Once upon a time all materials were naturally sourced. Now that natural fibers have lost a lot of their traditional market shares to synthetic fibers, they are gearing up to conquer new markets: yarns and fabrics are being tailored to the reinforced plastics industry. Flax is a promising natural fiber. It is relatively stiff and strong. And because it stands out favorably in damping, environmental impact and 3D-capabilities, it is sure to carve out a niche in the composites industry.
“Flax has similar stiffness to glass fiber, but at only half the density,” says Sophie de Rijk, manager automotive of Bcomp (http://www.bcomp.ch/en), an innovative natural fiber company in Fribourg, Switzerland (See Figure 1). De Rijk is a mechanical engineer, specialized in composite materials, and structure, fracture and fluid mechanics. “So, it is superior if you want to make something stiff and light. Carbon fiber is stiffer per weight than flax, but flax has much higher damping than glass or carbon fiber.”
A vibration in a structure made from carbon or glass fiber reinforced polymers will take much longer to dampen out than in a structure made from flax reinforced polymers. So, an important application of flax fibers is to add damping to a structure made of carbon fiber reinforced plastics.
The strength of flax fibers is a bit lower than S-glass, and its price is higher. But as De Rijk explains, it has a lower environmental impact: “The carbon footprint of flax – the embodied energy to produce the raw material – is much lower than of carbon and glass fiber. Also, it does not interfere with food sourcing, but complements it, because flax is typically used as a shifting crop. If your field has to rest for a year, you plant flax. And you do not need water to extract the fibers.”
This article appeared in the May–June 2018 issue of Reinforced Plastics.
