Engineering sustainable composites: Role of fibre sequence and treatment in sisal/ramie vinyl ester composites

This study investigated the impacts of fibre stacking sequence and sodium hydroxide treatment on the mechanical properties of sustainable sisal/ramie hybrid vinyl ester composites. Fourier transform infrared analysis (FTIR) revealed significant chemical changes in treated fibres, including increased fibre purity due to the removal of hemicellulose and portions of lignin, resulting in more hydroxyl groups. These changes enhanced the interaction between fibres and the matrix, thereby improving the mechanical properties of the composites. Among various stacking sequences, the ramie/sisal/sisal/ramie (C6) configuration exhibited the highest Shore‐D hardness (61.2 D), tensile strength (30.83 MPa), and tensile modulus (0.84 GPa), attributed to the strategic placement of ramie layers in load‐bearing positions. This configuration also demonstrated superior flexural strength (63.33 MPa) and flexural modulus (2.02 GPa) due to the balanced distribution of stress between the matrix and fibres. Scanning electron microscopy (SEM) images confirmed that alkali treatment improved fibre‐matrix adhesion, reducing defects such as fibre pullout and matrix cracks. The findings highlight that both fibre stacking sequence and alkali treatment play a crucial role in enhancing the mechanical performance of natural fibre composites, making them suitable for applications demanding high strength and durability.