Influence of the flax fibre chemical composition on mechanical properties of epoxy biocomposite

Abstract : Natural fibres based composites are increasingly used mainly because of their low density and positive life cycle assessment. Nevertheless an improvement of their mechanical properties is required. A better control of i) the fibre/matrix interface and ii) the intra-fibrillar interface within the fibre bundles (composed of cellulose micro-fibrils, hemicelluloses, lignins, pectins and lipophilic extractives) has to be established. The aim of this study is to investigate the influence of different flax treatments (among them water, alcohol, surfactant, alkaline treatments) known to remove selectively flax fibre components, and their effect on flax fabrics properties and on interfacial behaviour of flax/epoxy biocomposites. Components removal was evaluated by chemical composition and FTIR. Mechanical tests and SEM observations were used to study the composite interface. A defibrillation phenomenon within the fibre bundles was responsible for a significant decrease of the biocomposite transverse strength whereas the porosity was reduced for all the treatments used.