Identifying microstructural features in unidirectional composite tapes

Carbon fibre-reinforced polymer composites (CFRPs) outperform most structural engineering materials in specific stiffness and/or specific strength, especially in their unidirectional configuration. Unidirectional composites can be found as individual structural elements in cables or pin-loaded straps; they are however most commonly found in the form of tapes, representing a semi-finished product for subsequent processing to laminates by tape laying, winding or press moulding. The outstanding properties of such composites are affected by its microstructure. It influences the structural performance and fatigue life when architected into thin ply composites [1]. The microstructure is also affected by processing conditions, respectively recursively affects processability as observed in the deconsolidation [2] or intimate contact formation [3] during laser assisted tape laying. This work presents a novel approach to identify microstructural features. This is achieved by Voronoi tessellation-based evaluation of the fibre volume content on cross-sectional micrographs, with consideration of the matrix boundary. The method [4] is shown to be robust and is suitable to be automated and has the potential to be expanded into 3d imaging techniques [5]. It further has the potential to discriminate specific microstructural features and to relate them to processing behaviour. The method is experimentally validated on tape samples with characteristic processing history.