Evaluation of Fracture Toughness, Flammability, and Mechanical Properties of Banana Fiber-Reinforced Epoxy Composites

The limited flammability resistance of natural fiber–reinforced epoxy composites remains a major barrier to their use in safety-critical structural applications. Although banana fiber is widely explored for mechanical reinforcement, its synergistic contribution to flame retardancy in hybrid systems with inorganic additives is not well established. This study develops a novel hybrid epoxy composite incorporating banana fiber (0–45 wt%), polypropylene (PP) yarn, and silica to enhance mechanical performance and fire resistance. Structural characterization using XRD and FTIR confirmed the semi-crystalline nature of banana fiber and functional group interactions that improve fiber–matrix adhesion. Composites were fabricated via hand lay-up and evaluated through tensile, flexural, fracture toughness, flammability, and morphological analyses. The 45 wt% banana fiber composite exhibited optimal mechanical properties, with tensile strength of 83.7 N mm⁻², flexural strength of 128 MPa, and fracture toughness of 2.76 MPa·m1/2. The lowest horizontal burning rate (29.94 mm/min) occurred at 35 wt% fiber loading due to enhanced char formation and silica-induced thermal shielding. TGA revealed reduced onset degradation temperature with increasing fiber content, while residual char increased from 9% to 29.8%. These findings confirm the dual role of banana fiber in reinforcing and improving flame retardancy in sustainable hybrid composites.