Thermo-Mechanical and Flame-Retardant Performance of Epoxy/Hemp Composites Reinforced with Nano-SiO2 and Al(OH)3

With increasing ecological concerns and the demand for biodegradable materials, natural fiber-reinforced polymer composites have been recognized as a promising replacement for synthetic materials, particularly in thermal and fire-resistant deployment. The primary objective of the current research is to evaluate the mechanical, thermal, and fire-retardant properties of epoxy/hemp composites with the inclusion of different weight proportions (3, 6, and 9 wt.%) of nanofillers like silicon dioxide (SiO₂) and aluminum trihydrate (Al(OH)₃). The composites were fabricated through the conventional hand layup method. Before fabrication, the hemp fibers were pretreated with hydrogen peroxide (H₂O₂) solutions to increase the adhesion between fibers and matrix. The results revealed that among the tested nanofiller concentrations, 6 wt.% of nanofillers significantly enhanced the mechanical properties like tensile (59.84 MPa for Al(OH)₃ and 66.14 MPa for SiO₂) and flexural (21.74 MPa for Al(OH)₃ and 18.74 MPa for SiO₂). The included nanofillers exhibit better OH⁻ interaction with hemp fibers, which helps to enhance the mechanical properties of hybrid composites. It was confirmed through FTIR and XRD analysis. According to the results of cone calorimetry, the incorporation of Al(OH)₃ and SiO₂ nanofillers reduces the peak heat release rates by up to 16.21%. It may happen due to the development of dense char layers and the release of water vapor between 300 and 400 °C via endothermal action. This mechanism helps to increase the flammability characteristics of epoxy/hemp-based hybrid composites. These enhanced epoxy/hemp-based hybrid nanocomposites are suitable for automotive, aerospace, electrical enclosures, and construction-based sectors.