Multi scalable design and performance characterization of glass fiber reinforced epoxy composites by ıncorporation of hexagonal boron nitride in resin and on ınterfaces

Official URL: https://risc01.sabanciuniv.edu/record=b2771006_(Table of contents)

Thermal conductive materials are widely utilized to efficiently dissipate energy especially in the heat-generated electronic systems in aerospace systems. Polymeric materials are selected as structural materials due to their high chemical resistance, mechanical strength, and lightweight; on the other hand, their usage is restricted by their low thermal conductive nature. The particulate filler reinforcements are a promising way to enhance the thermal conductivity of the polymers since these fillers also improve the mechanical properties and preserve the structural consistency of polymers. In this thesis, epoxy is one of the most common thermoset polymers, and the incorporation of micron- and nano-sized hexagonal boron nitride (h-BN) particles in comprehensive weight percentages were performed to evaluate the effect of particle size and loading ratio on thermal conductivity enhancement of epoxy. Firstly, the micron-sized h-BN particles were integrated homogeneously into epoxy to evaluate the effect of the concentration of the h- v BN particles on the thermal and mechanical performance of the epoxy by sonication. The thermal performance of the epoxy showed significant enhancement by increasing the concentration of the h-BN particles up to 20 wt%, and the in-plane and through-thickness thermal conductivities of h-BN integrated reinforced epoxy composites improved by 107% and 112%, respectively. On the other hand, the mechanical properties exhibited an upward trend until they reached optimum concentration level, whereby tensile and flexural modulus were improved by 46.9% and 40.6% with the loading h-BN ratios of 20 wt% and 10 wt%, respectively. As a second parameter, the particle size was investigated to determine its effect on the thermal and mechanical properties by incorporation of the nano-sized h-BN in epoxy with the same loading levels. The thermal conductivity performance of the epoxy reached the highest value for 20 wt% h-BN particles with 40.5% and 35.1% enhancement levels in in-plane and through-thickness directions less than the micron-sized h-BN particles reinforced epoxy. In addition, the highest tensile and flexural modulus enhancements were achieved by 16% and 15% by incorporating 20 wt% nano-sized h-BN particles. In the second part of the study, the 10 wt% h-BN particles were integrated into neat and SWCNT coated glass fiber reinforced epoxy composites to enhance the thermal performance of the composites by vacuum infusion method, and a 32% improvement was obtained for the hybrid fabric design having neat and nano-coated fabrics together. In conclusion, the incorporation of h-BN particles with large particle sizes is an efficient way to improve the thermal performance of composite materials due to the construction of thick and stable thermal conductive pathways and the limitation of interfacial phonon scattering areas. The investigation of the particle size-concentration relationship of particulate reinforcements allows new insight in polymer matrix composites to control the thermal management in the structural application and will be a guideway for the development of new designs and multifunctional and multi-scale composites with tailored functionalities.