A multi-scale study of the interface between natural fibres and a biopolymer

A significant recent development in the composite field is the appearance of biocomposites (biopolymers reinforced by plant fibres) which combine mechanical performance and low environmental impacts. However, to replace conventional composites a significant effort is needed to understand their mechanical behaviour under complex loading (both in-plane and out-of-plane). The interfacial behaviour (fibre/matrix) of these materials also requires particular attention in order to optimize mechanical properties. With this aim modified Arcan, transverse tension and microdroplet debonding tests have been performed on flax reinforced PLLA biocomposites, as very few data of this type are available.The out-of-plane tensile and tensile–shear properties of these biocomposites are lower than those measured in shear. Manufacturing parameters, and particularly consolidation pressure, are critical for these materials. Out-of plane apparent shear strengths are similar to those from debonding tests. A common feature of the tests performed at the three scales is the appearance of fibre peeling.