Non-destructive monitoring of damage accumulation in woven-fabric carbon/carbon composites is a topic of high interest due to the increased use of such materials in structural components for the aerospace, automobile and defense industries. Acousto-ultrasonics (AU) is a non-destructive technique that utilizes two typical acoustic emission sensors one as a pulser and the other as a receiver. During tensile load-unload-reload tests the pulser emits an ultrasonic pulse, which in the form of elastic wave propagates through the test specimen and is captured by the receiver. As damage accumulates into the material structure the ultrasonic pulse interacts with the damaged microstructure and changes its characteristics often in a subtle not obvious manner. Consequently, sophisticated signal processing methods are needed to extract the hidden information from the recorded AU waveforms in order to identify the type of damage and quantify its severity. The diffuse field decay rate method and wavelet-based methods were applied in order to process the AU waveforms and extract damage sensitive parameters. Two types of C/C composites with different interface concepts were tested and the applied technique elucidates the damage evolution developed during cyclic loading and associated with the different interface concepts.