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Öğe E-camı/epoksi kompozit boruların darbe cevabına vurucu geometrisinin etkisi(2016) Uyaner, Mesut; Kara, MemduhBu çalışmada filaman sarım yöntemiyle üretilmiş 55 sarım açısına sahip 10 tabakalı E-camı/epoksi kompozit boruların düşük hızlı darbe cevabına vurucu geometrisinin etkisi deneysel olarak araştırılmıştır. V yatağı üzerine yerleştirilen kompozit boru numunelerine düşük hızlı darbe cihazı kullanılarak, 24 mm ve 12 mm çaplı yarı-küresel ve 120 piramit uca sahip vurucularla düşük enerjili darbe yapılmıştır. Düşük enerjili darbe deneyleri 5 J, 10 J ve 15 J enerji seviyelerinde yapılmıştır. Vurucu geometrisine ve enerji seviyesine bağlı olarak elde edilen kuvvet-zaman ve kuvvet yer değiştirme değişimleri incelenmiştir. Ayrıca farklı geometrilere sahip vurucuların kompozit boru numunesinde meydana getirmiş olduğu hasarlar haritalanmış, vurucu geometrisine bağlı olarak değişen hasar alanları tetkik edilmiştirÖğe The Effect of Hydrothermal Aging on the Low-Velocity Impact Behavior of Multi-Walled Carbon Nanotubes Reinforced Carbon Fiber/Epoxy Composite Pipes(Springer, 2021) Kara, Memduh; Ak, Safa; Uyaner, Mesut; Gunoz, Alper; Kepir, YusufChemical transmission lines, petroleum and natural gas lines, pressure vessels, and pipes used in thermal facilities are expected to maintain their mechanical properties for many years without being damaged and not to be corroded in working conditions. The composite materials are the right candidate for these harsh conditions due to their superior properties. Reinforcement of nanoadditives to composite materials improves both the mechanical properties and the resistance to environmental conditions, thereby increasing the lifetime. In this study, multi-walled carbon nanotube (MWCNT) reinforced [+/- 55 degrees] carbon fiber/epoxy composite pipes produced with filament wound method were used. It was hydrothermally aged in 80 degrees C distilled water for 1, 2, 3 weeks in order to examine the effect of environmental conditions. In order to investigate its resistance against loads that may occur in working conditions, ring tensile tests (ASTM D 2290-16 procedure A), and low-velocity impact tests at 5, 10, 15 J, energy levels were carried out. The effect of hydrothermal aging on neat and MWCNT added epoxy composite had been examined by considering the aging period. Consequently, the impact resistance of neat and MWCNT added samples decreased with the aging process. Besides, tangential tensile strength loss was 17% in MWCNT reinforced sample and 13% in the neat sample.Öğe Effects of extreme low temperatures on the impact behavior of boron nitride nanofillers added carbon fiber/epoxy composite tubes(Sage Publications Ltd, 2022) Kara, Memduh; Tatar, Ahmet Caner; Kirici, Muhammed; Kepir, Yusuf; Gunoz, Alper; Avci, AhmetThis study aims to investigate the low-velocity impact response of boron nitride nanoparticles (BNNPs) added carbon fiber reinforced pipes (CFRPs) at various temperature values. Carbon fiber/epoxy composite specimens with (+/- 55 degrees)(3) winding angles were manufactured with the filament winding method. Low-velocity impact tests were performed with a 15 J energy level at five different temperatures between -196 degrees C and 23 degrees C ranges to understand the cryogenic environment effect on BNNP added carbon fiber reinforced tubes and neat carbon fiber reinforced tubes. The force-displacement and contact force-time graphs were attained in consequence of low-velocity impact tests. The damage areas, their size and characteristics were scrutinized both visually and with the aid of a Microscope. The test results showed that when ambiance temperatures decreased, the damage areas considerably increased both filled with BNNP and without BNNP filament wound carbon fiber reinforced tubes.Öğe Effects of the number of fatigue cycles on the impact behavior of glass fiber/epoxy composite tubes(Elsevier Sci Ltd, 2017) Kara, Memduh; Kirici, MuhammedThis paper investigates the impact damage behaviors of filament wound glass reinforced plastic (GFRP) tubes that were fatigued under internal pressure. Damage to the GFRP tubes was investigated, and the tubes' bursting pressures were determined. (+/- 55 degrees)(3) E-glassfepoxy composite specimens were manufactured using the filament winding method. Fatigue tests were applied to the specimens at a stress rate of 0.05 and frequency of 0.42 Hz in accordance with the ASTM-D 2992 standard. The specimens were subjected to fatigue tests at a stress level of 35% static burst pressure. Fatigued and non-fatigued composite tube specimens were pre-stressed by applying 32 bar internal pressure. After applying internal pressure, low velocity impact tests at various energy levels (5 J, 10 J and 15 J) were performed on the GFRP tubes. Plots of contact force-time history were obtained. For impact characteristics, such as deflection, absorbed energies were calculated based on the force time histories. The damaged areas that developed on the specimens were also evaluated. The specimens that fatigued and impacted at the 10 J energy level burst in accordance with the ASTM D 1599 standard. It was concluded that for all of the energy levels employed in this work, as the number of fatigue cycle increases, the rigidity of the tubes decreases. (C) 2017 Elsevier Ltd. All rights reserved.Öğe Filaman Sarım ile Üretilen CTP Kompozit Borularda Tabaka Sayısının Teğetsel Gerilme Dayanımına Etkisi(2017) Kara, Memduh; Uyaner, MesutCam takviyeli plastik (CTP) kompozit boruların diğer boru çeşitlerine göre birçok üstün özelliği vardır. Bunlar, kimyasal maddelerin oluşturacağı korozyona karşı dayanım, olumsuz hava koşullarına ve UV ışınlara karşı dayanım, istenilen boyutlarda seri üretim imkânı ve uzun ömürlü olması gibi özelliklerdir. Bütün bu özellikleri nedeniyle petrol ve doğalgaz iletim hatlarında ve kimyasal akışkanların iletim hatlarında yaygın olarak kullanılmaktadır. Kullanım alanı hızla artmakta olan CTP kompozit boruların mekanik özelliklerinin belirlenmesi için birçok test yöntemi geliştirilmiştir. Cam takviyeli plastik boruların teğetsel gerilme dayanımı; ASTM D 1599 standardına göre hidrolik basınç testi ve ASTM D 2290 standardına göre halka çekme testi ile tespit edilmektedir. Bu çalışmada 6, 8 ve 10 tabakalı olacak şekilde filaman sarım yöntemiyle 55 sarım açısında üretilen Ecamı/epoksi kompozit boruların teğetsel gerilme dayanımı her iki yöntem kullanılarak belirlenmiştir. Her iki yöntemden elde edilen sonuçlar birbirleriyle karşılaştırılarak değerlendirilmiştir. Ayrıca CTP kompozit borularda statik iç basınç patlatma testi esnasında ve halka çekme testi esnasında oluşan hasar gelişimi değerlendirilmiştir.Öğe Low velocity impact response and damages of GFRP composite tubes under room and cryogenic temperatures(Sage Publications Ltd, 2021) Kara, Memduh; Arat, Mustafa; Uyaner, MesutIn this paper, we have investigated the damages of glass fiber reinforced plastic (GFRP) composite tubes under the effect of low-velocity impact (LVI) at cryogenic environment conditions and room temperature. A GFRP composite tube consists of 6 layered E-glass/epoxy samples with a +/- 55 degrees winding angle, which produced by the filament winding method. Composite tubes either at room temperature or conditioned by liquid nitrogen at different temperature values (273 K, 223 K, 173 K, and 77 K) were impacted at 5, 7.5, and 10 J. Also, force-time and force-displacement graphs were plotted. The damaged regions of the samples were scrutinized. The damage areas of the GFRP composite tubes were smaller as the temperature decreased. However, the energy absorbed at low-temperature conditions was slightly higher than that absorbed in room temperature. Besides, no micro-cracks developed in the composite tubes after cryogenic conditioning.Öğe Low velocity impact response of prestressed functionally graded hybrid pipes(Elsevier Sci Ltd, 2016) Gemi, Lokman; Kara, Memduh; Avci, AhmetFilament wound hybrid composite pipes are frequently used for the transmission of high pressured chemical fluids, disposal of industrial wastes, oil and natural gas transmission lines. In this study, low velocity impact behavior of the glass/carbon functionally graded filament wound composite pipes with 55 winding angle was experimentally investigated. The hybrid composite pipes were graded with a fixed layer configuration from inside to outside as glass-glass/glass-carbon/carbon-glass/carbon-carbon. The functionally graded hybrid pipes were subjected to different internal pressure values (4, 16 and 32 bar), and impact response and energy absorption capacity of the hybrid composite pipes were investigated by using weight drop test method with impact energies of 5, 10, 15 and 20 J. The impact force and displacement versus interaction time were measured. The impulsive force, energy absorption capability, and damage formation were also investigated. Delamination, radial and surface Matrix crack formations were observed as the main failure mechanisms at the outer surface of the hybrid pipes. Moreover, the effect of impact damage decreased with the increasing internal pressure of the prestressed hybrid composite pipes. The impact damaged composite pipes were subsequently subjected to burst tests according to ASTM D1599-99 standards to calculate burst strengths of the damaged composite pipes. The hybrid composite pipes subjected to 32 bar internal pressure before impact loading were exhibited highest burst strengths for the same impact energy levels. (C) 2016 Elsevier Ltd. All rights reserved.Öğe Low-energy repeated impact response of nanoparticle reinforced carbon fiber epoxy composite pipes(Elsevier Sci Ltd, 2022) Kara, Memduh; Nomer, Anil Erdag; Kepir, Yusuf; Gunoz, Alper; Avci, AhmetFiber reinforced composite pipes, which are generally used to transport petroleum, natural gas, chemical liquids, and gases can be subjected to single or repeated low-energy impact loads under service conditions. Composites are materials that are highly sensitive to impact. For this reason, when they are exposed to low-energy impact, damages occur on the material that is difficult to prevent. The composite structure is reinforced by using nanoparticles in order to reduce these damages on the material and therefore increase the impact resistance of fiber reinforced composite pipes. In this study, filament wound carbon fiber epoxy composite pipes were reinforced with multi-walled carbon nanotubes (MWCNTs) and boron nitride nanoparticles (BNNPs). In order to examine the repeated impact response of the produced neat and reinforced pipes, repeated impact tests were carried out at different energy levels (10, 15 and 20 J). Damage mechanisms due to repeated impact were investigated. As a consequence of the experiments, it was concluded that the nanoparticle reinforcement increased the energy absorption capacity of the composite materials and significantly reduced the damage to the materials.Öğe Metal tabakalı kompozitlerin düşük hızlı enine darbeye karşı davranışlarının incelenmesi(2016) Kara, Memduh; Uyaner, MesutBu çalışmada metal kompozit levhaların düşük hızlı enine darbe davranışları incelenmiştir. 1 mm kalınlığında St37 DKP çelik ve 1050-H14 alaşımlı alüminyum plakalar kullanılarak dört farklı yerleşim düzeninde oluşturulan üç katmanlı kompozit levhalar farklı enerji seviyelerinde düşük hızlı darbe testlerine maruz bırakılmışlardır. 150x150 mm ebatlarında kesilen metal levhalar üç alüminyum, üç çelik, aliminyumçelikalüminyum ve çelikalüminyumçelik olacak şekilde dizilerek dört tarafı ankastre olacak şekilde bağlanmıştır. Deneylerde kullanılan vurucu kütlesi 6,35 kg olup 24 mm yarı küresel geometriye sahiptir. Hazırlanan her bir deney numunesinin ortasına 10J, 20J, 30J, 40J ve 50J enerji seviyelerinde darbe testleri yapılmıştır. Darbe testleri sonucu elde edilen kuvvet-zaman, hız-zaman ve kuvvet-yer değiştirme değişimleri grafikler halinde incelenmiştir. Her bir deney numunesinde meydana gelen hasarların boyutları ve hasar şekilleri değerlendirilmiştir.Öğe Repairing impact damaged fiber reinforced composite pipes by external wrapping with composite patches(Elsevier Sci Ltd, 2015) Kara, Memduh; Uyaner, Mesut; Avci, AhmetRepairs made with composite patches on impact damaged fiber reinforced composite pipes offer distinct advantages over traditional repairs in addition to reduced cost. In this study, effects of number of patch layers on the burst pressure of low velocity impact damaged tubes that have been repaired with composite patches were investigated. The tubes were pressurized up to 32 bar prior to impact. The pre-stressed glass fiber reinforced plastic tubes were damaged by applying low velocity impacts at different energy levels (5, 10 and 15 J). The damaged areas of the affected tubes were repaired with 2, 4 and 6 layers of glass/epoxy fabrics. The repaired tubes were then failed catastrophically by being subjected to monotonic internal burst tests based on ASTM D 1599-99 standards. Changes in the tubes' burst pressures were recorded and the resulting damages on the tubes were studied. It was found that, for all the energy levels employed in this study, a six-layered patch repairing is suitable for the retrofitting of impact damaged tubes. (C) 2014 Elsevier Ltd. All rights reserved.Öğe Virtual Testing of Laminated Composites Subjected to Low-Velocity Impact(Springer, 2023) Uyaner, Mesut; Kara, Memduh; Kepir, Yusuf; Gunoz, AlperComposite materials have many superior properties compared to traditional materials. However, due to its high cost, the composite structure must be designed correctly at the beginning. Composite structures are particularly sensitive to impact loads. Predicting the damages that will occur in the composite structure due to impact and designing accordingly will contribute significantly to the reduction of the negative situation caused by the high cost. In this study, the dynamic response of E-glass fiber-reinforced polymer (GFRP) laminated composites subjected to low-velocity impact was studied experimentally and numerically. Thus, it is aimed to determine the damage behavior with virtual tests before the composite structures are produced. Low-velocity impact tests were performed on composite samples that have different dimensions at impact velocities of 2.0, 2.5, and 3.0 m/s. Low-velocity impact tests were carried out by a vertical drop weight testing machine. A cylindrical impactor with a semispherical nose having a mass of 30 kg and a radius of 12 mm was utilized in the low-velocity impact tests. The impact was applied to the center of the composite laminates, the short sides of which are fixed. Numerical analyses were performed using the LS-DYNA finite element method package program with Tsai-Wu matrix failure criterion damage mechanics-based material model MAT 055. In addition, mesh optimization for the failure modeling parameters of the material model Mat_Enhanced_Composite_Damage (MAT 055) was realized. An agreement of up to 90% was observed between the numerical analysis and the experimental results. According to the results obtained from the experimental and numerical studies, it was seen that the size of composite plates significantly affects the impact behavior of the materials. In addition, it was observed that the ratio of the absorbed energy to the total energy increased and the damage to the samples increased with the increase of the impact energy.
