Optimization of SiO2 Nanoparticle concentration in Woven CFRP/Epoxy Composites for Hydrokinetic Turbine Blade Applications

Abstract Carbon fibre reinforced epoxy (CFRP/epoxy) laminates are promising candidates for hydrokinetic turbine blades owing to their high specific stiffness, strength, corrosion resistance, and design flexibility. This study systematically investigates the concentration-dependent influence of SiO₂ nanoparticles incorporated into the epoxy phase of a ten-ply plain-woven CFRP laminate at concentrations of 0–4 wt%. Six formulations (C0, C0.5, C1, C2, C3, and C4) were fabricated using ultrasonic nanoparticle dispersion followed by vacuum-assisted resin infusion. Physical characteristics, microstructural features, elemental composition, chemical structure, mechanical properties, thermo-mechanical behaviour, fatigue resistance, and representative blade-level structural response were evaluated. Tensile, flexural, and interlaminar shear properties were determined according to ASTM D3039/D3039M, ASTM D790, and ASTM D2344/D2344M, respectively, while SEM/EDS, FTIR, XRD, DMA, DSC, TGA, and coefficient of thermal expansion measurements were employed for comprehensive characterization. The optimum performance was obtained at 2 wt% SiO₂ (C2), with tensile strength, flexural strength, and interlaminar shear strength increasing from 612 to 674 MPa, 748 to 835 MPa, and 46.2 to 54.3 MPa, respectively. The DMA glass-transition temperature increased from 108.4 to 116.8°C, while storage modulus at 80°C increased from 34.5 to 42.8 GPa. The 5% mass-loss temperature increased from 342 to 353°C, and fatigue life at 0.65 UTS increased from 74,000 to 142,000 cycles. Higher nanoparticle concentrations diminished these improvements, attributed to particle clustering and matrix heterogeneity. Blade-level analysis further indicated reduced root-region stress and tip deflection for C2. Overall, 2 wt% SiO₂ provides a favourable material formulation for lightweight hydrokinetic turbine blade applications.