Compressive behaviour of unidirectional flax fibre reinforced composites

The compressive strength of unidirectional flax fibre epoxy composites was studied. The compressive strength is influenced negatively by the presence of kink bands in the flax fibres. Improvement of the adhesion between the fibres and the epoxy resin can be achieved easily by removing the thin wax layer which covers the surface of the flax fibres. However, improving the adhesion between fibres and matrix only improves the compressive strength to a very limited extent. Stabilisation of the kink bands present in the fibres and improvement of the compressive properties of the fibres can be achieved by impregnating the fibres with melamine formaldehyde (MF) resin. This results in a large increase in the compressive strength of the resulting composite. The increase in compressive strength is proportional to the amount of MF resin present in the composite. However, the presence of the resin in the fibres lowers their tensile strength, and subsequently the tensile strength of the resulting composite.