Optimizing Water Absorption Resistance of Jute Fiber Composites Through Al ₂ O ₃ Nanoparticle Incorporation: Predictive Modeling Across Multiple Aqueous Environments

This study addresses this challenge by investigating aluminum oxide (Al2O3) nanoparticle incorporation as a moisture barrier strategy in bidirectional jute fiber-reinforced epoxy composites. Composites containing 30 wt.% jute fibers were fabricated via hand lay-up compression molding with systematic Al2O3 loadings (0,5,10,15 and 20 wt.% relative to epoxy matrix, α-phase, µ particle size, ≥ 99.5% purity). Water absorption kinetics were evaluated across three distinct aqueous environments distilled water, rainwater, and seawater over 504 hours of continuous immersion. Response surface methodology with optimal design established predictive quadratic models correlating absorption behavior with immersion time, Al2O3 content and liquid type. Results revealed that 20 wt.% Al2O3 content and liquid type. Results revealed that 20 wt.% Al2O3 loading achieved optimal moisture resistance, reducing water absorption by 25.2% in seawater (11.33% vs. 15.15% unfilled), 18.4% in rainwater (15.13% vs. 18.54%) and in distilled water (14.47% vs. 17.39%). The developed model demonstrated exceptional predictive accuracy (R2 = 0.9914, predicted R2 = 0.9791) with external validation at intermediate loadings (5 and 15 wt.%), confirming superior interpolation capability (R2va = 0.9936). Environmental aggressiveness followed the hierarchy: rainwater > distilled water > seawater, attributed to acidic degradation, neutral diffusion, and osmotic resistance mechanisms, respectively. This work establishes quantitative design guidelines for moisture-resistant natural fiber composites suitable for marine structures, outdoor construction, and humid-environment.