Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Mechanical Behavior and Modeling of Honeycomb Cored Laminated Fiber/Polymer Sandwich Structures(Izmir Institute of Technology, 2008) Sezgin, Fatma Erinç; Tanoğlu, Metin; Tanoğlu, Metin; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe use of composite sandwich structures is increasing in aerospace and civil infrastructure applications due to their high flexural and transverse stiffness and light weight. Considering different mechanical properties, sandwich structures can be manufactured from various core and facesheet materials.In this study, hand lay up technique was used for the fabrication of sandwich structures made of polypropylene based honeycomb core and glass fiber reinforced polymer (GFRP) facesheets. The non-crimp glass fibres and epoxy matrix were used for the production of GFRP laminates. The variation of the core thickness was the major parameter for considering the mechanical behaviour and failure mechanisms of the sandwich structures. Based on flatwise compression tests, an increase in compressive modulus and strength was observed with the increase of core thickness. For edgewise compression tests, peak loads up to crush of the sandwich panel was discussed by means of core thickness. According to the three point bending tests, a decrease in core shear stress and facesheet bending stress was observed as the core thickness increases.The modeling of sandwich structures were also carried out with three dimensional finite element models. The ANSYS 11 software was used for utilizing the test data in order to predict the mechanical behavior of the sandwich structures. In the finite element analysis, the test results of each constituent were employed as the input data for ANSYS. The experimental data and predicted results were found to be in good agreement in the elastic region, therefore the model can be used to predict the behavior of similar structures in elastic region.Master Thesis Inertial Effect in Aluminum Metal Foams(Izmir Institute of Technology, 2011) Kocatürk, Onur; Güden, Mustafa; Güden, Mustafa; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIn this study, Al tubes, Al foams of different types, Al sandwich plates of various configurations (orientations) and brittle glass foam samples were quasistatically reloaded in order to assess any micro inertia effect on the deformation stresses. Al foams tested quasi-statically were further reloaded (interrupted test) in Split Hopkinson Bar (SHPB) at dynamic strain rates in order to see effect of strain rate on micro inertia effect. Al empty tubes experienced micro inertia independent (Type I) deformation behavior in lateral compression and micro inertia dependent (Type II) deformation behavior in axial compression. The lack of strain rate sensitivity of the tested Alulight (AlSi10) closed cell Al foams (Al/Si) produced through powder route within the studied strain rate regime was attributed to the foam cell wall fracture during cell wall buckling. While Al foams with and without SiC addition showed micro inertia effect through progressive cell wall bending. In accord with these observations, Al and Al/SiC foams showed the strain rate sensitive, while Alulight foams showed strain rate insensitive plateau stress in the SHPB compression tests. The layer configuration/orientation was shown to affect Al sandwich plate deformation. Progressive bending of the interlayer fins resulted in strain rate depending crushing stress, while shearing of the interlayer resulted in strain rate insensitive deformation stress. As was expected, the strength enhancement was not seen in glass foam specimens tested as the cell walls were fractured under compressive loads. Finally, a simple testing method was shown to investigate micro inertia effect in hollow and cellular Al structures.