DEVELOPMENT OF SYNTACTIC FOAMS WITH LOW DENSITY, HIGH SPECIFIC COMPRESSION STRENGTH AND RF TRANSPARENT

This study aims to develop a unique manufacturing process that allows to reach volume fraction of hollow glass microballoons (HGM) up to %80 and enable to use of different thermoset resins such as epoxy, silicone and cyanate ester for syntactic foams. Thus, syntactic foams with different types of resin can be produced at the desired HGM concentrations. Another purpose of this work is to produce syntactic foams in complex geometries (by means of a mold) whereas the companies in the industry can only produce syntactic foams in the form of planar plates. With this manufacturing process, the requirements of many applications (such as buoyancy, aerospace, submarine, antenna, radome etc.) can be satisfied.

The effect of HGM content and resin type on physical, mechanical, thermal and electrical properties has been studied for syntactic foams. Syntactic foams were characterized by using Scanning Electron Microscopy (SEM) to analyze their structural morphology and to ensure their homogeneity. The characterizations continued with theoretical and experimental density measurements, finding void amount in syntactic foams and tensile-compression tests. It was observed that the compression and tensile strength decreased with increasing HGM concentrations. In compression and tensile tests, the failure of syntactic foam was different from each other and degradation of the syntactic foams varied according to the resin type. The free space measurement method is used to find the electrical properties of syntactic foams. To observe viscous behavior and glass transition temperature (T_g) of syntactic foams, dynamic mechanical analysis (DMA) was conducted. Lastly, to determine heat capacity rate (c_p) and thermal conductivity (, differential scanning calorimetry (DSC) and HOT DISK tests were conducted for syntactic foams respectively. With density, specific heat and thermal conductivity values, thermal diffusivity and thermal effusivity values of syntactic foams were also presented.