(87f) The Diametrical Compression Test as a Strength Prediction Method for Pharmaceutical Compacts

Authors: 
Sinha, T., Purdue University
Bharadwaj, R., Pfizer Inc.


The diametrical compression test (a.k.a. Brazilian disk test, hardness test) is a common testing technique used in the pharmaceutical industry. The test produces an indirect tensile failure of the compact and, hence, provides a measure of the maximum force that can be sustained by a tablet before fracture. Due to the ease of performing this test, it is widely used as a control parameter during tablet compaction in order to prepare tablets with an acceptable mechanical strength.

The Finite Element Method (FEM) is used to investigate the anisotropy and plasticity generated during tablet compaction on the stresses produced within compacts during diametrical compression. Simulation results show that cracks initiate differently on both faces of the tablets resulting in a non-uniform stress profile along the thickness of the tablet. A constant stress value is assumed in the Hertzian/Hondros analytical solution which is commonly used to evaluate the maximum tensile force. High speed video experiments of the diametrical compression test show the non-uniform cracking behavior observed in the FE simulations. The current study highlights the influence of material heterogeneity on tablet strength.