Abstract
Natural fibres are a real opportunity to replace conventional synthetic fibres in composite applications. However, even if they have several advantages in comparison to synthetic fibres (lightness, carbon balance, price…), their moisture sensitivity, their poor compatibility with polymer matrices and their low thermal stability and flammability makes their modification by chemical or physical treatments essential. In this chapter, the multiple and multi-scale interfaces in natural fibre based composites is described. The importance and role of the fibre/matrix interface on mechanical performances and durability, and main strategies to enhance the interfacial adhesion is discussed. Finally, an opening towards new functionalities that could be achieved by fibre and interface modifications is addressed.