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Performance of the nanosilica filled neat epoxy and carbon fiber filament wound composites

2019
Sapancı, Erdal
The main aim of this thesis was to investigate influences of nanosilica particle addition to epoxy resin matrices (systems) on the thermal and mechanical properties of carbon fiber reinforced epoxy-nanosilica composites. Nanosilica particles were used for increasing the matrix dependant mechanical properties of conventional composite materials with easy dispersion processes in matrix. In the first part of the thesis, nanosilica filled epoxy composites were prepared using both a probe type ultrasonic processor and manuel mixing. Viscosities of the nanosilica filled epoxy resins were determined to understand the gelling time and wetting behaviour of those resins and to select the processing parameters for the filament winding process. The nanosilica filled epoxy composites with different weight ratios of nanosilicas were prepared, and then the mechanical, thermal, and morphological characterizations of the cured specimens were carried out. The best result in terms of tensile strength for those composites was obtained when 0.5 wt% nanosilica was added. The addition of nanosilica did not influence the elastic modulus of those composites considerably. In the second part of the thesis, the aim was to investigate the effects of nanosilica on the properties of carbon fiber reinforced epoxy composites. Test coupons for mechanical tests were prepared from the flat plates manufactured using a filament winding process. The glass transition temperatures of the nanosilica filled carbon fiber reinforced epoxy composites were measured using a Dynamic Mechanical Analyser (DMA). The addition of silica particles did not change the glass transition temperatures of the composites. The Scanning Electron Microscope (SEM) analyses were performed to understand damage mechanisms of the nanosilica filled carbon fiber reinforced epoxy composites. Mode I interlaminar fracture toughness energy, GIC, of the nanosilica filled carbon fiber reinforced epoxy composite containing 2.0 wt% nanosilica was increased 104% compared to the control sample (i.e. no nanosilica added sample). Mode II interlaminar fracture toughness energy, GIIC, of the carbon fiber reinforced containing 0.5 wt% nanosilica was increased about 21% compared to the control sample. The tensile strength of the carbon reinforced composites were increased 13.5% increase with addition of 0.5 wt% nanosilica in epoxy.