On the fatigue and impact resistance of fibre-metal-laminates reinforced with flax fibres

The need to develop new lightweight and environmentally-sustainable materials has led to an increased interest in biofibre-reinforced polymer composites. However, these composites alone do not possess sufficient mechanical properties required for structural applications. In an attempt to harness the environmental sustainability of natural fibres while achieving mechanical properties comparable to conventional lightweight structural composites such as fibreglass, flax-reinforced polymer laminates were hybridized with aluminum alloy sheets to create novel biofibre-reinforced Fibre-Metal-Laminates. This study evaluated the tension-tension fatigue and impact performance and explored the associated damage evolution in the flax-reinforced FML composites. For bench-marking purposes, the fatigue performance and impact resistance of the flax-reinforced FMLs were compared to those of counterparts reinforced by glass fibres. Flax-reinforced FMLs retained their stiffness and dimensional properties throughout the fatigue lifetime while glass-reinforced FMLs suffered significant reductions in both of these parameters. When the applied fatigue strength was normalized with respect to material density, the fatigue performance of flax- and glass-reinforced FMLs were comparable. At low impact velocities, the impact performance of flax- and glass-reinforced FMLs were comparable. However, under elevated impact energies, the glass-reinforced FMLs were superior to their flax counterparts. Research findings reported in this paper demonstrate the feasibility of adapting flax-reinforced composites into fatigue-critical and impact damage resilient engineering structures for the rail and automotive industry.