Evaluation of crack-tip stress fields on microstructural-scale fracture in Al–Al2O3 interpenetrating network composites

The influence of local microstructure on the fracture process at the crack tip in a ceramic–metal composite was assessed by comparing the measured stress at a microstructural level and analogous finite element modelling (FEM). Fluorescence microprobe spectroscopy was used to investigate the influence of near-crack-tip stress fields on the resulting crack propagation at the microstructural scale. The high spatial resolution was effective at mapping the localized crack-tip stress distributions within the complex Al–Al₂O₃ phase morphologies, where the localized stress distribution about the crack tip within the Al₂O₃ phase could be measured. Regions of high-localized tensile stress within the microstructure resulting from a combination of applied load and thermal residual stress were identified and could be used in predicting the subsequent crack extension direction. Stress distributions calculated from spectroscopy results were compared with microstructural level FEM of the same structure and general agreement between the two techniques was observed.