Stress overshoot in a model particle gel

Brownian dynamics simulation is used to investigate the large strain rheology of a model three-dimensional particle gel. The gel is formed from soft spherical particles incorporating flexible surface-to-surface bonds which restrict the angular reorganization of fractal aggregates resulting in a stable, percolating, network structure. Extending earlier work, bond breakage is introduced to the model allowing the study of structural disruption in response to large deformations. The accompanying interparticle stress response reveals a distinctive stress overshoot characteristic of viscoelastic materials. Hookean and non-Hookean bonding interactions have been studied, and for both cases the stress maximum scales as a power law close to the square root of the strain-rate, while the strain at which the stress maximum occurs is relatively invariant. The limiting aggregate size at high strain-rates is dependent on the bond force as well as the energetic barrier to breakage.