Brittle solid collapse to simple liquid for a waxy suspension.

We show that thanks to the existence of a continuous (percolating) network of weak interparticle bonds in a liquid, wax suspensions behave as "soft breakable (brittle) solids". It appears that, under the action of either a large stress over a short time or oscillating low stress (fatigue test), the initially solid network of these materials is broken and dispersed in the liquid, which makes them turn abruptly ("collapse") and irreversibly into a low viscous fluid. This collapse is more dramatic as the concentration increases. These phenomena are related to the evolution of the microstructure directly observed after different flow histories. The interpretation of these results provides new perspectives for understanding the physical origin of the brittleness or plasticity of solid or pasty materials, and suggests such materials might be used as model systems to simulate and explain natural catastrophic events such as landslides and avalanches.