Mechanical properties of flax fibers and their composites

Sammanfattning: Flax fibers, along with a number of other natural fibers, are being considered as an environmentally friendly alternative of synthetic fibers in fiber-reinforced polymer composites. A common feature of natural fibers is a much higher variability of mechanical properties. This necessitates study of the flax fiber strength distribution and efficient experimental methods for its determination. Elementary flax fibers of different gauge lengths are tested by single fiber tension in order to obtain the stress-strain response and strength and failure strain distributions. The applicability of single fiber fragmentation test for flax fiber failure strain and strength characterization is considered. It is shown that fiber fragmentation test can be used to determine the fiber length effect on mean fiber strength and limit strain. Stiffness and strength under uniaxial tension of flax fiber composites with thermoset and thermoplastic polymer matrices are considered. The applicability of rule of mixtures and orientational averaging based models, developed for short fiber composites, to flax reinforced polymers is evaluated.