Assessment of Mechanical Strength, Thermal Stability, and Moisture Resistance of AA6061-Alumina-Banana Fiber Epoxy Fiber Metal Laminates

Fiber metal laminates (FMLs) exhibit potential as hybrid materials in structural applications, as they combine superior mechanical strength, thermal stability, and impact resistance. Complexities arise when attempts are made to enhance the mechanical strength and thermal response without increasing water retention levels. This research examines the effect of alumina concentration variations, ranging from 0 to 5%, on the mechanical and thermal properties of FMLs comprising AA6061 aluminum layers, banana fibers, and epoxy resin. The tests revealed that the sample containing 3% alumina in ABFA3 (Alumina-Banana Fiber Laminate) demonstrated the most significant tensile strength (148.6 MPa) and the highest flexural strength (253.6 MPa). It ensured enhanced load transfer capabilities alongside stronger fiber–matrix bonding. The outcome of the impact test showed that ABFA5 secured peak performance by absorbing 4.5 J of energy, resulting in improved impact tolerance. The addition of alumina in FMLs resulted in enhanced thermal stability, where ABFA5 reached its peak degradation temperature of 400 °C, the highest among all samples. The water absorption test revealed that alumina addition lowered moisture intake through ABFA5, which exhibited the best water absorption rate at 7.8%. The quasi-static indentation assessment revealed that ABFA5 achieved a maximum indentation force of 3783.65 N, demonstrating the highest energy absorption level and verifying its exceptional structural capability. Research findings indicate that a 3–5% alumina incorporation is the optimal composition for FMLs, as it achieves the ideal mechanical strength, thermal limits, and water resistance required by the automotive industry.