Winter flax: Stem structure, fibre properties and reinforcement potential for composite materials

Climate change is characterized by rising temperatures and an increased risk of spring water deficit, both of which threaten the cultivation of textile flax. With the multiplication and intensification of these phenomena, fibre plant yields have become increasingly uncertain in recent years, leading to shorter stems as well as reduced yields. In this context, winter flax cultivation emerges as a solution to sustain the exploitation of this plant. Sown before winter, it can resist periods of spring water stress, owing to the early development of it root system, and is also protected from the summer heat. In this study, we investigate the stem architecture and fibres properties of two winter flax varieties, in comparison to spring flax. Cross -sections reveal that both winter and spring flax have a similar plant structure. The part located at mid -height of the winter stem contains the most fibres, accounting for around 23% of the biomass. At the middle of the stem, the elementary fibres of the Cirrus and Olga varieties have an average length of 20.9 +/- 7.7 mm and 30.0 +/- 10.8 mm, respectively. At this same plant height, winter flax fibres of the Cirrus and Olga varieties have an average Young 's modulus of 63.6 +/- 18.8 GPa and 57.6 +/- 20.8 GPa, and an average strength at break of 1248 +/- 554 MPa and 1187 +/- 627 MPa, respectively. As a conclusion, winter flax has a similar length and mechanical properties to spring flax and therefore offers the same potential for textile applications. In addition, as demonstrated in this study, winter flax can be similarly useful as a reinforcement in composite materials.