Enhancing energy absorption of luffa–cenosphere-reinforced epoxy composite: Influence of surface modification of reinforcements

This study focuses on the development and impact performance of lightweight hybrid composites (LCE) reinforced with luffa fibers and cenospheres. Luffa fibers underwent surface modifications using acetic acid, benzoyl chloride, and potassium permanganate, while cenospheres were chemically treated with a silane agent 3-triethoxysilyl-propylamine (T-TESPA) to improve their compatibility with the epoxy matrix. The L16 array was created according to Taguchi’s DOE, and the LCE composite was fabricated accordingly. Microstructural analysis confirmed that the fibers and fillers were evenly distributed within the matrix. FTIR and TGA results showed that the treatments enhanced chemical functionality, thermal stability, and interfacial bonding of reinforcement with matrix. Impact testing revealed that the composites exhibited clear patterns of damage initiation and peak load capacity. Among all tested samples, LCE08—made with benzoyl chloride–treated fibers, T-TESPA-modified cenospheres at 20% filler volume, and one fiber layer—showed the best performance, achieving the highest peak force (1103.44 N), the lowest coefficient of restitution, and the most significant energy absorption, 37% higher than the untreated baseline LCE01. Based on the findings from the tested samples, the optimized parameters for the LCE composite—as determined through Taguchi’s DOE—were identified as benzoyl chloride–treated luffa fibers, a 20% filler volume, T-TESPA-modified cenospheres, and the inclusion of two fiber layers, resulting in superior energy absorption. Fractographic studies confirmed improved crack deflection, energy dissipation, and interfacial adhesion. This work demonstrates that combining natural fibers and modified fillers with optimized processing significantly enhances the mechanical performance, energy absorption, and impact resistance of lightweight composites. These materials show great promise for advanced structural applications requiring high durability and energy dissipation.