Efficient plant fibre yarn pre-treatment for 3D printed continuous flax fibre/poly(lactic) acid composites

To address the issue of high void contents in 3D printed continuous flax fibre reinforced composites (CFFRCs), an efficient fibre pre-treatment method was proposed to improve the compatibility between plant fibre and resin matrix so that the high-quality manufacturing and excellent mechanical performance were achieved. The surface of flax yarns was treated by silane coupling agents to improve the wettability and interfacial performance. The CFFRCs were then prepared by the customised 3D printing technology, and the mechanical tests were conducted to measure their mechanical properties. It was found that the mechanical properties of the CFFRCs were greatly improved after the treatments which induced very low void contents of less than 1.1%, due to the improved wettability and the interfacial bonding between the flax yarns and resin matrix. The mechanical properties of the CFFRCs prepared by 3D printing in the present work were comparable to those manufactured by compression moulding in literature.