Use of the Notched‐Beam Test for Evaluation of Fracture Energies of Ceramics

The mathematical analysis of the notched-beam specimen for fracture-energy determination considers a beam containing a zero-volume crack, i.e. a crack with zero width. Such a configuration is difficult to reproduce in practice with ceramics, and artificially cut notches with widths large relative to the scale of the ceramic microstructure are usually used. Evidence is presented which suggests that incorrect results can be obtained using such notches even when real cracks exist at the notch root. The effects of notch width and depth are examined for Al2O3, graphite, and SiC. A tentative specification of a root-crack-notch-radius relation is proposed for the application of this technique to ceramics.