Influence of Ramie Fibre Surface Treatment on the Mechanical and Interfacial Performance of Woven Ramie Carbon–Kevlar Hybrid Textile Composites

Natural fibre-reinforced polymer composites are gaining considerable attention as sustainable alternatives to fully synthetic composites because of their low density, renewability, and favourable specific mechanical properties. However, the hydrophilic nature of natural fibres can result in poor fibre–matrix adhesion and restrict composite performance. In this study, hybrid laminates were fabricated using untreated, NaOH-treated, and KMnO4-treated ramie-fibre core layers sandwiched between carbon–Kevlar intraply hybrid outer layers through hand lay-up followed by compression moulding. The laminates were evaluated using tensile, flexural, Charpy impact, and short-beam shear strength tests, while scanning electron microscopy was employed to examine interfacial bonding and fracture mechanisms. The NaOH-treated laminate exhibited the best overall mechanical performance, achieving a tensile strength of 91.62 ± 4.32 MPa, a Young’s modulus of 2.94 ± 0.21 GPa, a flexural strength of 107.78 ± 4.37 MPa, and a flexural modulus of 4.73 ± 0.45 GPa. It also recorded the highest absorbed impact energy of 1.023 J, impact strength of 38.60 kJ/m2, and short-beam shear strength of 24.17 MPa. The improvements may be associated with modifications to non-cellulosic surface constituents, potentially promoting improved fibre-matrix interaction and more efficient stress transfer. The KMnO4-treated laminate generally exhibited intermediate performance between the untreated and NaOH-treated laminates. SEM observations supported the mechanical-test results by revealing improved interfacial bonding, fewer defects, and reduced fibre pull-out in the NaOH-treated specimens. Overall, NaOH treatment was found to be the most effective surface-modification method for improving the mechanical and interfacial performance of ramie/carbon–Kevlar intraply hybrid composites intended for sustainable, lightweight structural applications.