Effects of microstructure on the compressive yield stress

The effects of microstructure on the compressive properties of aggregated a lumina suspensions are determined by intentionally introducing heterogeneit ies into the suspension. Suspensions are prepared at a high volume fraction and diluted with low hear hand mixing to a series of initial concentration s. As the initial concentration is increased, larger heterogeneities are in troduced, and the suspension becomes more compressible relative to the comp ressive yield stress of the uniform suspension. A simple model is proposed in which the heterogeneous suspensions compress by rearrangement of the den se aggregates until a critical concentration (phi(c), which coincides with the volume fraction prior to dilution) is reached. Above phi(c), the suspen sions consolidate identically to the uniform suspension. With a single fitt ing parameter (the size of the heterogeneities), the model shows semiquanti tative agreement with the experimental data.