Design and development of electromagnetic wave absorbing composites effective at microwave frequencies /

Hamat, Özgür
In the scope of this study, EM wave absorbing composites effective at microwave frequencies having crucial properties for their structural applicability will be designed and developed making use of a novel approach originating from our research group. For this purpose, surfaces of glass and polymeric fiber woven fabrics were modified via metal coatings with nm order thickness, where EM wave absorbing structural composites were formed by incorporating multilayered combinations of these surface-modified woven fabrics within polymer matrices. EM wave reflection and transmission properties, and hence absorption characteristics of surface-modified single layer and multilayer fiber woven fabrics were investigated using Free-Space test method. Based on the experimental data achieved on single layer woven fabrics, simulation studies were conducted in order to predict the EM wave absorption characteristics of multilayered reinforcement structures. In the last phase of the study, structural prototype EM wave absorbing polymer matrix composite is produced by placing surface modified multilayer fiber woven reinforcement materials with the highest EM wave absorption. More than 90% EM wave absorption was achieved with the fabricated composites in 18-40 GHz frequency range. Critical design principles required to reach to this challenging target were presented using simulations and experimental studies.


Design and implementation of magnetic field sensors for biomedical applications /
İnan, Ulaş Can; Gençer, Nevzat Güneri; Department of Electrical and Electronics Engineering (2015)
In this work, firstly the magnetic sensor types and their feasibility for biomedical applications are investigated. Then the air-cored induction coil sensor is chosen due to its advantages. Afterwards the usage of induction coils combined with amplifiers and connection types are studied. The biomedical applications requiring the use of magnetic field sensors are introduced. One of them, Lorentz Field Electrical Impedance Tomography (LFEIT) is explained in detail and experimental work is done for this applic...
Design and Optimization of Nanoantennas for Nano-Optical Applications
Işıklar, Göktuğ; Ergül, Özgür Salih; Department of Electrical and Electronics Engineering (2020-9)
In this study, design and simulation of plasmonic nanoantenna structures to obtain high power enhancement capabilities at optical frequencies, as well as utilization of nanoantennas for imaging and sensing applications are presented. Plasmonic characteristics of nanoantennas, which depend on many parameters, such as material, frequency, geometry, and size, are investigated in detail via computational analyses of various nanoantenna structures. Numerical solutions of electromagnetic problems are performe...
Cetin, Ramazan; Erturk, Ozan; Akın, Tayfun (2018-09-14)
This study presents design, analysis, optimization, and fabrication of umbrella structures as an efficient quarter wave absorber within the Long Wave Infrared (LWIR) range for uncooled IR detectors. Both the effect of the ni-chrome (NiCr) layer and effect of varying pixel pitch sizes on the IR absorption performance of the umbrella structures are examined. An average of 96% absorption is measured for the optimized case within the LWIR range.
Investigation of rough surface scattering of electromagnetic waves using finite element method
Aşırım, Özüm Emre; Kuzuoğlu, Mustafa; Özgün, Özlem; Department of Electrical and Electronics Engineering (2013)
This thesis analyzes the problem of electromagnetic wave scattering from rough surfaces using finite element method. Concepts like mesh generation and random rough surface generation will be discussed firstly. Then the fundamental concepts of the finite element method which are the functional form of a given partial differential equation, implementation of the element coefficient matrices, and the assemblage of elements will be discussed in detail. The rough surface and the overall mesh geometry will be imp...
A study on the effects of gamma radiation on the properties of polycarbonate
Kinalır, Kerim Gökhan; Usanmaz, Ali; Kaynak, Cevdet; Department of Polymer Science and Technology (2011)
This thesis aims to investigate the effects of gamma radiation on the properties of polycarbonate, an engineering thermoplastic which has a wide range of applications. A commercial grade polycarbonate resin, after being shaped into the required specimen forms by injection molding, was irradiated with different doses up to 180 kGy. Tensile strength was found to decrease with increasing dose. The lowest values of tensile modulus, flexural modulus and flexural strength were obtained at 96 kGy, which is also th...
Citation Formats
Ö. Hamat, “Design and development of electromagnetic wave absorbing composites effective at microwave frequencies /,” M.S. - Master of Science, Middle East Technical University, 2014.