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Öğe Buckling and compressive failure of stepped-lap joints repaired with composite patches(SAGE PUBLICATIONS LTD, 2012) Beylergil, Bertan; Aktas, Alaattin; Cunedioglu, YusufIn this study, the buckling and compressive failure of adhesively-bonded stepped-lap joints (with/without composite patches) composed of pultruded glass fiber-reinforced polymer composite laminates was investigated experimentally and numerically. Two-component epoxy adhesive was used for bonding purposes. Composite patches were woven glass-epoxy layer. They were added onto the conventional stepped-lap joints so that additional load transfer paths were created and localized stress concentrations near joint edge were reduced. The axial compression tests were performed and the results revealed that the buckling and failure load of new stepped lap composite joints with composite patches were significantly higher than the conventional stepped lap joints. The influence of the overlap length was evaluated. For both types of joints, a small increase was observed in failure loads by increase of the overlap length. Numerical results showed a very good agreement with experimental results.Öğe Enhancement of Single-Lap Composite Joints Strength at Different Temperatures(TAYLOR & FRANCIS LTD, 2012) Beylergil, Bertan; Cunedioglu, Yusuf; Aktas, AlaattinIn this study a novel reinforcing method was examined for glass-fiber reinforced composites consisted of inter-adherend glass fibers which acted as pins to pierce the composite adherend. Two types of inter-adherends were investigated. One of the types involved fibers which acted as pins (type B), and the other type was made up of pin like fibers with bent edges which stuck to the surface of the adherend (type C). Static tensile tests were performed on both types of single-lap joints (SLJ) and for joints without inter-adherend fibers (type A) at four different temperatures (20, 40, 60 and 80 degrees C) in accordance with ASTM standards. The results showed that the fibers improved the ultimate static strength of the single-lap joints over the entire temperature range. (C) Koninklijke Brill NV, Leiden, 2012Öğe Experimental and numerical analysis of single lap composite joints with inter-adherend fibers(ELSEVIER SCI LTD, 2011) Beylergil, Bertan; Cunedioglu, Yusuf; Aktas, AlaattinIn this study, a novel reinforcing method for glass-fiber reinforced composites, which consists of inter-adherend glass fibers (IAF) that get through the composite adherend like a pin, was investigated experimentally and numerically. Two types of joints were investigated. One is the traditional single lap joint without inter-adherend (Type A) and the other is Type B in which the fiber pin was used. Static tensile tests were performed at ambient environment in accordance with ASTM standards. In the numerical analysis, ANSYS 12.0 software package was used. The results show that the fibers improve the ultimate strength and damage tolerance of composite joints. In addition, the numerical results show a good agreement with the experimental ones. (C) 2011 Elsevier Ltd. All rights reserved.Öğe Free vibration analysis of damaged composite beams(TECHNO-PRESS, 2015) Cunedioglu, Yusuf; Beylergil, BertanIn this study, free vibration analyses of symmetric laminated cantilever and simply supported damaged composite beams are investigated by using finite element method (FEM). Free vibration responses of damaged beams are examined using Euler Bernoulli beam and classical lamination theories. A computer code is developed by using MATLAB software to determine the natural frequencies of a damaged beam. The local damage zone is assumed to be on the surface lamina of the beam by broken fibers after impact. The damaged zone is modeled as a unidirectional discontinuous lamina with 0 degrees orientations in this study. Fiber volume fraction (v(f)), fiber aspect ratio (L-f/d(f)), damage length (L-D) and its location (lambda/L), fiber orientation and stacking sequence parameters effects on natural frequencies are investigated. These parameters are affected the natural frequency values significantly.Öğe Free vibration analysis of laminated composite beam under room and high temperatures(TECHNO-PRESS, 2014) Cunedioglu, Yusuf; Beylergil, BertanThe aim of this study is to investigate the effects of the beam aspect ratio(L/h), hole diameter, hole location and stacking layer sequence ([0/45/-45/90](s), [45/0/-45/90](s) and [90/45/-45/0](s)) on natural frequencies of glass/epoxy perforated beams under room and high (40, 60, 80, and 100 degrees C) temperatures for the common clamped-free boundary conditions (cantilever beam). The first three out of plane bending free vibration of symmetric laminated beams is studied by Timoshenko's first order shear deformation theory. For the numerical analyses, ANSYS 13.0 software package is utilized. The results show that the hole diameter, stacking layer sequence and hole location have important effect especially on the second and third mode natural frequency values for the short beams and the high temperatures affects the natural frequency values significantly. The results are presented in tabular and graphical form.Öğe In view of sustainable future energetic-exergetic and economic analysis of a natural gas cogeneration plant(INDERSCIENCE ENTERPRISES LTD, 2013) Gungor, Afsin; Bayrak, Mustafa; Beylergil, BertanThermodynamics plays an important role in performing energy and exergy analyses of industrial processes. The first law is widely used in engineering practice, and is the basis of the heat-balance method of analysis that is commonly used in energy systems performance analysis. However, the second law involves the reversibility or irreversibility of processes, and is a very important aspect of the exergy method of energy systems analysis. For a sustainable future, exergy analysis allows for improvements not necessarily attainable via energy methods, like increased efficiency, reduced fuel use and reduced environmental emissions. From the viewpoints of energy conservation and environmental benefits, cogeneration systems can be considered as systems of sustainable energies. From this point of view, in this study, the energy, exergy and economic analysis of an actual natural gas cogeneration plant with a total capacity of 121.5 MWh electrical powers is carried out. The first and second law efficiency of the cogeneration plant is calculated as 40.8% and 90.2%, respectively. The pay-back period of the cogeneration plant is calculated as three years, which means this plant runs quite efficiency and economically.Öğe Poliamid 6/6 (PA 66) mikrofiberler ile toklaştırılmış tabakalı kompozitlerin mod-I delaminasyon direncinin istatiksel analizi(Niğde Ömer Halisdemir Üniversitesi, 2019) Beylergil, Bertan; Tanoğlu, Metin; Aktaş, EnginFiber takviyeli kompozitler, ağırlıklarına oranla yüksek mukavemet ve rijitlikleri nedeniyle uzay ve otomotiv yapısal parçalarında yaygın olarak kullanılmaktadır. Delaminasyon, bu kompozitlerde görülen en yaygın ve kritik hasar modudur. Bu kompozitlerin delaminasyon direncini arttırmak amacıyla, nanokatkılar ile epoksi toklaştırması, dikişleme, z-pimler ve arayüzeyde mikro/nanofiber kullanılması gibi pek çok sayıda teknik geliştirilmiştir. Bu çalışmada, poliamid 6/6 (PA 66) mikrofiberler ile toklaştırılmış karbon fiber/epoksi kompozitlerin Mode-I delaminasyon direnci Weibull dağılımı kullanılarak istatiksel olarak analiz edilmiştir. Test verilerinin istatiksel olarak değerlendirilmesi sonucunda PA 66 mikrofiberlerin kullanılmasının %90 güven seviyesinde kırılma tokluğunu yaklaşık %445 mertebesinde arttırdığı gözlemlenmiştir.Öğe Yapıştırılarak bağlantı sağlanan kompozit plakaların bağlantı performansının arttırılması(Niğde Üniversitesi, 2010) Beylergil, Bertan; Aktaş, Alaattin; Cunedioğlu, YusufMalzemeler; cıvata, perçin, kaynak, lehimleme, yapıştırma gibi değişik metotlar kullanılarak birleştirilebilmektedir. Bu metotlardan yapıştırma bağlantılarının günümüz endüstrisinde kullanımı hızla artmaktadır. Yapıştırma bağlantıları ile birleştirmelerde hafiflik sağlanmakta, farklı özelliklerdeki ve kalınlıklardaki malzemeler birleştirilebilmekte, düzgün bir gerilme dağılımı elde edilebilmekte ve daha ekonomik birleşimler meydana getirilebilmektedir. Bu avantajları nedeniyle yapıştırma bağlantıları diğer mekanik birleştirme yöntemlerine alternatif olarak kullanılmaya başlamıştır. Bu çalışmada, tek tesirli kompozit/ kompozit yapıştırma bağlantılarının mukavemetini iyileştirmek amacıyla Aktaş ve Polat [86] tarafından çalışılan bağlantı türleri (B ve C tipi) farklı sıcaklıklar altında deneysel ve nümerik olarak incelenmiştir. Statik çekme deneyleri dört farklı sıcaklıkta(20, 40, 60, 800C) gerçekleştirilmiş ve nümerik çalışmada Ansys 11.0 yazılımı kullanılmıştır. Nümerik ve deneysel çalışmalar sonucunda, B ve C tipi bağlantıların, oda sıcaklığında geleneksel A tipi bağlantı sistemlerine göre bağlantı mukavemetinde sırasıyla %80.7 ve %127'lik bir iyileştirme sağladığı ve buna ek olarak, yöntemin yüksek sıcaklıklarda da bağlantının mekanik performansını iyileştirdiği görülmüştür.
