Yazar "Tatar, Ahmet Caner" seçeneğine göre listele

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    Impact response of nanoparticle reinforced 3D woven spacer/epoxy composites at cryogenic temperatures
    (SAGE Publications, 2021) Yıldırım, Ferhat; Tatar, Ahmet Caner; Eskizeybek, Volkan; Avcı, Ahmet; Aydın, Mustafa
    Fiber-reinforced polymer composites serving in harsh conditions must maintain their performance during their entire service. The cryogenic impact is one of the most unpredictable loading types, leading to catastrophic failures of composite structures. This study aims to examine the low-velocity impact (LVI) performance of 3D woven spacer glass-epoxy composite experimentally under cryogenic temperatures. LVI tests were conducted under various temperatures ranging from room temperature (RT) to −196°C. Experimental results reveal that the 3D composites gradually absorbed higher impact energies with decreasing temperature. Besides, the effect of multi-walled carbon nanotube and SiO2 nanofiller reinforcements of the matrix on the impact performance and the damage characteristics were further assessed. Nanofiller modification enhanced the impact resistance up to 30%, especially at RT. However, the nanofiller efficiency declined with decreasing temperature. The apparent damages were visually examined by scanning electron microscopy to address the damage formation. Significant outcomes have been achieved with the nanofiller modification regarding the new usage areas of 3D woven composites.
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    Selectively Reinforced Functionally Graded Composite-like Glass/Carbon Polymer Nanocomposites: Designed for Efficient Bending and Impact Performance
    (Korean Fiber Society, 2022) Demir, Okan; Tatar, Ahmet Caner; Eskizeybek, Volkan; Avcı, Ahmet
    Offshore wind turbine blades (OWTBs) are exposed to various types of loadings during their service life. Moreover, due to their tremendous size, huge investment costs are established, including advanced engineering materials and production process solutions. To decrease their investment cost without sacrificing their mechanical performances, advanced engineering solutions in the view of material selection and design should be implemented. With this motivation, we aimed to develop a novel laminated composite design considering reducing investment costs without compromising the bending and impact resistance of an OWTB. For this, an efficient and cost-effective design of a functionally graded composite (FGM)-like glass/carbon fibers reinforced hybrid polymer composite with a specific stacking sequence was presented. To evaluate mechanical performance of the composite structure, tensile, flexural, and to simulate environmental conditions, low-velocity impact tests were conducted. Furthermore, multi-walled carbon nanotubes (MWCNTs) were also introduced into the polymer matrix to evaluate their effectiveness in the hybridized composite. Drastic improvements in the bending strength (55.8 %) and strain (39.7 %) were obtained compared to the neat carbon fiber reinforced epoxy composites (CFs), especially with the aid of MWCNTs. According to impact tests, it was pointed out that it is possible to obtain higher impact peak forces (around 15 %) compared to neat CFs. However, MWCNTs contributed with slight increments in impact resistance but effectively restricted the impact damage propagation. This study reveals it is possible to tune the bending performance, the absorbed energy, and the damage extension by utilizing glass and carbon fiber laminates in an FGM-like structure.