Van der Waals-Driven Network Restructuring Explains Time-Dependent Piezoresistivity in Soft Nanocomposites

Abstract

Carbon-elastomer composites exhibit complex piezoresistive behaviour that cannot be fully explained by existing macroscopic or microstructural models. In this work, we introduce a network-based modelling methodology to explore the hypothesis that van der Waals interactions between carbon particles contribute to the formation of a conductivity-promoting network structure prior to curing. We combine a discrete aggregate-based representation of filler with a mesh-free, quasi-static viscoelastic model adapted from bond-based peridynamics, resolving equilibrium states through energy minimization. The resulting particle networks are analysed using graph-theoretic measures of connectivity and conductivity. Our simulations reproduce several unexplained experimental phenomena, including long-timescale resistivity decay, non-monotonic secondary peaks upon strain release, and the increasing prominence of these features with higher filler density. Crucially, these behaviours emerge from the interplay between viscoelastic stresses and van der Waals interactions. We show that the resistance response of the network operates over different characteristic timescales to the viscoelastic stress response. The approach has potential for understanding and predicting emergent behaviour in composite materials more broadly, where material characteristics often depend on percolating network structure.