Determination of tablet strength by the diametral-compression test.

The strength of lactose tablets has been measured by application of the diametral-compression test. The relative value of tensile, compressive, and shear stresses within the tablet varies, depending on the characteristics of the tablets and the surface providing the applied compression. It has been shown that to obtain reproducible results for the strength of tablets prepared at a given compression force, the tablet must break in such a manner that the tensile stress is the major stress. For a given tablet, this may require the placing of suitable padding material between the tablet and the compressing surfaces. Assessment of the type of failure can be made visually and under the correct conditions, the results expressed as a tensile strength. There are, however, a range of conditions which ensure tensile failure resulting in different values for the tensile strength. These values are characteristic of the tablet and test conditions and are not absolute values of tensile strength.