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    A Comparative Study on the Effect of CNT or Alumina Nanoparticles on the Tensile Properties of Epoxy Nanocomposites
    (SPRINGER HEIDELBERG, 2019) Yazman, Sakir; Samanci, Ahmet
    In this paper, the mechanical properties of the carbon nanotube (CNT) or alumina (Al2O3) nanoparticles (NPs)-modified epoxy composites were investigated experimentally. Composite dog-bone tensile specimens were prepared and tested according to ASTM D638-14 standards with CNT or Al2O3 nanoparticle contents of neat, 0.5, 0.75, 1.0, 1.25, 1.5, 1.75 and 2.0% of the total resin weight. In order to compare the effect of nanoparticle type and content on the mechanical properties, tensile stress-strain curves were drawn for each parameter. Also, the ultimate tensile strength (UTS), Young's modulus and toughness values were obtained and compared. Considerable improvements of the mechanical properties were observed by adding NPs. The results indicated that the UTS, Young's modulus, and toughness values reached a maximum with an increment of 27.6, 18.7 and 187.9%, respectively, at Al2O3 nanoparticle content of 1.0wt%, according to neat epoxy. Due to lower cost and good mechanical properties of the Al2O3 nanoparticle-modified composites, the Al2O3 nanoparticle can be used as a reinforced particle for epoxy composites. On the other hand, it was observed that the CNTs were not as effective as Al2O3 nanoparticles.
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    Fatigue crack growth of filament wound GRP pipes with a surface crack under cyclic internal pressure
    (SPRINGER, 2008) Samanci, Ahmet; Avci, Ahmet; Tarakcioglu, Necmettin; Sahin, Oemer Sinan
    In this study, fatigue damage behavior of (+/-75(3)) filament wound composite pipes with a surface crack under alternating internal pressure was investigated. The specimens were tested at room temperature and exposed to open ended fatigue tests in which the pipe can be deformed freely in the axial direction. The tests were carried out in accordance with the ASTMD-2992 standard. The alternating internal pressure was generated by conventional hydraulic oil. The low cycle tests were performed with 0.42 Hz frequency and R = 0.05 stress ratio. Glass reinforced polymer pipes (GRP) are made of E-glass/epoxy and have (+/-75(3)) configuration. Surface cracks were machined in the axial direction of the pipes which have depth-to-thickness ratios a/t = 0.25-0.38-0.50 and depth to length ratio of a/c = 0.2. Tests were performed at three different loads of 50%, 40%, and 30% of ultimate hoop stress strength of unnotched pipes. The failure behavior of GRP pipes during the test was observed and fatigue test results were presented by means of (S-N) Curves and delamination damage zone area-cycle (A-N) curves.