Synergistic Enhancement of Tensile, Flexural and Interlaminar Shear Performance of Hemp/Epoxy Composites Through Fibre Surface Treatment, Fabrication Temperature Optimization and CNT Incorporation

Hemp-reinforced epoxy composites have gained attention in recent times owing to their unique properties like biodegradability, reduced carbon footprint, light weight, renewability, high wettability with epoxy, low carbon and low cost. However, the mechanical performance of hemp epoxy composites is adversely affected due to presence of impurities like lignin, hemicellulose and wax on the fibre surface and inconsistency in quality of hemp fibre available in market. This work demonstrates a novel integrated approach combining alkaline fibre treatment, optimization of hot pressing and post-curing conditions, and CNT reinforcement to enhance HFRE composites making them more durable structures broadening their domain of applications. This study initially employs an alkaline fibre treatment method using 5 w/w% NaOH solution, and subsequently addition of carbon nanotubes (CNTs) in epoxy matrix. Post-surface treatment of the fibre, FTIR and SEM analysis were carried out to observe the possible chemical and morphological changes of the fibre surface. The study also emphasizes the optimization of hot compression and post-curing temperatures for hemp fibre-reinforced epoxy (HFRE) composites. The laminates are partially cured during the hot pressing at different temperatures (40 °C, 60 °C and 80 °C) and further post-cured at two different temperatures (100 °C and 120 °C) for 6 h. After optimizing the hot press and post-curing temperatures, the CNT-incorporated HFRE were fabricated by adding CNT at different concentrations (0.1, 0.2 and 0.3 wt% with respect to epoxy) for enhancing the mechanical performance. The addition of 0.2% CNT to the HFRE composite resulted in the best mechanical performance among all the CNT-modified composite systems. Dynamic mechanical thermal analysis was employed to evaluate the viscoelastic behaviour of all composites across a temperature range. Fractographic studies were performed to comprehend the failure modes and correlate them with that of the mechanical performance of the composite materials.