Optimisation of crush energy absorption of non-crimp fabric laminates by through-thickness stitching

Through-thickness stitching has been used to significantly improve the Mode-I interlaminar fracture toughness properties, however these improvements do not always translate positively to the crushing properties as there are many parameters that could influence the energy absorbed. The current research was therefore undertaken to understand the relationship between stitching of non-crimp fabrics (NCFs) and the resultant effects on energy absorption during crushing. A design of experiments (DOE) technique based upon the Taguchi method was utilised to statistically determine the relationship and assist in optimising the crushing properties. The laminates were flat plates manufactured from carbon- and glass–fibre NCFs; stitching was carried out with carbon and Kevlar threads in different configurations, and the laminates were vacuum infused with vinyl-ester and epoxy resins. The results show that by selecting an optimised stitching configuration, an improvement of 30% in the energy absorption can be achieved.