposites were characterized. CNT/polyester suspensions exhibited a shear thinning behaviour, while polyester resin blends act as a Newtonian fluid. It was also found that nanotubes with amine functional groups have better tensile strength, as compared to those with untreated CNTs. Transmission electron microscopy (TEM) was also employed to reveal the degree of dispersion of CNTs in the matrix.Article Citation - WoS: 17Citation - Scopus: 20Numerical and Experimental Studies of Damage Generation in a Polymer Composite Material at High Strain Rates(Elsevier Ltd., 2006) Taşdemirci, Alper; Hall, Ian W.Samples of S2-glass/epoxy composites have been subjected to microstructural investigation after testing in compression at quasi-static and high strain rates using the split Hopkinson pressure bar. A numerical model was developed that accurately describes the high strain rate mechanical response of the samples. Moreover, in contrast with earlier phenomenological or constitutive models, the model can also predict a variety of failure modes such as delamination, matrix cracking or fiber crushing. High-speed photography was used to check the model results. Interrupted tests, followed by metallographic examination, have revealed that the sequence of damage events differs between quasi-static and high strain rate regimes. The effect of sample size on measured mechanical properties is noted and is confirmed via numerical modeling.Article Citation - WoS: 143Citation - Scopus: 164Mechanical and Thermal Behavior of Non-Crimp Glass Fiber Reinforced Layered Clay/Epoxy Nanocomposites(Elsevier Ltd., 2007) Bozkurt, Emrah; Kaya, Elçin; Tanoğlu, MetinMechanical and thermal properties of non-crimp glass fiber reinforced clay/epoxy nanocomposites were investigated. Clay/epoxy nanocomposite systems were prepared to use as the matrix material for composite laminates. X-ray diffraction results obtained from natural and modified clays indicated that intergallery spacing of the layered clay increases with surface treatment. Tensile tests indicated that clay loading has minor effect on the tensile properties. Flexural properties of laminates were improved by clay addition due to the improved interface between glass fibers and epoxy. Differential scanning calorimetry (DSC) results showed that the modified clay particles affected the glass transition temperatures (T g) of the nanocomposites. Incorporation of surface treated clay particles increased the dynamic mechanical properties of nanocomposite laminates. It was found that the flame resistance of composites was improved significantly by clay addition into the epoxy matrix.