Mechanical characterisation and interfacial analysis of continuous flax fibre reinforced unidirectional green composites using filament winding

Plant fibre-reinforced biobased thermoplastics (also known as “green composites”) are interesting materials from the point of view of eco-sustainability but still have problems of lower mechanical properties and difficult processability when compared to other more common composite materials, such as continuous glass or carbon fibre-reinforced thermosets. In this paper, unidirectional green composite laminae made of flax fibre-reinforced polylactide (PLA) were obtained through film stacking together with a filament winding process followed by a hot compaction phase. This technique permits to apply pretensioning on the flax rovings before hot compaction to limit possible misalignment. Interfacial properties measurement, analysis of fracture surfaces and a complete tensile mechanical characterisation were performed to evaluate the effectiveness of this procedure. The results showed that a structural composite in the longitudinal direction (∼170 MPa strength) can be obtained that has a low void content, an adequate fibre–matrix macro-impregnation and a limited dispersion in mechanical properties due to the limited fibre misalignment.