Study of the validity of the three-point bending test for pharmaceutical round tablets using finite element method modeling.

Mechanical strength is an important quality attribute of the tablets produced in the pharmaceutical industry. The three-point bending test is one of the methods described by the United States (US) pharmacopeia to test this property. In this work, finite element method modeling was perform to study the stress distribution in a round, flat tablet submitted to this test and to verify whether the equation given by US pharmacopeia to calculate the tensile strength could be used without restrictions. For this test, the center of the lower face of the tablet was submitted to the highest tensile stress and, at this point, the stress state was nearly uniaxial. This test is thus well suited to measure the tensile strength of pharmaceutical tablets. Moreover, simulations were performed with a large range of geometrical dimensions using the dimensionless parameters D/L and h/D (where D is the tablet diameter, h is the tablet thickness, and L is the distance between the supports). In order to obtain the value of the tensile strength with a good precision when using the equation given by the US pharmacopeia, the measurements should only be performed in a restricted area of the domain defined by D/L and h/D.