Challenges in micro-CT characterization of composites

Studies related to defect investigation of composite materials with X-ray based computed tomography mostly focus on the void presence inside materials and its impact on the mechanical behavior of composites. This chapter focuses on the localization and the quantitative investigation of processing related anomalies like pore formation, sticking and spreading of tows during a vacuum infusion process of glass fiber unidirectional Non-Crimp Fabric (NCF) of four different yarn numbers but with constant areal weight. A case study is presented in order to provide information on as-purchased tow and resin properties and nature of manufacturing process. Micro-CT analysis was employed to measure/evaluate this phenomena non-destructively. Related post-processing parameters namely closed pore number, structure separation, structure thickness and connectivity available in CT-An software are used in order to analyze the microstructure of manufactured composite specimens and their relationship to NCF composite material properties as well as to link these to the anomalies due to manufacturing process within the sample’s mesostructure. The limiting factors and challenges related to micro-CT scanning and 3D image analysis are also presented. Micro-CT analysis results demonstrate that the anomalies regarding resin infusion manufacturing process can be quantitatively evaluated with this NDE technique. The internal micro-structure of composites can be quantified with selected post processing parameters and the ply-by-ply analysis reveal information about the movements of plies during resin-flow based impregnation. These results may lead to further studies where the relationship between stiffness and strength of composite materials and micro-CT analysis outputs could be interrelated