Master Degree / Yüksek Lisans Tezleri

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Department: search.filters.department.Thesis (Master)--İzmir Institute of Technology, Materials Science and EngineeringSubject: search.filters.subject.Fibrous composites

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Now showing 1 - 3 of 3
  • Master Thesis
    Joining and Interfacial Properties of Aluminum/Glass Fiber Reinforced Polypropylene Sandwich Composites
    (Izmir Institute of Technology, 2009) Guruşçu, Aslı; Tanoğlu, Metin; Tanoğlu, Metin; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The joining of separate components using a suitable technique is a critical step in the manufacture of composite structures. For good property performance of aluminum/glass fiber reinforced polypropylene (Al/GFPP) laminates, one of the most important problems is to obtain good adhesive bond strength.In the present study, Al/GFPP laminates have been manufactured with various surface pretreatment techniques. Adhesion at the composite/metal interface has been achieved by surface pretreatment of Al with amino based silane coupling agent, incorporation of polyolefin based adhesive film and modification with PP based film containing 20 wt. % a maleic anhydride modified polypropylene (PP-g-MA). The mechanical properties shear, peel and bending strength of the adhesively bonded Al/GFPP laminates were investigated to evaluate the effects of those various surface treatments. In addition, peel strengths of Al foam/GFPP laminates with various surface treatments were measured. The fracture surfaces have been examined by scanning electron microscope (SEM). Results showed that the adhesion of the laminated Al/GFPP systems were improved by treatment of aluminum surfaces with amino-based silane coupling agent. Based on peel and bending strength results, Al/GFPP laminates with incorporation of polyolefin based adhesive films exhibited significant increase on the adhesive behaviour. Modification of Al/GFPP interfaces with PP-g-MA layer leads to highest improvement on the adhesion properties.
  • Master Thesis
    Quasi-Static and High Strain-Rate Mechanical Behavior of Fp™ (α-Alumina) Long Fiber Reinforced Magnesium and Aluminum Metal Matrix Composites
    (Izmir Institute of Technology, 2004) Akil, Övünç; Güden, Mustafa; Güden, Mustafa; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The mechanical response of an FP long fiber (35%) Mg composite has been determined in the transverse and longitudinal directions in compression. Results were also compared with those of a similar composite of Al matrix. It was found that the composite in the transverse direction exhibited strain rate sensitivity of the flow stress and maximum stress within the studied strain rate range (10-4 to 1x103s-1). However the increase in strain rate decreased the failure strain. Microscopic observations on the failed samples have shown that the composite failed predominantly by shear banding. Near to the fracture surface DRX grains were observed within the shear band and it was proposedthat the lower ductility of the composite at increasing strain rates was due to the early DRX grain formation which softened thecomposite and resulted in lower ductility. Although twinning was observed in the deformed cross-sections of the samples at all strain rates particularly near the shear band region, it was proposed that the main deformation mechanism was slip which was evidenced by the slip lines on the fracture surface. The strain rate sensitivity in fracture stress of the composite in transverse direction was also found to be similar to that of the Al composite tested in the same direction. In the longitudinal direction, the composite failed by kink formation at quasi-static strain rates, while kinking and splitting at high strain rates. The maximum stress in the axial direction was however foundto be strain rate insensitive. In this direction similar to transverse direction DRXgrain formation was observed in the kink region. The lack of strain rate sensitivity in this direction was attributed to DRX grain formation at high strain rates combined with adiabatic heating and the brittle nature of the composite leading to fluctuatitonin the compressive strength.
  • Master Thesis
    Effects of Processing Parameters on the Mechanical Behavior of Continuous Glass Fiber/Polypropylene Composites
    (Izmir Institute of Technology, 2009) Merter, Nevres Emrah; Tanoğlu, Metin; Tanoğlu, Metin; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Fiber reinforced polymeric composite materials have an increasing demand in industrial applications. Easy and rapid processing capability, high impact and delamination resistance, low moisture absorption and infinite shelf life of the raw materials are the attractive properties of continuous fiber reinforced thermoplastic composite materials. Therefore, thermoplastic based composites find in many application areas in automobile, aerospace, construction, defense, transportation and marine industries. In recent years, hybrid fabrics; composed of continuous glass fibers and polymer fibers such as polypropylene (PP), have been used to fabricate thermoplastic composite with higher fiber volume fraction and improved performance. In this study, hybrid fabrics were developed by commingling the continuous PP and glass fibers using air jet and direct twist hybrid yarn preparation techniques. The hybrid commingled fabrics obtained with 450 fiber orientation and non-crimp fabric pattern. Non-crimp fabrics were obtained various fiber sizing that are compatible and incompatible with PP matrix to investigate the effect of interfacial adhesion on the properties of the thermoplastic composites. Composite panels were produced from these fabrics via hot press compression method. Microstructural properties of the composites were investigated by matrix burn-out test and optical and scanning electron microscopy (SEM) analyzes. Tensile, compression, flexural and interlaminar peel tests were used to investigate the mechanical properties of the composites. Impact properties of the composites were examined by charpy impact test. Results showed that laminates of the fabrics fabricated by air jet hybrid yarn preparation technique exhibit superior properties to those fabricated by direct twist covering hybrid yarn preparation technique. The results also showed that the fabrics with polypropylene compatible sizing results with enhanced composite properties.