Vincent Mazel 1,2, Pierre Tchoreloff 1,2,
1. Univ. Bordeaux, CNRS, Bordeaux INP, I2M, UMR 5295, F-33400, Talence, France
2. Arts et Metiers Institute of Technology, CNRS, Bordeaux INP, Hesam Universite, I2M, UMR 5295, F33400 Talence, France
Purpose. Tensile strength is a crucial property for pharmaceutical tablets, typically measured through the diametral compression test. Various test geometries are also outlined, such as the three-point bending test (USP, 1217), or the utilization of flattened disc geometry during diametral compression (Mazel et al., 2016). Results published in the literature reveal discrepancies among the values obtained from different tests. For instance, values obtained in the three-point bending test are generally around two times higher than those from the diametral compression test (Amorós et al., 2008; Hilden et al., 2016). This presentation aims to demonstrate how, through a combination of experimental and numerical studies, it is possible to elucidate these apparent disagreements.
Methods. Experimental work was conducted on tablets composed of various direct compression excipients (lactose, Mannitol, etc.) utilizing a compaction simulator, Styl’one evolution (Medelpharm). The specific flattened disc geometry was employed (Mazel et al., 2016). Various test configurations were utilized, including diametral compression and three-point bending. Numerical simulations were carried out using Finite Element Method (FEM) on the Abaqus software. Failure tests were simulated employing a cohesive zone model.
Results and conclusion. The challenge in comparing tests does not stem from the test configurations per se but rather from the method of deriving tensile strength using the breaking force. The conventional approach involves applying the maximum stress criterion. However, this criterion does not consider the stress distribution, resulting in the observed discrepancies. Conversely, numerical modeling with the cohesive zone model inherently addresses stress distribution, enabling a favorable agreement between the results obtained from various tests.
References
Amorós, J.L., Cantavella, V., Jarque, J.C., Felíu, C., 2008. Green strength testing of pressed compacts: An analysis of the different methods. J. Eur. Ceram. Soc. 28, 701–710.
Hilden, J., Polizzi, M., Zettler, A., 2017. Note on the Use of Diametrical Compression to Determine Tablet Tensile Strength. J. Pharm. Sci. https://doi.org/10.1016/j.xphs.2016.08.004
Mazel, V., Guerard, S., Croquelois, B., Kopp, J.-B., Girardot, J., Diarra, H., Busignies, V., Tchoreloff, P., 2016. Reevaluation of the diametral compression test for tablets using the flattened disc geometry. Int. J. Pharm. 513, 669–677.