Mechanical and chemical processes used in the separation of natural fibers for the production of technical fiber based products for composite applications are likely to modify the surface chemistry and the inter and intra-cellular supramolecular structures of the fibers, especially due to the extraction of non-cellulosic components. One might wonder about the influence of these treatments on the resulting physical properties of the fibers and their biocomposites. In this work, we investigated the effect of selective chemical extraction treatments on the biochemical composition and physical chemical properties of flax fabrics, and the microstructure and mechanical behavior of thermo-compressed flax fabrics reinforced epoxy biocomposites. A unidirectional (UD) flax tow woven fabric with minimal processing was chosen in order to retain as much as possible the original flax cell wall structure. The flax fabrics were treated by various aqueous and organic solvents with increasing solvation capacity, so as to gradually extract inter and intra-cellular non-cellulosic components from the fibers. The treated flax fiber fabrics were characterized in terms of biochemical composition, wettability and dimensional characteristics. The influence of chemical extraction treatments on the microstructural and mechanical properties of UD flax/epoxy biocomposites were investigated and discussed by means of Scanning Electron Microscopy (SEM), image analysis, and transverse tensile tests. Our results demonstrate that the extraction of non-cellulosic cell wall components from flax fibers modifies greatly the dispersion of flax yarns within the epoxy matrix, hence generating a higher specific interface area between the fibers and the matrix. The transverse mechanical behavior related to interfacial adhesion is also significantly influenced by the treatments, attesting for the key role of non-cellulosic components in the stress transfer mechanisms from fiber to fiber and fiber to matrix within biocomposites. These results give evidence for the need to tailor plant biomass production and processing for composite applications.

Role of non-cellulosic components on the microstructure and physical properties of natural fibres and their biocomposites

253rd National Meeting (2017)

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