title: Comparison of different failure tests for pharmaceutical tablets: applicability of the Drucker-Prager failure criterion.
abstract: Several tests can be used to study the strength of pharmaceutical tablets. Equations exist in the literature to transform the failure force measured into a failure stress which can be considered as a characteristic of the strength of the material. For each failure test, the stress state at failure is different, and as a consequence, the failure stresses obtained are also different. It would thus be interesting to find a failure criterion to unify the different results. In this study four different tests were performed on pharmaceutical compacts of various densities: diametral compression, three-point flexure, biaxial flexure and uniaxial compressive tests. The Drucker-Prager criterion was tested as a possible fracture envelope. The results showed that this criterion is well suited to explain the failures obtained by diametral compression, three-point flexure and biaxial flexure. Nevertheless, for the uniaxial compressive test, the use of this criterion led to a significative underestimation of the experimental value of the failure stress. As a consequence, the Drucker-Prager criterion must be used with caution and is not able to explain all the failures that can occur in a pharmaceutical compact.
authors.affiliation: Univ Paris-Sud, EA 401, Matériaux et Santé, 5 rue Jean Baptiste Clément, Chatenay Malabry 92296, France. Electronic address: vincent.mazel@u-psud.fr.
authors.forename: Vincent
authors.initials: V
authors.lastname: Mazel
authors.affiliation: Univ Paris-Sud, EA 401, Matériaux et Santé, 5 rue Jean Baptiste Clément, Chatenay Malabry 92296, France.
authors.forename: Harona
authors.initials: H
authors.lastname: Diarra
authors.affiliation: Univ Paris-Sud, EA 401, Matériaux et Santé, 5 rue Jean Baptiste Clément, Chatenay Malabry 92296, France.
authors.forename: Virginie
authors.initials: V
authors.lastname: Busignies
authors.affiliation: Univ Paris-Sud, EA 401, Matériaux et Santé, 5 rue Jean Baptiste Clément, Chatenay Malabry 92296, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Tchoreloff
mesh_terms: D002130:Calcium Phosphates / Q000737:chemistry*; D019245:Compressive Strength; D011208:Powders; D013314:Stress, Mechanical; D013607:Tablets; D013678:Technology, Pharmaceutical / Q000379:methods*
chemical_list: D002130:Calcium Phosphates; D011208:Powders; D013607:Tablets; C020243:calcium phosphate
keywords: Biaxial flexure; Diametral compression; Tablet; Tensile strength; Three-point flexure; Uniaxial compressive test