Pantnagar Journal of Research

Abstract

Researchers have recently shifted their focus toward natural fibre-reinforced polymer composites due to their superior ecological friendliness and environmental sustainability compared to synthetic counterparts. Among the diverse sources of natural reinforcement, Grewia optiva (locally known as Bhimal) has emerged as a promising plant fibre. This study investigates the development of epoxy matrix composites reinforced with short, untreated Grewia optiva fibres at lengths of 5 mm, 10 mm, and 15 mm. A key novelty of this research is the mechanical purification of the fibres extracted via the traditional water-retting method using an iron strand brush to remove the surface impurities without any chemical treatment. Experimental characterization revealed that these fibres possess an average density of 1.232 g/cm³. For composite fabrication, the epoxy resin and hardener were mixed in a volume ratio of 100:12. Mechanical testing indicated that a 5 mm fibre length and 30% volume fraction optimize the Ultimate Tensile Strength (62 MPa) and Flexural Strength (119.8 MPa), as this configuration ensures effective stress transfer without structural defects. Conversely, the minimum water absorption was achieved at 5 mm/20% due to reduced hydrophilic content, while the maximum elongation (4.67%) occurred at 5 mm/40%, where shorter fibres allowed for greater interfacial slippage. These findings highlight the critical role of optimizing fibre geometry and volume fraction in tailoring biocomposite properties for specific engineering applications.