A correlation between angle of friction, angle of failure plane and strength for compacts of tartaric acid, microcrystalline cellulose and mixture of the two

The angle of shearing resistance ø and the direction of the failure plane when two powders (tartaric acid and microcrystalline cellulose) and a mixture of these two powders underwent uniaxial compaction were calculated from the applied and radial stresses produced in an instrumented punch and die assembly. A tridimensional representation of the compacting process involving all three parameters associated with compaction — the shear stress, τ, normal stress σ and compact volume V — showed that the ratio of shear stress to normal stress on the failure plane remained constant during the last stages of densification for tartaric acid and mixtures. A logarithmic correlation existed between the diametral crushing strength, σ t , of the resultant compacts and both the angle of shearing resistance and the angle of the failure plane in the compacting materials.