EXPERIMENTAL INVESTIGATION OF TENSILE PROPERTIES OF FLAX FIBRE-REINFORCED COMPOSITES

Renewable materials for aeronautical structures have the potential to contribute to an eco-efficient sustainable aviation. High-performance flax fibres, a promising substitution for glass fibres, are available on the market and currently comprehensively studied. With bio-resins, it is possible to increase the bio-content of composite structures over 50%. However, the mechanical properties of flax fibres are highly influenced by the chosen matrix and process parameters. This paper investigates the tensile properties of composites that are produced from two epoxy, seven bio-epoxy resins and one polyfurfuryl alcohol (PFA) resin in combination with five different flax fibres. It was found that the resin type strongly influences the flax fibre, with PFA inducing a brittle fracture behaviour and lowering the tensile strength for 40.5%, however increasing the stiffness for 17% compared to epoxy matrix. The bundle type of UD sheets and BD weaves are a key factor affecting strength and stiffness with hackled flax, and rovings having the best properties for UD and BD, respectively. Furthermore, the fibre volume content is a crucial parameter influencing mechanical properties, which strongly depends on resin type and production process. Good mechanical properties can be achieved, however with the finding that there is still a great potential for further improvements on the quality and hence the mechanical properties of flax fibre-reinforced composites.