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Browsing by Author "Moura, Liane Raquel Neves"

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  • Development of high-performance epoxy- graphitic carbon nitride nanocomposites
    Publication . Moura, Liane Raquel Neves; Sadhu, Veera; Silva, Abílio Manuel Pereira da; Parente, João Miguel Nunes
    The introduction of nanofillers into epoxy resins is one of the numerous ways of reinforcing polymers. In accordance, this dissertation explores the synthesis, characterization, and performance optimization of epoxy-graphitic carbon nitride (GCN) nanocomposites, focusing on enhancing their mechanical and thermal properties. So, the research involves the preparation of epoxy-based nanocomposites through the incorporation of different concentrations of GCN nanoparticles into the epoxy resin, using common processing techniques, and subsequent analysis of their structural characteristics and properties. Besides that, this work aims to understand the influence of GCN loading and Polyhedral Oligomeric Silsesquioxane (POSS) particles on the nanocomposite's mechanical strength and thermal stability, aiming at aeronautical and aerospatial applications. The experimental results indicate that the most enhanced mechanical properties were observed for the nanocomposite reinforced with a concentration of 0.25 wt.% GCN. Consequently, this concentration was selected for the carbon fibre laminates, concluding that the addition of GCN resulted in an improvement of up to 81% in flexural strength (from 369.8 to 670 MPa) and up to 135% in flexural modulus (from 25.2 to 59.3 GPa), depending on the testing speeds. Increases of 25% in tensile strength (from 408.3 to 509.6 MPa) and 39% in elastic modulus (from 20.3 to 28.1 GPa) were also observed. As mentioned, the document also examines the influence of adding POSS particles to the carbon fibre laminates reinforced with GCN. Comparing the properties attained for the control sample with the ones obtained for the reinforced samples, it is possible to conclude that the incorporation of both nano reinforcements allows for improvements between up to 111% in flexural strength (from 369.8 to 781.2 MPa) and up to 117% in flexural modulus (from 25.2 to 54.7 GPa), for different testing speeds. In terms of tensile strength and elastic modulus, the increases were 30% (from 408.3 to 529.9 MPa) and 12% (from 20.3 to 22.7 GPa), respectively. The thermal properties of the laminates were also examined, through thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). It was found that the addition of nano reinforcements did not result in significant improvements in the glass transition and decomposition temperatures, although an improvement in the residual mass was observed in the laminates reinforced only with GCN. Finally, the hydrophobic properties of the two compositions and the control sample were evaluated, using water contact angle analysis (WCA). It was concluded that the presence of the reinforcements positively impacts these properties, with a more pronounced improvement in the sample reinforced only with GCN (from 73.6 to 82.5º).
    2024-11-25Master thesis Embargoed access Show more