Mechanical and environmental characterization of epoxy-based hybrid composite reinforced with banana, flax, and carbon fibers for structural applications

This study examines the mechanical and environmental performance of an epoxy-based hybrid laminate reinforced with carbon, flax, and banana fibres. The laminate was fabricated using a hand lay-up technique followed by compression moulding, maintaining a fibre-to-matrix weight ratio of 40:60 and a symmetric stacking sequence of M/C/M/F/M/B/M/F/M/C/M. Mechanical characterization was conducted through tensile, flexural, impact, and hardness tests in accordance with relevant ASTM standards, with tensile testing performed as per ASTM D3039. Environmental durability was assessed via water absorption testing, and density was measured using the Archimedes principle. The hybrid laminate exhibited an average tensile strength of 2.09 ± 0.02 MPa with a failure strain of 5.3 ± 1.0%, indicating progressive damage behaviour associated with natural fibre hybridization. Improved flexural load-bearing capability was achieved due to carbon fibre placement on the outer layers, while impact testing revealed enhanced energy absorption governed by flax fibre fibrillation and banana fibre crack-bridging mechanisms. Rockwell hardness (HRB) values exceeded those of fully natural fibre composites, confirming the stiffening effect of carbon fibre skins. Water absorption after 24 h immersion was reduced by 44–63% compared to natural fibre laminates, demonstrating effective epoxy encapsulation and moisture-barrier behaviour. The results highlight the potential of controlled natural–synthetic fibre hybridization for lightweight semi-structural applications requiring moderate strength and improved environmental resistance.