Mechanical and Thermal Properties of Basalt Fiber/Nano-Silica-Reinforced Epoxy Composites

This study investigates the development and characterization of high-performance epoxy-based composites reinforced with basalt fibers and nano-silica. Five formulations were evaluated, including neat epoxy and basalt fiber-reinforced composites with varying nano-silica contents. The developed materials were characterized in terms of tensile strength, Young’s modulus, elongation at break, flexural strength, impact resistance, hardness, density, water absorption, thermal conductivity, and char yield, using applicable ASTM standards. The results indicate that basalt fiber reinforcement improves the mechanical properties of the epoxy matrix, while nano-silica provides additional benefits through enhanced stress transfer, potential restriction of polymer-chain mobility, nanovoid filling, and modification of crack propagation. Among the investigated formulations, the composite containing 20 wt.% basalt fibers and 2 wt.% nano-silica exhibited the best overall performance. It achieved tensile and flexural strengths of 119.6 MPa and 166.8 MPa, respectively, and an impact strength of 35.7 kJ/m². The composite also demonstrated a seven-day water absorption of 0.81%, a glass transition temperature of 94 °C, and a temperature of 338 °C at 5% mass loss. Increasing the nano-silica content to 3 wt.% resulted in a slight reduction in several properties, potentially owing to particle agglomeration, increased resin viscosity, and reduced dispersion efficiency. These findings suggest that optimizing the proportions of basalt fibers and nano-silica can improve the mechanical performance, moisture resistance, and thermal stability of epoxy-based composites, supporting their potential use in structural and general engineering applications.