Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Improving Mechanical Properties of Adhesive Joints in Carbon Fiber Reinforced Polymer Composites by Incorporation of Graphene Added Electrospun Polymeric Nanofibers(01. Izmir Institute of Technology, 2023) Yeke, Melisa; Tanoğlu, MetinSince composites joined with mechanical fasteners cause severe delamination damage, stress concentration in the joint area, and weight increase, joining composite materials with innovative methods have recently gained more importance. These joining methods prevent delamination damage, provide a uniform distribution of stress, and do not cause considerable weight increases. However, modifying the surface of composite parts joined by innovative methods is critical. In this study, the bonding surface was modified by coating carbon/epoxy prepregs with electrospun nanofibers with 10% wt/v ratio of PA 66 and 1%, 2% and 3% wt/v ratio of rGO added. Composite parts were joined in the hot press by the secondary bonding method using 3 plies of FM 300K film adhesive. The morphological structure of nanofibers and the dispersion of rGO were analyzed by SEM. The thermal properties of nanofibers were analyzed by DSC. The contact angle measurement device was used to determine the hydrophilic and hydrophobic properties of the unmodified prepreg and nanofiber-modified prepreg surface. The most hydrophilic surface was observed on the nanofiber-coated surface with 2% rGO added. Single Lap Joints (SLJ), and Charpy Impact tests were performed to examine the mechanical properties of modified and unmodified composite plates. According to the SLJ and Charpy Impact results, an improvement of 17.89% and 30.59% was observed in carbon/epoxy composite plates whose surface was modified with 2% rGO, respectively.Master Thesis Improving Joining Performance of Composites by Electro-Spinning of Nano Fibers(01. Izmir Institute of Technology, 2021) Esenoğlu, Gözde; Tanoğlu, MetinMechanical joints traditionally used in composite materials (screws, rivets, etc.) not only increase weight but also act as a stress collector, causing serious delamination problems. At the same time, the development of alternative joining techniques has become an important issue in the composite industry due to its sensitivity to corrosion, electromagnetic properties/radar absorption properties, labor cost and adverse effects on the manufacturing process. In this master's thesis, the effects on the mechanical properties of two different prepreg composites (UD and woven) coated with polyamide 66 (PA 66) nanofibers in the joint region were investigated. In addition, the fiber structures of the produced PA66 nanofibers were investigated. The produced nanofibers were directly coated on the bond zone layer (top surface) of the carbon prepregs. The reference and nanofiber doped prepregs were cured by the hot press method, and then they were combined with the secondary bonding method using FM300K film adhesive in the hot press. Tensile, compression, bending, shear, Charpy-impact and double cantilever beam (DCB) tests were performed on the produced samples. The effect of homogeneity and areal weight density (AWD) of PA66 nanofibers on mechanical performance was investigated. The morphology and post-test deformations of the nanofibers were investigated by scanning electron microscopy (SEM). The thermal properties of PA66 nanofibers were investigated by the differential scanning calorimetry (DSC) method. By comparing the SEM images and the lap shear test results, the most efficient parameters for the mechanical performance of the composites were determined. The results showed that PA66 nanofibers produced with a 10% wt solution ratio and 10 min coating time were the most efficient on composites. The addition of PA66 nanofibers to the junction region with the electro-spinning technique has been proven to increase the junction region performance of the materials and outputs have been obtained.