Mechanical and hygrothermal evaluation of natural fiber hybrid epoxy composites using Borassus flabellifer fruit fiber and snake grass fiber with gum enhancement

Mechanical, microstructural, and hygrothermal behaviours were studied for hybrid epoxy composites reinforced with Borassus flabellifer fruit fiber (BFF), snake grass fiber (SGF), and gum Arabic. Six composites were fabricated with varying BFF-SGF ratios while maintaining constant epoxy (60%) and gum Arabic (10%) content. The composites were evaluated for tensile, flexural, impact, hardness, interlaminar shear strength (ILSS), density, water absorption, thickness swelling, and microstructural morphology using scanning electron microscopy (SEM). Hybridization significantly improved the overall structural performance of the composites. Among all compositions, the C3 composite (15% BFF / 15% SGF / 10% gum Arabic) exhibited the highest tensile strength (72 MPa), flexural strength (89 MPa), impact strength (28 kJ/m²), hardness (79 Shore D), ILSS (42 MPa), and density (1.21 g/cm³), and the lowest water absorption (6.1%) and minimum thickness swelling (1.53%) after 72 h. SEM analysis revealed improved fiber-matrix interfacial bonding, reduced void content, and uniform gum dispersion in the hybrid composites, which contributed to their superior performance. In contrast, single-fiber and gum-free composites demonstrated lower mechanical and hygrothermal performance due to weaker interfacial adhesion and non-uniform stress transfer. These findings indicate that BFF-SGF hybrid composites are promising materials for lightweight structural and semi-structural applications.