Quasi-static indentation damage and residual compressive failure analysis of carbon fiber composites using acoustic emission and micro-computed tomography

In present research, the internal damage evolution and failure characteristics of carbon fiber woven composites under indentation and residual compressive loads were studied by using acoustic emission technology and X-ray micro-computed tomography. Real-time acoustic emission signals originating from internal damage of composites under applied loads were obtained and analyzed by the k-means clustering algorithm. Moreover, the internal damage characteristics were observed by the reconstructed three-dimensional model and the slice images of composite specimens. The results showed that the higher the indentation force reading, the more acoustic emission signals with high amplitude and frequency (over 300 kHz) are generated. Furthermore, the early acoustic emission signals with high-frequency were observed under residual compressive loads. It can be attributed to serious failures of fibers with the increase of static indentation loads. In addition, the internal damages such as delamination, debonding, crack and fiber breakage can be clearly characterized by micro-computed tomography and scanning electron microscopy observation. The complementary technology combing acoustic emission with micro-computed tomography can provide a better understanding of internal damages and evolution behaviors of the composites.