Epoxy-based biocomposites reinforced with alkali-treated coir fibers and bamboo fillers for lightweight applications: Unravelling of physicomechanical, chemical, structural, and microstructural characteristics

This study develops a novel biocomposite using coir fiber and bamboo filler in an epoxy matrix. The density of alkali-treated coir fiber was found to be decreased from 1470 ± 20 kg/m 3 to 1284 ± 24 kg/m 3 , while the bamboo filler density reduced from 965 ± 24 kg/m 3 to 846 ± 19 kg/m 3 , indicating successful reduction in fiber density for lightweight composite applications. Alkali treatment led to a significant 58.8% increase in tensile strength of the coir/epoxy composite, rising from 28.63 MPa to 45.45 MPa. Incorporation of bamboo filler further enhanced the tensile strength by 89.5%, reaching 54.26 MPa. Flexural strength also improved, with untreated coir/epoxy composites showing 25.75 MPa, increasing to 28.26 MPa post-alkali treatment (a 9.75% enhancement) and to 31.35 MPa with bamboo filler (21.74% increase). Impact resistance significantly improved, with the coir/epoxy composite’s impact strength rising from 26.43 kJ/m 2 to 31.45 kJ/m 2 after alkali treatment (a 19.01% increase) and to 34.56 kJ/m 2 with bamboo filler (30.78% increase). The biocomposite also exhibited reduced moisture absorption, with the highest moisture absorption observed being 6.76% for NaOH-treated coir/epoxy composites and 4.32% for composites containing both coir and bamboo fillers. This study demonstrates that integrating alkali-treated coir fiber and bamboo filler produces a lightweight, eco-friendly composite with superior mechanical performance, offering a promising alternative to conventional materials.