Yazar "Oz, Yahya" seçeneğine göre listele

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    Investigation of thermoforming processes of aerostructures: Simulation and microstructural analysis
    (Springer London Ltd, 2024) Cobanoglu, Merve; Ece, Remzi Ecmel; Unlu, Busra; Oz, Yahya; Toros, Serkan; Ozturk, Fahrettin
    A series of experimental and numerical studies were carried out on the mechanical and geometric performance of an aerostructural part produced by a material out-of-autoclave stamp forming process using unidirectional (UD) carbon fiber (CF) reinforced polyetherketoneketone (PEKK), which provides advantages like reshaping, recycling, welding, and low serial manufacturing costs. As a novelty, initial part geometry, different types of springs, and their attachment type were examined experimentally and compared with simulations. Compression tests were performed to determine mechanical strengths which reach levels up to 550 MPa. In addition, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were conducted to determine the crystallinity which occurs depending on the cooling regimes of the material. The crystallinity has been observed to vary regionally ranging from 16 to 21%. However, the crystallinity of the part towards the cold mold region decreased from 20 to 17%. In addition, simulations were performed to observe and control the occurrence of wrinkles and other defects.
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    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, Yahya
    As 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.