Role of nickel oxide nanoparticle and cattail fiber reinforced vinyl ester biocomposite, and their performance on fatigue, creep, flammability, water absorption and machining studies

This study systematically investigated the synergistic effect of silane-modified cattail fiber and nickel oxide (NiO) nanoparticles on the multifunctional performance of vinyl ester biocomposites. The novelty of this work lies in simultaneously optimizing fatigue resistance, creep behavior, moisture resistance, flammability, and machinability within a single hybrid composite system. Composites containing a fixed 30 vol.% cattail fiber and varying NiO loadings (0, 1, 3, and 5 vol.%) were fabricated, with neat vinyl ester used as the reference. Results showed substantial enhancement in fatigue performance through hierarchical reinforcement mechanisms. The optimum fatigue specimen (B4: 30 vol.% fiber +3 vol.% NiO) achieved 24,711, 21,711, and 18,741 cycles at 25%, 50%, and 75% UTS, respectively, representing nearly sevenfold improvement over neat resin. In contrast, the highest nanoparticle loading (B5: 5 vol.% NiO) exhibited superior creep and environmental resistance, with creep strains reduced by nearly 50% compared to the baseline. Water absorption decreased to 1.32%, while flammability resistance improved with a lower flame propagation rate of 6.14 mm/min due to the barrier and char-forming effects of NiO nanoparticles. Drilling analysis further revealed reduced dimensional deviation and minimal delamination in B5, confirming enhanced machinability. Morphological studies indicated a transition from brittle fracture and fiber pull-out to compact, defect-resistant structures after nanoparticle incorporation. CCD-RSM optimization identified approximately 4 vol.% NiO as the optimal composition for balanced multifunctional performance.