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Öğe Usage of 3D Printed Polylactic Acid as a Core Material in Forming of Carbon Fiber Fabric Composite(Ege Üniversitesi, 2023) Kaya, Onur; Gümüş, Ömer Yunus; Küçük, İsrafil; Aslan, SerdarThe weak bonds between the layers of a part produced by the Fused Deposition Modeling (FDM) method causes damage at an early stage. To overcome the strength problem, FDM parts are manufactured with engineering thermoplastics or reinforced with carbon/glass fiber. Although these studies provided partial improvement on the mechanical strength of the part, the bond strength between the layers was not significantly improved. In this study, we aimed to reduce the negative effect of the weakness in the interlayer bond strength on the strength of the final part. Therefore, a composite laminate was applied on a polylactic acid (PLA) core produced by the FDM method. Weight measurement, tensile test, three-point bending test and weight drop test were performed on the produced test samples. Tensile and bending test results indicates that the composite layer applied on the core produced by the FDM method has a positive effect on the mechanical strength and bending properties. It is concluded that the study will be a source for future research on moldless composite production.Öğe Başlıksız(Springer, 2021) Uranbey, Leyla; Unal, Halil Ibrahim; Calis, Gokce; Gümüş, Ömer Yunus; Katmer, Sukran; Karatas, CetinShape memory polymers are the materials that can recover their original shape after a large deformation when exposed to an external stimulus such as electric field, pH, temperature, light, magnetism or humidity. With these properties, it is possible to use them in many areas in the industry. In this study, a shape-memory polymer compound was developed which is capable of changing its shape when subjected to an external voltage. Electroactive shape memory polymer compound was prepared by mixing commercially available and economically viable thermoplastic shape memory polyurethane (SMPU) with carbon black (CB), which has low cost and high electrical conductivity, by adding at various proportions. Conductivity, structural, morphological, homogeneity, thermal, rheological and shape memory characterizations of the SMPU/CB blend were carried out by four-probe measurements, ATR-FTIR spectroscopy, x-ray diffraction analysis, scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analyses, melt flow index (MFI), and a thermal camera imaging methods, respectively. The effects of CB loading ratios on these characteristics of SMPU/CB blends were investigated. It was concluded that SMPU/20CB blend can be used as a commercial material having shape memory characteristics.Öğe Başlıksız(Springer, 2019) Gümüş, Ömer Yunus; Unal, Halil IbrahimZinc borate (ZB) particles dispersed in silicone oil (SO) at concentrations of phi = 5vol%-20vol% were subjected to dielectric analysis to elucidate their polarization strength, time, and mechanism. Results revealed that all virgin dispersions lacked polarization. Triton X-100, a non-ionic surfactant, was added to ZB/SO dispersions to enhance the polarizability of ZB particles. The addition of 1vol% Triton X-100 enhanced the polarizability of ZB/SO dispersions, and the 15vol%ZB/SO system provided the highest dielectric difference Delta epsilon ' (the difference in epsilon ' values at zero and infinite frequency, Delta epsilon ' = epsilon(0) - epsilon(221D)) of 3.64. The electrorheological (ER) activities of the ZB/SO/Triton-X dispersion system were determined through the ER response test, and viscoelastic behaviors were investigated via oscillation tests. A recoverable deformation of 36% under an applied electrical field strength of 1.5 kV/mm was detected through creep and creep recovery tests.Öğe Başlıksız(Wiley-V C H Verlag Gmbh, 2016) Ozkan, Seyma; Gümüş, Ömer Yunus; Unal, Halil IbrahimElectric field stimulus fluids are prepared by dispersing poly(3-aminophenylboronic acid, PABA) and poly(thiophene-3-boronic acid, PTBA) nanoparticles in silicone oil (SO). Upon addition of a nonionic surfactant, Triton X-100, to the fluids, enhanced polarizabilities are detected on dielectric analysis which is driven by the increased number of dipole centers in their structures. Very high colloidal stability is observed for PABA/SO/Triton-X dispersion system since it has zeta(zeta)-potential value in colloidally stable region, whereas PTBA/SO/Triton-X dispersion system exhibits some degree of sedimentation due to low zeta-potential value. When electric field strengths are applied, increased yield stresses of the dispersions are detected. Storage and loss moduli values of PABA/SO/Triton-X and PTBA/SO/Triton-X dispersions suggest that the suspensions have vibration damping capabilities. Further, reversible non-Newtonian viscoelastic deformations are observed from the creep-recovery tests of the systems and they are classified as smart materials. Furthermore, the results show that PABA based colloidal system has better dielectric and rheological properties than that of PTBA and these results are also discussed in terms of particle conductivity and molecular structure.Öğe Başlıksız(GAZI UNIV, 2022) Gümüş, Ömer Yunus; İsmahane, YssaadPropolis has biological activity due to its wide variety of phenolic compound content. Propolis usage in many areas such as cosmetics, food, medicine, and biomedicals is becoming widespread day by day due to its antibacterial, antifungal, antiviral properties. In this study, phenolics extracted from propolis were covalently bonded and immobilized on the surface of polyethylene terephthalate (PET) fabric with the aim of developing a technical textile for biomedical applications. To do so, PET fabric was aminated, and then the phenolics were immobilized using polyethylene glycol diglycidyl ether (PEGDGE) as the crosslinking agent. Formation of amine groups in PET structure and immobilization of the phenolics were proved by ATR-FTIR spectrums. Water contact angle of PET being 121 degrees decreased to 110 degrees and 97 degrees after the amination and the immobilization, respectively. Optical microscope images were taken to monitor morphological changes after the processes. DSC results revealed a new endothermic peak at around 40 degrees C for modified PET. Tensile tests showed that tensile strength of the fabric weakens upon modification, while a healing effect occurs during immobilization. Antibacterial tests revealed that propolis extract immobilized fabric has an antibacterial activity against gram negative (E. coli) bacteria.Öğe Başlıksız(2019) Aydın, Hurşit Sefa; Gümüş, Ömer Yunus; Küçük, İsrafilSon yıllarda 3B baskı teknolojileri sahip olduğu yüksek üretim hızı, uygun maliyeti ve biyouyumlu malzeme üretimine imkan veren özellikleriyle yapay organ geliştirme alanına önemli yenilikler getirmiştir. Bu çalışmada, eriyik yığma modellemesi (EYM) özelliğine sahip bir 3B yazıcı kullanarak poliüretan (PU) polimeriyle hacimsel olarak farklı doluluk oranlarında (%25, %50, %75 ve %100) yapay insan kulak kepçesi üretimi gerçekleştirilmiştir. Kimyasal yapı analizleri için Fourier dönüşümlü kızılötesi (FTIR) spektroskopisi, termal analizler için termogravimetrik analiz (TGA) cihazı, yüzey görüntülerini incelemek için stereomikroskop ve taramalı elektron mikroskobu (SEM), mekanik ölçümler için sertlik ve çekme testi cihazları kullanılmıştır. Geliştirilen yapay kulak kepçelerinden en uygun tasarımın %50 doluluk oranına sahip olan kulak tasarımı olduğu belirlenmiştir.Öğe Başlıksız(SPRINGER, 2022) Gümüş, Ömer Yunus; İlhan, Recep; Canlı, Berat EnesMaterial extrusion (ME) is one of the additive manufacturing methods and widely used to produce polymer-based parts. Thermoplastic polyurethane (TPU) is a relatively new material in ME. It has microdomains consisting of hard segments (HS) and soft segments (SS) in varying proportions. This structural complexity and weak interactions between HS and SS cause the properties of TPUs to become very sensitive to processing parameters such as temperature. In this study, the effect of printing temperature in a range of 170-250 degrees C on the physical, mechanical, and viscoelastic properties of ultra-flexible TPU (Shore A 60) samples was investigated. Furthermore, to elucidate the effect of the manufacturing method, a sample prepared by compression molding (CM) at 230 degrees C was used. Thermal transitions of the samples were analyzed by DSC. Increasing T-g values were observed in correlation with increased printing temperature. A relation between T-g and hardness values was thus established. In order to observe molecular weight (M) changes after printing, zero shear viscosities (eta(0)) of polymer solutions were examined and preserved M values up to 200 degrees C were detected. Mechanical properties of the samples were analyzed through tensile tests. Among the samples including CM, the highest tensile strength and elongation at break were 37.6 MPa and 921%, respectively, which was detected for the sample printed at 230 degrees C. Oscillation tests revealed that both entanglements and HS content influence storages modulus (G '). Among the printed parts, highest G ' value was measured at 220 degrees C printing temperature. This result was attributed to the synergistic effect of entanglement and HS. Furthermore, it is concluded that chain alignment has greater contribution on mechanical properties than M, whereas viscoelastic properties is more sensitive to M.Öğe Başlıksız(John Wiley and Sons Ltd, 2021) Mallem O.K.; Zouai F.; Gümüş, Ömer Yunus; Benabid F.Z.; Bedeloğlu, Ayşe; Benachour D.This study aims to develop poly(vinyl chloride) (PVC) composites prepared by melt mixing by using a combination of talc and calcined kaolin as filler in order to improve the disadvantages of rigid PVC, which is widely used in industry, such as poor mechanical properties and low thermal stability. In addition, PVC/talc and PVC/calcined kaolin composites were also examined for comparison. The calcined kaolin is modified with urea to increase the surface area (chemical treatment), while the surface of both fillers is coated with stearic acid for good compatibility with PVC (mechanical treatment). Scanning electron microscopy micrographs showed homogeneous distribution of mechanically processed fillers. Attenuated total reflectance–Fourier-transform infrared spectroscopy analysis revealed successful coating of the fillers with stearic acid. Also, new bands were detected in the spectrum of urea-treated calcined kaolin, showing an effective chemical treatment. It has been observed that the treatment of fillers improves the mechanical properties of PVC. Thermogravimetric results showed that delaminated calcined kaolin increased the thermal stability of PVC composites. The results of this study proved that binary filler composites combine good properties of both (synergistic effect) and good filler dispersion can be obtained by using stearic acid and urea.
