Synthesis and mechanical characterization of banana-hemp reinforced epoxy composites: Influence of fiber orientation

Abstract

Polymer composites reinforced with natural fibers, known as green composites, are favoured in engineering applications for their eco-friendly, biodegradable, recyclable, lightweight, and low-cost characteristics. Their sustainability and insulation capabilities make them ideal for modern applications in aerospace, automotive, and household items, replacing wood and various non-degradable polymer composites. This study investigated the influence of fiber orientation of banana-hemp unidirectional and bidirectional configurations on the mechanical characterization of epoxy-based hybrid polymer composites, developed through a universal hand lay-up technique. The impact of fiber orientation was analyzed through physical & mechanical characterization, including density, porosity, tensile, impact and flexural strength. The investigation revealed that the higher densities of banana and hemp fibers, relative to the epoxy matrix, enhanced the overall density of the hybrid composites, with bidirectional fiber orientation leading to higher porosity. Unidirectional hemp fiber-reinforced composites exhibited a substantial enhancement in tensile strength, outperforming banana, and banana-hemp composites by 71.80% and 9.96%, respectively, due to their strong interfacial bonding with the epoxy matrix. Additionally, unidirectional banana-hemp hybrid composites demonstrated a 12.18% increase in UTS and a 40.55% improvement in ductility compared to bidirectional counterparts. The highest flexural strength, recorded at 16.25 MPa, was achieved by unidirectional hemp fiber-reinforced laminated composites. Furthermore, hybrid banana-hemp composites showed a 63.59% higher flexural load capacity than bidirectional banana-hemp composites. However, bidirectional banana-hemp hybrid laminated composites exhibited the highest impact strength of 7.68 kJ/m2, surpassing unidirectional banana and hemp-reinforced composites by 21.90%. Fractographic analysis of banana/hemp fiber-reinforced epoxy composites revealed that unidirectional specimens experienced greater elongation before failure, with primary failure mechanisms including debonding, fiber pullout, and fiber scissoring.