Aging behavior of chemically treated bamboo/carbon fiber-reinforced hybrid composites: Evaluation of mechanical, acoustic, and vibrational properties

Hybrid natural/synthetic fiber composites are gaining traction as sustainable alternatives in structural and functional applications. However, their long-term durability under environmental aging remains inadequately understood, particularly in terms of combined mechanical, vibrational, and acoustic performance. Existing literature predominantly addresses singular performance metrics or isolated aging conditions, leaving a research gap in the integrated evaluation of these properties under multifactorial degradation environments. This study investigates the influence of potassium permanganate and sodium hydroxide treatments on the aging resistance of bamboo/carbon fiber-reinforced epoxy hybrid composites. Laminates were subjected to ambient, subzero, and ultraviolet (UV) aging conditions. Moisture absorption behavior was analyzed. Vibration damping characteristics were evaluated using the impact hammer technique and the half-power bandwidth method, while sound absorption was measured using an impedance tube setup based on the two-microphone transfer function method. Tensile and flexural tests were conducted to quantify the functional and structural deterioration of aged laminates. Results show that sodium hydroxide-treated composites consistently outperformed potassium permanganate-treated counterparts, exhibiting up to 26.6 % lower moisture uptake and significantly better retention of mechanical and damping properties across all aging conditions. UV aging led to the most pronounced degradation, with tensile and flexural strength reductions of 55.9 % and 46.0 %, respectively, in potassium permanganate-treated composites. In contrast, sodium hydroxide-treated composites demonstrated improved interfacial stability, resulting in enhanced mechanical and acoustic performance under accelerated aging. This comprehensive study highlights the critical role of fiber surface chemistry in determining the long-term durability of natural fiber-based hybrid composites. The findings support the selection of sodium hydroxide treatment for applications requiring extended environmental exposure, offering valuable insights for the design of resilient, bio-based composite systems.