High-Temperature Bridging in a Vitreous Bonded Alumina

The load supported by crack wake bridges was studied in glassy alumina at 1240°C using short double cantilever beam specimens with a rear notch wedge. Direct observation of fracture surfaces revealed the sizes and shapes of the high‐temperature bridges. The bridged area was stochastic in nature but there was a clear trend toward decreased area bridged with increasing crack opening displacement consistent with existing models. Fracture surface observations on specimens without a rear notch were compared to bridge distributions in wedged specimens. Because of the complex bridge morphology the load supported by the bridges cannot be modeled as viscous uniaxial columns.