Optimization of Nanofillers Distribution to Inhibit Electrical Tree Growth in Composites

Inorganic nanofillers have been incorporated to enhance the electrical treeing resistance of polymers. However, the influence of nanofiller shape and distribution remains not fully understood, thereby limiting the advancement of new insulation design strategies. This work presents a phase-field model to simulate the propagation of electrical tree in nanocomposites and quantitatively compare the effectiveness of different filling schemes. The damage status of insulation is described with a spatially and time dependent continuous variable, and the evolution of damage phase is modeled with the kinetic equation. The results indicate that nanofillers act as physical barriers to electrical-tree growth. Due to the competition between the hindrance effect and electric-field enhancement of nanofillers, the nanocomposite containing 8 vol% Al2O3 nanoparticles exhibits the optimal electrical-treeing resistance, with the breakdown time increasing from 767.5 s for neat PE to 827.1 s, corresponding to an improvement of 7.77%. The electrical-tree resistance is closely related to the shape and orientation of the nanofillers. Compared with neat PE, randomly distributed and parallel nanosheets increase the breakdown time by 12.04% and 27.00%, respectively, and exhibit stronger inhibition of electrical-tree growth than nanoparticles and nanofibers. High-throughput computations are further performed to analyze the effects of nanofiller shape and orientation on electrical-tree characteristics. When the electrical-tree propagation direction is perpendicular to the nanosheets, increasing the aspect ratio from 2 to 12 raises the normalized breakdown time from 1.07 to 1.36.