Comparative Study of Tensile Properties of Glass Fibre and Sisal Fibre Reinforced Polyester Composites

This study presents a comparative evaluation of the tensile properties of glass fibre reinforced polyester (GFRP) composites and sisal fibre reinforced polyester (SFRP) composites fabricated under identical processing conditions. The substitution of synthetic glass fibre with natural sisal fibre represents a direction toward sustainable composite materials with reduced environmental impact, and sisal cultivation in Nigeria's South West zone provides a readily accessible fibre source. Sisal fibres are extracted from Agave sisalana plants harvested in Oyo State, subjected to alkali treatment (5 percent NaOH, 4 hours, 60 degrees Celsius), and dried. Glass fibres are sourced from a commercial supplier. Both reinforcement types are used to fabricate composites at 10, 20, 30, and 40 percent volume fraction in unsaturated polyester resin by hand lay-up. Tensile specimens are cut per ASTM D638 and tested using a universal testing machine. Scanning electron microscopy is performed on fractured surfaces. Findings show that GFRP composites outperform SFRP composites at all fibre fractions in ultimate tensile strength, with a maximum value of 142 MPa at 30 percent versus 64 MPa for SFRP at equivalent fraction. However, SFRP composites exhibit comparable specific strength values at 20 percent volume fraction due to the lower density of sisal relative to glass fibre. Alkali treatment significantly improves SFRP tensile performance compared to untreated fibre composites. Keywords: sisal fibre, glass fibre, polyester composite, tensile properties, natural fibre.