THE MEASUREMENT OF THE CRITICAL STRESS INTENSITY FACTOR (K(IC)) OF PHARMACEUTICAL POWDERS USING 3 POINT SINGLE EDGE NOTCHED BEAM (SENB) TESTING

The critical stress intensity factor, K(IC), of a number of pharmaceutical materials has been determined using a three-point single edge notched beam (SENB) technique. The technique was initially validated using microcrystalline cellulose and the value of the critical stress intensity factor at zero porosity, K(ICo) of microcrystalline cellulose was found to compare reasonably well to literature data determined by four-point SENB testing. The technique utilising sawn notches was tested on a number of other important pharmaceutical materials ranging from excipients to drugs including aspirin, ibuprofen and paracetamol, It was found in general that organic pharmaceutical materials are primarily brittle or semi-brittle in their mechanical response to stress based on a brittleness index, defined as the ratio of indentation hardness to the critical stress intensity factor.