Use of cylindrical samples for ceramics strength measurements

In spite of his great applied interest, the tensile strength of brittle materials, and chiefly that of ceramics, is difficult to measure directly by classical tensile tests. This results from the difficulties induced both by the samples machining and their grip on the testing machine. So, it is common to perform indirect determinations on the basis of strength values obtained in 3 or 4 points bending tests on prismatic samples. In the case of massive or hollow cylindrical samples, the diametral compression tests seem to be the best measurement technique, but these tests require refined experimental approach to lead to significant results. In order to characterise these care, two original experimental devices, one dedicated to massive cylinders, the other to hollow cylinders, have been built. The comparison of results thus obtained with those given by the classical bending tests permits to specify the validity and the limits of the techniques here developed