Identification of weak interfaces in composites using transmission electron microscopy

A new experimental technique was developed to identify crack paths with a r esolution of nanometres in fibre-reinforced composites, Cracks were introdu ced through Vickers indentations on one side of the sample prior to startin g the thinning process. Indentations were placed close to the fibres in ord er to get enough cracks at the fibre/matrix interface in the electron-trans parent region of the thinned sample. The technique was used in a Nicalon-fi bre Al2O3 matrix composite prior to and after a heat treatment at 1200 degr ees C for 1 h. The analysis of the crack paths allowed the identification o f the weakest interface in each condition.