The measurement of the critical stress intensity factor ( KIC) of pharmaceutical powders using three point single edge notched beam (SENB) testing

Abstract

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.