The deformation and fracture of a mullite fibre/alumina matrix ceramic ceramic-matrix composite material has been observed for the first time at 1100oC by by in situ synchrotron x-ray computed micro-tomography. The analysis, presented in the Journal of the European Ceramic Society, was carried out by Oxford Materials research student Talha Pirzada, with James Marrow, in collaboration with Dong Liu, Rob Ritchie and others at the Advanced Light Source in the USA.
3D visualisation of the microstructure showed fracture occurred by propogation of internal cracks at stresses close to the flexural strength. Shear fractures propogated across fibre bundles that were orientated perpendicular to the flexural stress at both room temperature and 1100oC.
At the higher temperature, an additional failure mode of delamination was observed, that may arise from relaxation of thermal residual stresses and creep.
You can read the full paper in Journal of the European Ceramic Society.