Influence of processing and chemical treatment of flax fibres on their composites

During the consecutive decortication stages of flax fibres (retting, scutching, hackling, …), the fibre properties change tremendously due to mechanical and chemical modifications. This study points out the influence of the flax processing parameters, and consequently of the fibre properties, on the mechanical properties of flax fibre reinforced epoxy composites. The better the retting degree of the fibres, the better the composite properties are. The use of long flax slivers does not necessarily result in better composite properties. The influence of certain chemical treatments, performed on the flax fibres, on the composite properties has been studied as well. Treatments with alkali, dilute epoxy, acetone and silane were carried out. A treatment consisting of a combination of alkali and dilute epoxy gives the highest improvement of the flexural properties. The longitudinal properties of the UD composites (both strength and modulus) enhanced with 40% or more, transverse strength increased with 250%, transverse modulus could improve up to 500%.