Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Development of Joining Techniques for Carbon Fiber Based Polymer Matrix Composites(Izmir Institute of Technology, 2020) Tanoğlu, Metin; Tanoğlu, Metin; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIn recent years, adhesive bonding has been a promising joining technology for CFRP composites. An appropriate treatment of surfaces for adhesive bonding is one of the effective factors for obtaining a high-quality adhesion strength. However, the adhesion strength is decreased by contaminants, like release agents, as well as an excess of matrix in the top layer. The contact of the adhesive with the reinforcing element is critical. Therefore, it is necessary to make a pre-preparation process on the adherent surface. One of the surface treatments preferred due to the advantages it provides is laser processing. The joint area strength of CFRP (carbon fiber reinforced polymer) composite can be enhanced with laser surface treatment. In this work, the carbon fiber/epoxy composites surface treatment by a nanosecond (1064nm wavelength) laser has been investigated. The polymer layer (epoxy matrix) on the CFRP (carbon fiber reinforced polymer) composite surface was selectively removed by laser treatment to expose carbon fibers. In order to remove the epoxy from the surface sufficiently, laser surface modification parameters were investigated and their effects were examined. These parameters are laser power, frequency, scanning speed and offset distance, respectively. Epoxy removal and fibers damage was analyzed by optical microscope and SEM (scanning electron microscope). Contact angle tests were carried out to analyzed wettability effect on the laser parameters. Lap shear, charpy impact and double cantilever beam (DCB) tests were performed to examine the effect of laser surface modification on mechanical performance.Master Thesis Investigation of Environmental Durability of Carbon Fiber/Epoxy Composites(Izmir Institute of Technology, 2013) Yağmur, Samet; Tanoğlu, Metin; Tanoğlu, Metin; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyFiber reinforced polymer composites, that have increasing demand in many applications such as aircraft and automotive industry, are usually exposed to different environmental conditions which may be harmful to them. The investigation of their environmental durability is critical for those applications. The objective of this study was to investigate the effects of temperature and moisture on durability of carbon fiber reinforced epoxy composites. For this purpose, 0/90° woven, plain unidirectional and non-crimp biaxial ±45 fabrics were used as reinforcement. The specimens were manufactured using vacuum resin infusion process to obtain relatively high fibre volume fraction ratios. The composites manufactured were exposed to cyclic aging conditions to simulate aircraft flight environment. Hygrothermal, high temperature and freezing conditions were used as in one cycle which was 12 hours long. Moisture absorption was determined by weighing the specimens at regular intervals as a function of aging cycles. Tensile and flexural tests were performed prior to aging and after 500, 1000 and 1500 hours aging. After the completion of aging cycles, the moisture content did not increase significantly due to presence of subzero and high temperatures in aging cycles. The mechanical test results revealed differences based on the fabric types used. It was found that the tensile strength and modulus values of woven composites increased after aging cycles as compared to those of unidirectional and biaxial composites. On the other hand, flexural properties decreased at the end of the aging cycles for the composites aged as test coupons.