# Morphological modification of the technical flax fibre bundles to improve the longitudinal tensile properties of flax fibre reinforced epoxy composites

**Authors:** Rishad Rayyaan, William Richard Kennon, Prasad Potluri, Mahmudul Akonda  
**arXiv:** [1803.03366](https://arxiv.org/abs/1803.03366)  
**Date:** 2018-03-09  
**Summary page:** https://www.summarizepaper.com/en/paper/1803.03366v2/

## Key points

- Flax fibers are excellent reinforcements for composites
- Conventional textile methods result in damages that degrade the mechanical performance of flax fiber reinforced composites (FFRC)
- Fiber undulation or waviness is a damaging feature that leads to micro compressive defects or kink bands in flax fibers
- Researchers developed a novel technique to manufacture flax fabric with minimal undulation
- Nonwoven flax tapes consisting of highly aligned fibers blended with PLA were created as reinforcements for composite materials
- Mechanical tests showed significant improvements in fiber bundle strength and stiffness for composites reinforced with highly aligned tape compared to Hopsack fabric
- The improvements can be attributed to factors such as reduced fiber undulation, enhanced elementary fiber individualization, improved homogeneity of fiber distribution, minimized resin-rich areas, and better impregnation of the fiber lumens
- Minimizing fiber undulation in flax fabric manufacturing enhances the mechanical properties of FFRC
- Nonwoven flax tapes with highly aligned fibers blended with PLA offer a promising solution for improving the longitudinal tensile properties of FFRC.

## Summary

Flax fibers are known for their excellent tensile properties and are considered one of the top-end reinforcements for composites. However, conventional textile methods used to process flax often result in damages that degrade the mechanical performance of FFRC. One such damaging feature is fiber undulation or waviness, which leads to micro compressive defects or kink bands in elementary flax fibers. To address this issue, the researchers aimed to manufacture flax fabric with minimal undulation by developing a novel technique. They created nonwoven flax tapes consisting of highly aligned fibers blended with a small proportion of PLA. These nonwoven tapes were then used as reinforcements for composite materials. To evaluate the effectiveness of these nonwoven tapes compared to traditional woven Hopsack fabrics and warp knitted unidirectional (UD) fabrics made from undulating fibers, various mechanical tests were conducted. The results showed that composites reinforced with highly aligned tape exhibited significant improvements in fiber bundle strength and stiffness compared to those reinforced with Hopsack fabric. Specifically, the composites reinforced with highly aligned tape demonstrated a 49 percent higher fiber bundle strength and a 100 percent higher fiber bundle stiffness compared to the Hopsack fabric reinforced composites. These improvements can be attributed to factors such as reduced fiber undulation, enhanced elementary fiber individualization, improved homogeneity of fiber distribution, minimized resin-rich areas, and better impregnation of the fiber lumens. Overall, this research highlights the importance of minimizing fiber undulation in flax fabric manufacturing to enhance the mechanical properties of FFRC. The use of nonwoven flax tapes with highly aligned fibers blended with PLA offers a promising solution for improving the longitudinal tensile properties of flax fiber reinforced epoxy composites.