Reevaluation of the diametral compression test for tablets using the flattened disc geometry

Abstract

Mechanical strength is an important critical quality attribute for tablets. It is classically measured, in the pharmaceutical field, using the diametral compression test. Nevertheless, due to small contact area between the tablet and the platens, some authors suggested that during the test, the failure could occur in tension away from the center which would invalidate the test and the calculation of the tensile strength. In this study, the flattened disc geometry was used as an alternative to avoid contact problems. The diametral compression on both flattened and standard geometries was first studied using finite element method (FEM) simulation. It was found that, for the flattened geometry, both maximum tensile strain and stress were located at the center of the tablet, which was not the case for the standard geometry. Experimental observations using digital image correlation (DIC) confirmed the numerical results. The experimental tensile strength obtained using both geometries were compared and it was found that the standard geometry always gave lower tensile strength than the flattened geometry. Finally, high-speed video capture of the test made it possible to detect that for the standard geometry the crack initiation was always away from the center of the tablet.

Breaking pharmaceutical tablets with a hole: Reevaluation of the stress concentration factor and influence of the hole size

“…Furthermore, several studies indicate that the interpretation of the results of the Brazilian test are not always straightforward [11,12]. In a previous study, we demonstrated that the use of cylindrical tablets did not make it possible to ensure a central failure during the diametral compression test [13]. The use of a flattened geometry ( Fig.…”

“…In our case symmetrical compaction was used. Two different sets of flat-faced euro B punches were used (ACM, Avilly-Saint-Leonard, France) as already described elsewhere [13]. The first set was round with a diameter of 11 mm.…”

“…In a previous article [13] the use of a flattened tablet to measure the tensile strength was introduced. Numerical simulations on the flattened geometry were thus also performed to see the influence of the flat parts on the SCF.…”

Finite Element Analysis and Modeling in Pharmaceutical Tableting

“…The largest number of the presented studies (35.6% of the total) deal with the stress/density distribution within the tablet during compression [ 5 , 15 , 27 , 61 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 ]. From these, 31.3% deal with the effect of punch shape [ 61 , 74 , 79 , 82 , 85 ].…”

Strength Simulation of Scored Tablets Based on the Finite Element Method Using an Extreme Vertices Design

“…By applying FEM, we can understand the physical behaviors of a complex object and predict the performance of a design such as the tableting process [2][3][4][5] and strength simulation. [6][7][8] The response surface method (RSM) is used to model the relationships between design variables and pharmaceutical responses. 9,10) A nonlinear RSM incorporating thin-plate spline interpolation (RSM-S) has been developed to determine the acceptable formulations of pharmaceutical compounds.…”