Enhanced crashworthiness of aluminum crashboxes using sustainable galam bark fiber honeycomb composite fillers under quasi-static compression

The increasing demand for lightweight and energy-efficient vehicle structures has intensified the need for sustainable materials with high crashworthiness performance. However, the integration of biomass-derived materials as internal energy absorbers in thin-walled structures remains limited. In particular, galam bark ( Melaleuca leucadendra ), which is commonly discarded as waste, has not been systematically explored for crashworthiness applications. This study investigates the crashworthiness performance of aluminum crashboxes filled with a galam bark-based honeycomb composite under quasi-static axial loading. Three configurations were examined: an empty crashbox (Base), an epoxy-based composite-filled crashbox (CHE), and a polyester-based composite-filled crashbox (CHP). A stress-based trigger design was introduced to control collapse initiation. Quasi-static compression tests and scanning electron microscopy (SEM) were employed to evaluate structural response and failure mechanisms. The CHE configuration achieved the highest energy absorption of 3.11 kJ, representing an increase of approximately 44% compared to the Base model (2.15 kJ), while reducing the initial peak force by approximately 45%. The maximum specific energy absorption reached 15.39 kJ/kg, indicating improved energy absorption efficiency. SEM analysis revealed that strong fiber–matrix interfacial bonding promotes efficient stress transfer and stable progressive failure, whereas CHP exhibited dominant fiber pull-out and interfacial sliding. The findings demonstrate that biomass-derived galam bark honeycomb composites have the potential to function as sustainable and lightweight internal energy absorbers for aluminum crashbox systems under quasi-static loading conditions, offering a promising pathway for biomass waste valorization and the development of environmentally responsible crashworthy structures.