Single fibre characterization of heavily curved polymer fibres using X-ray computed tomography

The material system polypropylene filled with long polyethylene terephthalate fibres was investigated by CT analyses. Micro-structural features as length, orientation, diameter and content were determined comprehensively. Beside the characterisation of an undamaged multi purpose test specimen (MPS) a broken Charpy impact tested specimen was analysed, too. The fibres that were pulled out of the matrix were segmented and analysed separately in order to determine the free fibre length. The extraction of relevant features was performed on single fibre basis with a template matching apporoach for medial axes extraction. The following image processing steps for separating and connecting fibre segments correctly were optimized for the heavily curved polymer fibres. Together with a micro-structural characterisation of undamaged MPS specimens, valuable data for understanding the influences of fibre length, orientation and complex pathway on mechanical behaviour was generated. The high amount of curved fibres together with the difference of Euclidian and curved average lengths make it obvious that the consideration of PET fibres as curved is essential for modelling the real material behaviour with the determined micro-structural values.