Investigation of the Influence of Multi-Walled Carbon Nanotubes on Laminate Composites During Progressive Tensile Damage Using Acoustic Emission

Progressive tensile damage for carbon fiber composites both containing and without multi-walled carbon nanotubes (MWCNTs) is discussed and this work is an extension of a previously published study. The composite specimens were subjected to progressive tensile experiments, and AE signals were collected during loading. The signals were post-processed using cluster analysis based on the Fuzzy C-Means algorithm. The results show that AE signals can be divided into three classes, corresponding to three damage modes: matrix cracking, fiber debonding, and fiber breakage. The AE peak frequency characteristics of each damage mode were found. Samples were also characterized using micro-computed tomography (Micro-CT) imaging and the observed damage shows good correlation with AE signal characterization for defect class prediction. Analyzing the data clusters it can be found that MWCNTs can delay and in some cases prevent both matrix cracking and fiber debonding in laminate composites. It was found that matrix cracking, debonding and fiber break AE signals for composites with CNTs correspond to a higher frequency range than that without CNTs. The results give guidance for composite design when considering MWCNTs and structure health monitoring of these composite materials.