Role of flax cell wall components on the microstructure and transverse mechanical behaviour of flax fabrics reinforced epoxy biocomposites

• Flax tow fabrics were treated by solvents with increasing solvation capacity.
• Chemical and FTIR analysis reveal a gradual removal of flax cell wall components.
• Microstructure of flax/epoxy composites is greatly modified by the chemical treatments.
• Removal of flax cell wall components affects transverse mechanical behaviour of composites.

Mechanical and chemical processes used in the extraction of flax fibres for the production of technical flax fabrics and other flax products have a significant effect on their biochemical composition, structure and properties. In this work, we investigated the effect of different chemical extraction treatments on the biochemical composition and physical chemical properties of flax fabrics and their influence on the microstructure and mechanical properties of thermo-compressed flax fabrics reinforced epoxy composites. A unidirectional (UD) flax tow woven fabric with minimal processing was chosen in order to retain as much of the original flax cell wall structure as possible. The flax fabric was treated by various aqueous and organic solvents with increasing solvation capacity, so as to gradually extract cell wall components from the fibres. The treated flax fibre fabrics were characterised in terms of biochemical composition, wettability and dimensional characteristics. The influence of chemical extraction treatments and the role of cell wall components on the microstructural and mechanical properties of UD flax/epoxy biocomposites were investigated and discussed by means of Scanning Electron Microscopy (SEM), image analysis, Differential Scanning Calorimetry (DSC) and transverse tensile tests. Our results demonstrate that non-cellulosic cell wall components of flax fibres play a key role in the dispersion of flax yarns within the epoxy matrix, and in the mechanical behaviour of biocomposites.