Characterization of unidirectional hybrid kenaf/glass bio-composites: Experimental and analytical study

Natural fiber composites are gaining recognition as sustainable alternatives for lightweight structural applications, yet achieving a balance of strength, toughness, and durability remains a persistent challenge. This study investigates continuous hybrid unidirectional kenaf/glass fiber-reinforced epoxy composites (HKGFRP) at three fiber volume contents (10%, 30%, 40%) and varying glass portions. The experimental evaluation included tensile testing, analysis of variance (ANOVA), and scanning electron microscopy (SEM), while analytical predictions were obtained using the adopted rule of mixtures (AROM). Results show that at 30% fiber volume, the hybrid with 10% glass fiber achieved 18% higher ultimate tensile strength and 30% greater strain energy density compared to kenaf fiber composites, while also exhibiting improved ductility. SEM analysis revealed reduced interfacial debonding at the optimum, whereas higher glass fiber portions led to premature failure due to strain-to-failure mismatch. AROM predictions closely matched experimental data, validating the model’s applicability. Based on the observed limitations of layered hybrid composites, particularly debonding failures at the interfaces, filament-level hybridization is proposed as a promising future fabrication strategy to enhance mechanical performance and long-term sustainability of bio-composites for structural engineering.