Person: BOZTOPRAK, YALÇIN
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BOZTOPRAK
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YALÇIN
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Publication Open Access Bor Nitrür Partikülleriyle Takviye Edilmiş Vinil Ester Matrisli_x000D_ Kompozitlerin Mekanik Özelliklerinin İncelenmesi(2019-01-31) KARTAL, İLYAS; İLYAS KARTAL;Yalçın BOZTOPRAKSon yıllarda inorganik partiküllerle takviyelendirilmiş polimer matrisli kompozitler yaygın bir şekildekullanılmaktadır. Yapılan çalışmaların birçoğu, polimer malzemelere inorganik yapıların ilavesiyle elde edilenhibrid malzemeler üzerine yoğunlaşmıştır. Bu çalışmada, bor nitrür partikül takviyeli vinil ester kompozitmalzemeler üretilmiştir. Matris malzemesi olarak vinil ester reçinesi kullanılmıştır. Takviye malzemesi olarakise ortalama 70 nm boyutlarında olan hegzagonal bor nitrür partikülleri kullanılmıştır. Farklı oranlarda üretilenbor nitrür takviyeli vinil ester kompozit numunelerin çekme dayanımı, eğilme dayanımı, darbe dayanımı, aşınmadayanımı ve sertlik özellikleri incelenmiştir. Test numunelerini hazırlamak için kalıp malzemesi olarak silikontercih edilmiştir. Reaksiyon başlatıcı olarak %50 aktif metil etil keton peroksit, hızlandırıcı olarak ise % 6’lıkkobalt naftalat kullanılmıştır. Partiküllerin homojen dağılımını sağlamak ve topaklanmayı engellemek içinpartikül miktarının 5 katı oranında MEG (mono etilen glikol) ilavesiyle elde edilen karışım, ultrasonik karıştırıcıiçerisinde 30 dakika karıştırılmıştır. Vinil ester reçine içerisine bor nitrür ilavesi işlemine ağırlıkça % 0,5oranından başlanmış ve % 2’ye kadar devam edilmiştir. Elde edilen kompozit malzemenin darbe ve sertlikdeğerlerinde artış görülmüştür. Çekme, % uzama ve eğilme özelliklerinde azalma gözlemlenmiştir. Aşınmamiktarında ise azalma, dolayısıyla aşınma dayanımında artış olduğu görülmüştür.Publication Open Access Sound insulation performance of honeycomb core aluminum sandwich panels with flexible epoxy-based foam infill(2023-09-01) BOZTOPRAK, YALÇIN; BOZTOPRAK Y., Ünal M., Özada Ç., Kuzu E., ÖZER H., Ergin F., YAZICI M.The most distinctive features of sound insulation structures are their flexibility and porosity. Therefore, the flexible epoxy matrix material was made cellular using a suitable foaming agent. In addition, hollow glass microspheres (HGMs) were added to the epoxy matrix. Thus, the sound wave refraction was increased by obtaining cavities in the cell walls. Structures with different densities and voids were created by changing the ratios of the filling material and foaming agents used in the sandwich. An aluminum (Al) honeycomb was used to protect the insulation materials\" structural integrity and ensure the homogeneous distribution of sound waves. The effect of density differences on sound insulation values was investigated. The mechanical properties of sandwich structures were determined using compression and three-point bending tests. The distribution of the filler in the matrix was visualized using SEM. TGA, DSC, thermal conductivity, dielectric, and flammability tests were also performed to determine their thermal, electrical, and flammability properties. During the formation of cells in the flexible epoxy, the HGMs were positioned in the cell wall by internal gas pressure. Low-density structures performed better at low frequencies, while high-density structures at high frequencies.Publication Metadata only Synthesis and characterization of UV-curable cellulose acetate butyrate-based oligomers and their cotton fabric coatings(SPRINGER, 2021) BOZTOPRAK, YALÇIN; Dehmen, Ozan Gazi; Onen, Hacer Aysen; Yildiz, Zehra; Gungor, Atilla; Boztoprak, YalcinIn order to improve the thermal stability and flexibility, cellulose acetate butyrate (CAB) was modified with toluene diisocyanate-hydroxyethyl methacrylate (TDI-HEMA) adduct in various molar ratios. The obtained oligomer was characterized by proton nuclear magnetic resonance (H-1 NMR) and Fourier transform infrared (FTIR) spectroscopies. Gloss, cross-hatch, contact angle, and Taber abrasion tests were all used to investigate the film forming performance of the modified CAB oligomers on glass plates. The UV-cured free films of the synthesized oligomers were examined in terms of the mechanical tests. By using the synthesized CAB oligomers, coating formulations were prepared and applied onto cotton fabrics in order to make the cotton fabrics more durable in outdoor environments. The existence of the coating layer on the fabric surfaces was investigated by scanning electron microscopy (SEM). The coated UV-cured fabrics were evaluated separately in terms of abrasion, thermal conductivity, and air and water vapor permeability properties. Results proved that the oligomer (50%-CAB) in which 50% of the hydroxyl groups of CAB were reacted with TDI-HEMA adduct showed the best mechanical properties with the highest tensile strength and modulus values. Considering the coated fabrics, the least deformation against abrasion, the highest air/water vapor permeability, and the best thermal conductivity were all recorded in 50%-CAB coated sample.Publication Metadata only Mechanical properties of double and triple fibre-reinforced epoxy hybrid composites(ICE PUBLISHING, 2020) BOZTOPRAK, YALÇIN; Boztoprak, YalcinA composite material can be defined as a combination of two or more materials that provide better properties than the material used alone. Composite materials can be preferred because of their many advantages - for example, they are stronger and lighter compared with conventional materials. Usage of fibre-reinforced composite structures has increased in industries such as automotive, marine transportation, civil engineering, sporting goods, medical equipment and prosthetic devices.Publication Metadata only Graphene oxide-containing isocyanate-based polyimide foams: Enhanced thermal stability and flame retardancy(WILEY, 2021) ÇAKIR, MUSTAFA; Cakir, Mustafa; Kilic, Volkan; Boztoprak, Yalcin; Ozmen, Fadime KaraerIsocyanate-based graphene oxide-containing polyimide foams were synthesized by a semi-prepolymer method. In this method, while the first solution containing pre-polymer was derived from pyromellitic dianhydride and excess polymethylene polyphenylene isocyanate (PM200), the second solution contains dianhydride derivatives, water, catalysts, surfactants, and graphene oxide. PIFs were prepared with 0%, 0.25%, 0.50%, 0.75%, and 1% graphene oxide by weight, respectively. PIFs exhibited a minimum side reaction and urea generation was not seen for all PIFs instead of imide bonding. The addition of graphene oxide (GO) leads to a more close-packed structure. Therefore, crosslinking density and thermal stability of graphene oxide-containing polyimide foams increased. Upon the addition of 1% GO, almost seven times higher compression strength was obtained compared to neat PIFs. Also, LOI values supported the theory that thermally stable and flame retardant PIFs can be synthesized via the isocyanate-based process with GO.Publication Metadata only Investigation of crack detection properties of elastomer-based nanocomposites under cyclic strain loading with graphene and carbon black interaction filler(2022-01-01) BOZTOPRAK, YALÇIN; Kasim H., BOZTOPRAK Y., YAZICI M.In this study, the synergistic effect created by adding Graphene (GE) nanoplatelets and carbon black (CB) fillers to the rubber matrix was used to determine the high stretchable sensor properties. GE and CB-filled rubber nanocomposite (HcN) strain sensors have been shown to detect and trace crack initiation and crack propagation of different sizes under cyclic loading. Tests were performed with four different crack sizes (0, 2.5, 5, and 10 mm) at five different strain levels (0%, 5%, 10%, 15%, and 20%) to determine the strain sensing performance of the specimens. The electrical response of HcNs under loading was measured with the four-point probe technique and recorded with a high-performance data acquisition system. The progression of external cracks created by scalpel on HcNs was examined by measuring electrical resistance changes caused by cyclic strain loading between 0% and 20%. The electrical response of 4 phr and 8 phr filled HcNs behaved qualitatively similar to each other, while 1 phr filled HcNs showed a significantly different response in terms of quality and quantity. In 4 phr GE-filled specimens, the resistance increase was changed steadily depending on the crack length, and unstable conditions occurred at 5 and 10 mm crack lengths at 1 and 8 phr GE filler ratios. The flexible and stretchable elastomer-based conductive strain sensing sensors, developed with the synergistic interaction of well-dispersed carbon-based fillers in the matrix, can detect and record damaged conditions caused by cyclic loading in many application areas.