Damage monitoring and identification in SiC/SiC minicomposites using combined acousto-ultrasonics and acoustic emission

The acoustic emission (AE)-based technique is considered to be a promising way to real-time monitoring of microstructural changes and damage evolution in Ceramic Matrix Composites (CMCs). The present paper proposes a testing protocol that combines acousto-ultrasonics (AU) and acoustic emission (AE) monitoring, with a view to obtain both global and local definite characteristics on damage modes and kinetics. It is developed and assessed on SiC/SiC minicomposites, which are appropriate test specimens to establish sound relations between mechanical behavior and damage modes. AU wave velocity measurements provide a global measure of matrix cracking damage and the relations between crack growth and damage characteristics. AE monitoring allows accurate localization of AE sources taking into account wave velocity dependence to damage as well as differentiation of the damage modes, which control the mechanical behavior. Finally, multivariate analysis of AE data allowed classification of signals into clusters, which were successfully associated to the various damage modes.