STRESS OVERSHOOT IN A MODEL PARTICLE GEL

Brownian dynamics simulation is used to investigate the large strain r heology of a model three-dimensional particle gel. The gel is formed f rom 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 earl ier work, bond breakage is introduced to the model allowing the study of structural disruption in response to large deformations. The accomp anying interparticle stress response reveals a distinctive stress over shoot characteristic of viscoelastic materials. Hookean and non-Hookea n bonding interactions have been studied, and for both cases the stres s 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 relative ly invariant. The limiting aggregate size at high strain-rates is depe ndent on the bond force as well as the energetic barrier to breakage. (C) 1997 American Institute of Physics. [S0021-9606(97)52541-4].