Internal structure and fatigue performance of quasi-unidirectional Non-Crimp Fabric reinforced laminates

The aim of this work was to study the effect of stitch pattern and stitch tension on tension-tension fatigue performance of quasi-unidirectional non-crimp fabric reinforced glass-fibre/epoxy laminates. Internal structure variations of the laminates were characterised using cross-sectional microscopy imaging for the evaluation of fatigue test results. Reinforcements for the study were manufactured with three different stitch patterns and two different stitch tensions. Based on the results, the stitch pattern contributes in-plane and out-of-plane waviness of fibres, as well as on the size and shape of the axial fibre bundles. The fatigue life and slope parameter of the fitted S-N curve were significantly dependent on the stitch pattern while they were not dependent on the applied stitch tension.