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Öğe Effects of seawater corrosion environment on the impact behavior of multi-walled carbon nanotube and SiO2 reinforced basalt/epoxy hybrid nanocomposites(Sage Publications Ltd, 2022) Demirci, Ibrahim; Avci, AhmetIn this study, the impact behaviors of nano silica (SiO2 nanoparticles), MWCNTs (multi-walled carbon nanotube), and SiO2+MWCNTs (nano silica vs multi-walled carbon nanotube hybrid) nanoparticle additives in basalt fiber reinforced composites exposed to seawater corrosion were investigated. The Mediterranean was chosen as the corrosive sea water due to its high salinity. Basalt fiber reinforced composites immersed in seawater have quick mass absorption during the first 30 days. However, it can also vary between the first 28 and 40 days depending on the structure of the composite and environmental conditions. Immersion times were determined as 0, 10, 20, and 40 days. Tensile and low velocity impact tests were performed to evaluate the mechanical performance after seawater corrosion. Low velocity impact tests were carried out at 10 and 20 J energy levels. The aim of this study was to examine the effects of corrosion caused by quick mass absorption on the tensile and impact behaviors of basalt fiber reinforced composites. And also to investigate the contribution of SiO2 and MWCNT nanoparticle additives to the mass absorption mechanism and mechanical performance of basalt fiber reinforced composites. SiO2 and MWCNT nanoparticle additives increased the tensile and impact strength of basalt fiber reinforced composites. However, the tensile and impact behaviors of nanoparticle filled and nanoparticles unfilled basalt fiber reinforced composites were adversely affected by the seawater corrosion environment. Due to the geometric structure of SiO2 nanoparticles, the best mechanical performance was observed in SiO2 filled basalt fiber reinforced composites.Öğe Fracture toughness (Mode I) characterization of SiO2 nanoparticle filled basalt/epoxy filament wound composite ring with split-disk test method(Elsevier Sci Ltd, 2017) Demirci, Mehmet Turan; Tarakcioglu, Necmettin; Avci, Ahmet; Akdemir, Ahmet; Demirci, IbrahimMatrix cracking which is the major initial form of damage in fiber reinforced polymer composites plays significant role in determining the fracture toughness. The fast crack propagation in polymer matrix causes to decrease the fracture toughness of fiber reinforced polymer (FRP) composite. In order to retard the fast crack propagation in polymer matrix and provide to increase of the fracture toughness of FRP composite, the polymer matrix of FRP composite is modified by filling the different kinds of nano particles. In such a way, the crack propagation leads to retard and dissipate the stress concentration affected to form the fiber cracks along of fibers in composite structure. In this study, basalt fiber was used as reinforcement material in +/-[55]6 filament wound ring composite for creating the alternative to carbon, kevlar and glass fibers, to contribute to the research studies and literature. SiO2 nanoparticles that provides to form the effects of fracture toughness mechanism based on the effect of retarding crack propagation were filled into epoxy matrix to increase the mechanical properties and fracture toughness of +/-[55]6 filament wound BFR/Epoxy ring composite. The split-disk tensile tests of single edge notched and un-notched +/- 155]6 filament wound BFR/Epoxy ring composite specimens were conducted to determine the mechanical properties and mode I fracture toughness. SiO2 nanoparticle addition into epoxy matrix of +/-[55]6 filament wound BFR/Epoxy ring composites has given the results of hoop tensile stress within the range of 27.7-30.3%. The fracture toughness of composite ring specimen was specified by ASTM E 399-12E3 by adapting to the directed mode I crack propagation and compared with each other. An effective increase in mode I fracture toughness of 43%-50% was obtained at 4 wt% addition level of SiO2 nanoparticles. The crack branching in epoxy matrix provided by SiO2 nanoparticle, matrix cracking, debonding, delamination and fiber breakage failures has been observed via microscope and SEM analysis. (C) 2017 Elsevier Ltd. All rights reserved.Öğe Impact of Obesity on the Metabolic Control of Type 2 Diabetes: Results of the Turkish Nationwide Survey of Glycemic and Other Metabolic Parameters of Patients with Diabetes Mellitus (TEMD Obesity Study)(Karger, 2019) Sonmez, Alper; Yumuk, Volkan; Haymana, Cem; Demirci, Ibrahim; Barcin, Cem; Kiyici, Sinem; Guldiken, SibelBackground: Obesity is the main obstacle for metabolic control in patients with type 2 diabetes. Turkey has the highest prevalence of obesity and type 2 diabetes in Europe. The effect of obesity on the metabolic control, and the macro-and microvascular complications of patients are not apparent. Objectives: This nationwide survey aimed to investigate the prevalence of overweight and obesity among patients with type 2 diabetes and to search for the impact of obesity on the metabolic control of these patients. We also investigated the independent associates of obesity in patients with type 2 diabetes. Methods: We consecutively enrolled patients who were under follow-up for at least 1 year in 69 tertiary healthcare units in 37 cities. The demographic, anthropometric, and clinical data including medications were recorded. Patients were excluded if they were pregnant, younger than 18 years, had decompensated liver disease, psychiatric disorders interfering with cognition or compliance, had bariatric surgery, or were undergoing renal replacement therapy. Results: Only 10% of patients with type 2 diabetes (n = 4,648) had normal body mass indexes (BMI), while the others were affected by overweight (31%) or obesity (59%). Women had a significantly higher prevalence of obesity (53.4 vs. 40%) and severe obesity (16.6 vs. 3.3%). Significant associations were present between high BMI levels and lower education levels, intake of insulin, antihypertensives and statins, poor metabolic control, or the presence of microvascular complications. Age, gender, level of education, smoking, and physical inactivity were the independent associates of obesity in patients with type 2 diabetes. Conclusion: The TEMD Obesity Study shows that obesity is a major determinant of the poor metabolic control in patients with type 2 diabetes. These results underline the importance of prevention and management of obesity to improve health care in patients with type 2 diabetes. Also, the results point out the independent sociodemographic and clinical associates of obesity, which should be the prior targets to overcome, in the national fight with obesity. (c) 2019 The Author(s) Published by S. Karger AG, BaselÖğe Investigation of nano-hybridization effects on low velocity impact behaviors of basalt fiber reinforced composites(Sage Publications Ltd, 2021) Demirci, Ibrahim; Avci, Ahmet; Demirci, Mehmet TuranIn general the nanoparticles increase the mechanical and impact behaviors of fiber reinforced polymer based composites. However, the effects of the hybridization of nanoparticles and their reasons over the nano scale fracture mechanisms have not been adequately studied for fiber reinforced composites. In this study, the low velocity impact responses and the mechanical behaviors were investigated for 4%wt. SiO(2)nanoparticles filled BFR/Epoxy nanocomposites, 0.5%wt. MWCNTs filled BFR/Epoxy nanocomposites, 4%wt. SiO(2)nanoparticles and 0.5%wt. MWCNTs nano-hybrid filled BFR/Epoxy nanocomposites and unfilled BFR/Epoxy composites. The tensile and low velocity impact tests at 10 J and 20 J of energy levels were applied to nanoparticles, nano-hybrid and unfilled BFR/Epoxy composites in order to define the effects of nanoparticles and nano-hybrid particles on the impact and mechanical features according to in accordance with ASTM D3039/D3039M-14 and ASTM D7136/7136M standards. It was observed that SiO(2)nanoparticles addition to BFR/Epoxy for both 10 J and 20 J showed the highest tensile strength, maximum force, rebound energy and the lowest displacements and absorbed energy. SiO2+MWCNTs nano-hybrid addition to BFR/Epoxy improved higher low velocity impact responses and tensile strength than MWCNTs addition. The specimens of unfilled BFR/Epoxy composites showed the lowest tensile strength and maximum force and the highest maximum force, displacements and absorbed energy. Microscope and SEM analyses demonstrated that minimum failures like fiber breakages, delamination and debonding were observed by filling SiO(2)nanoparticles provided the nano scale fracture mechanisms. In addition MWCNTs hybridization with SiO(2)nanoparticles minimizes negative effects of MWCNTs micro size length and improved the impact and mechanical behaviors.