Fractured surface analysis of nickel ferrite natural rubber nanocomposites using digital imaging

Flexible nickel ferrite–natural rubber nanocomposites were developed and systematically investigated to elucidate structure–property–fracture relationships relevant to functional elastomeric applications. Sulfur-cured composites containing varying concentrations of nickel ferrite were evaluated for their mechanical performance, with particular emphasis on tear behavior. A reduction of 28% in tear strength was found when filler loading was increased to 80 phr (parts per hundred parts by weight of rubber). Fracture surfaces were examined using Scanning Electron Microscopy (SEM). Digital image processing using ImageJ combined with BoneJ-based fractal analysis was employed to quantitatively characterize fracture complexity. The evolution of fractal dimension, D B from 1.175 for blank rubber to 1.659 for 120 phr nickel ferrite loaded nanocomposite revealed a transition from matrix-dominated ductile fracture to agglomeration-assisted crack propagation. Enhanced crack branching and surface heterogeneity at higher filler contents resulted in increased fractal dimension, reflecting greater fracture surface complexity. These findings demonstrate that fractal dimension serves as a robust quantitative descriptor linking filler dispersion, agglomerate growth, and mechanical response. The insights gained are directly relevant to the design of flexible magnetic materials for applications such as sensors, electromagnetic interference shielding, and soft magnetic components.