Crack mouth opening displacement controlled fracture tests of brittle ceramics

Controlled fracture tests are required for the accurate determination of the toughness parameters of materials in order to assure the full conversion of the supplied energy into crack surface energy. From the three parameters involved in the test, load, displacement of the load point and crack mouth opening displacement (CMOD), this latter is the only one that continuously increases as fracture proceeds. Therefore, the CMOD has been proposed as control variable for the stable fracture tests. In this work, a new equipment to perform stable fracture tests of single edge V-notch beams (SEVNB) of ceramics in three points bending controlled by the CMOD is presented. The developed equipment allows performing stable fracture tests of extremely brittle materials. The equipment is presented together with results obtained for fine grained aluminium–magnesium aluminate and alumina ceramics.