Flax-based natural composites hierarchically reinforced by cast or printed carbon fibres

Plant-derived natural fibres hold great potential as renewable and sustainable reinforcing elements in structural composites. However, a broader use of fibre composites requires further improvements their mechanical properties, to reach performance comparable carbon fibre-reinforced polymers. In this study, we exploit discontinuous rheologically modified inks controllably reinforce flax-based laminates specific directions. The are incorporated by tape casting or 3D printing approaches directly on the pre-aligned flax structures. With help quasi-static flexural tests dynamic analysis, show that elastic modulus, strength, damping behaviour can be significantly enhanced controlling relative orientation hierarchically structured fibres. stiffness reinforced with oriented along perpendicular increases, respectively, 62% 146% carbon-free reference. This is accompanied 1.6-fold increase loss which indicator for damping. experimentally observed stiffening structures described using simple beam theory. By combining different length scales readily available manufacturing techniques, work shows hierarchical structuring improving