Modelling Mechanical Response of SiC/CAS-II Ceramic Composite under Quasi-Static Loads Using a Real-Time Acousto-Ultrasonic NDE Technique

The onset of matrix cracks and their progression have been successfully monitored by an acousto-ultrasonic (AU) NDE technique as shown by the authors in previous work. The nonlinear behavior observed in a stress-strain curve for a unidirectional ceramic composite has been predominantly attributed to the effect of matrix cracks. This effect of matrix cracks on the stress-strain curve has been previously modelled (AUSSR model) with the help of real-time AU data. The models presented in this paper (modified AUSSR, AUSSR-WZ, AUSSR-WZ-WB models) attempt to describe the damage mechanisms occurring by assessing the combined effect of matrix cracks and fiber breakage on the global strain response of the laminate to increasing loads. The strains at the outer surface predicted by the models described in this paper are compared to the experimentally observed strains from the extensometer attached to the outer surface. Previous models from the literature are introduced outlining the history of development of successive models. It is shown here that the modified acousto-ultrasonic stress-strain response (modified-AUSSR) model based on AU parameters is capable of predicting the strain response to increasing stress levels for unidirectional and cross-ply ceramic composite laminates. This work represents an integration of measured experimental damage with analytical modelling to produce a better physical understanding of the damage development process in ceramic composites.