Sustainable development of Himalayacalamus falconeri fiber/epoxy composites: Influence of bio-based bran fillers on fatigue and thermal behaviours

This study investigates the sustainable development of epoxy composites reinforced with Himalayacalamus falconeri fibers and bio-based bran fillers. Five composite variants (S0–S4) were fabricated with varying bran filler content while maintaining constant fiber loading to optimize mechanical, thermal, and flame-retardant performance. The S3 formulation exhibited superior multifunctional properties. Fatigue testing showed a peak stress of 35.4 MPa at 10000 cycles representing a 28% improvement over the unmodified control (S0), confirming enhanced durability under cyclic loading. Thermal conductivity was reduced by 26.9%, improving insulation, while the coefficient of linear thermal expansion decreased by over 10%, enhancing dimensional stability. The heat deflection temperature increased by 10.1%, demonstrating improved thermal load capacity. Thermogravimetric analysis revealed delayed degradation with DTG peaks near 360 °C, indicating higher thermal endurance. Dynamic mechanical analysis showed marked increases in storage modulus, loss modulus, and damping factor, reflecting superior stiffness, energy dissipation, and fiber–matrix interfacial bonding. Flame retardancy was also significantly enhanced, with ignition time extended by 34.3%, highlighting the fire-safe potential of the system. Overall, these findings establish the developed bio-composite as a lightweight, durable, and thermally robust material with strong promise for sustainable engineering applications. • Bran fillers improved fatigue life of bamboo composites by over 27% under cyclic load. • Thermal conductivity reduced by 27%, enhancing insulation and energy efficiency. • Dimensional stability improved with over 10% reduction in thermal expansion. • Flame retardancy improved by 34% with increased ignition delay time. • Storage modulus increased by 21%, boosting stiffness and vibration damping.