Variable angle tow composites in fibre-reinforced polymer bridges

Fibre reinforced polymers are increasingly used in bridge structures for reducing their environmental impact, extending the service life and saving costs. In this work, we propose the use of composite laminates called Variable Angle Tow (VAT) to realise bridge structures. In VAT composite laminates, the fibre orientation changes pointwise over the structure, enhancing stiffness tailoring capabilities with respect to traditional straight fibre (SF) laminates. In aerospace engineering, VAT composites have been successfully used to tailor structures’ stiffness to enhance linear elastic response, reduce buckling phenomena, and optimise the postbuckling behaviour. However, VAT laminates have never been applied in civil structures. This work shows how using VAT composite laminates in a bridge girder improves its buckling and postbuckling behaviours and increases its overall stiffness. A numerical investigation is conducted to assess the benefits given by VAT composite laminates to the structural performance of bridge girders. For different spans, results of a multi-objective optimisation considering both traditional SF and VAT laminates are presented. It is found that VAT laminates exhibit a buckling load up to 80% over SF laminates, with equal or lower deflections and without adding extra material, thereby opening new design scenarios for bridge structures.