Influence of Bio-extracted Thespesia populnea Fiber and Waste-derived CaO Nanoparticles on the Mechanical and Thermal Properties of Epoxy Composites

Bio composite materials had gained significant attention in recent years because of their sustainability, lightweight nature, and favorable strength-to-weight characteristics. In the present study, epoxy-based composites reinforced with bio-extracted Thespesia populnea fiber and tuber waste-derived calcium oxide nanoparticles were developed using hand layup technique. The fabricated composites were evaluated for their mechanical and thermal performance in accordance with ASTM standards. Among the developed samples, the ETC2 composite containing 40 vol.% fiber and 4 vol.% CaO nanoparticles, exhibited superior mechanical properties with tensile, flexural, compressive and impact strengths of 139 MPa, 166 MPa, 151 MPa, and 6.5 J, respectively. The enhanced performance is attributed to improved efficient stress transfer and interfacial bonding among matrix, fiber and nanoparticles. Furthermore, ETC3 composite (6 vol.% CaO) showed the highest thermal stability with decomposition temperature of 382 ℃ and the lowest thermal conductivity of 0.26 W/m-1K-1, indicating its excellent thermal insulation capability. The progressive improvement in thermal behavior with increasing CaO content is associated with enhanced phonon scattering, increased interfacial thermal resistance, and disruption of heat conduction pathways within the matrix. Morphological analysis using scanning electron microscopy confirmed improved filler–matrix interaction and dispersion characteristics, which directly influenced the mechanical and thermal performance of the composites. The developed biocomposites exhibit strong potential for applications in automotive, aerospace, defense, sports, and thermal insulation systems.