I’m going to talk a little more about natural fibers and resins – natural strings and glues – because there are large strides that have been made and that are being made in development of commercially available bio-based strings and glues. And yes, there’s a picture of a windmill here, but the story is far more than just the windmill, it is the field of natural fiber that the guy is standing in that I am going to focus on here.
There is an interesting article in the March 27 issue of Composites World that is sort of the inspiration for this post (https://www.compositesworld.com/articles/natural-fiber-composites-growing-to-fit-sustainability-needs). What the article talks about is one facet of what I want to touch on in this post – the growing use of natural fibers in composites in high performance and high volume applications.
I’ve talked a bit about natural fibers and plant derived resins in newsletters prior to this one, but what I had not really delved into is the increasing use of fibers from flax, hemp, and bamboo that are finding their way out of niche markets into the mainstream. This is driven partly by the perceived need to pivot to a sustainable model for composite materials, and partly by newer environmental regulations – particularly in Europe – to move away from petroleum based precursors for nearly all industrial products.
The reticence in the past with regard to adoption of natural fibers in particular was due partly to the non-uniform nature or varying fiber quality and performance of plant based fibers. In the last 10 years or so, several University researchers have developed surface modification techniques and fiber manufacturing techniques that have significantly improved the overall performance of natural fibers in composites.
The real stars of this new revolution in natural fiber composites are flax and hemp fiber (the two pics above). Widely cultivated in Europe (mostly France) and Canada, both plant fibers have in the last 3-5 years seen tremendous expansion into markets that are price sensitive, weight sensitive, and also vibration and noise sensitive. The automobile market is the best example of this, where flax fiber is used by nearly every major automotive manufacturer in their new car production. This is not just for interior fabrics; it is also for noise damping and vibration control.
These fibers are also being incorporated in to composites where the glue (resin) is at least partially if not completely plant-derived. In fact, according to the article in Composites World, one of the largest resin suppliers, Hexcel (Stamford, CT), has launched a new range of plant derived composites they call their “HexPly Nature” range of composites which consists of woven and stitched flax fiber reinforcements with HexPly M49, M79-LT, and M79.1LT epoxies which contain partially bio-derived content.
In addition to Hexcel, Porcher Industries (France) and Saertex (Germany) have also introduced flax fiber composites using flax from Terre do Lin in France. This company claims to produce 15% of the worldwide production of flax, and they are probably correct, since they are the largest flax producer in France.
And there is another company in San Francisco – Lingrove – that has launched a flax fiber and plant based resin product that mimics wood. The product they produce, which they call ekoa (image to the left), is used to replace wood in ukeles and guitars, sproting goods, and finally into automotive interiors. The automotive market has adopted this material because it makes a fully recyclable, natural fiber/resin replacement for wood in things like dashboards and glove box doors that does not need the maintenance of wood, and does not require cutting down trees.
The real things holding back full adoption of these materials into advanced composites I touched on in a previous post, but they bear repeating here. Fiber of high enough quality and consistency that it can be relied upon for a high volume application has only just recently become a reality. There are also processing issues with natural fibers and their ability to soak up resins. Plant fibers are very porous, so they tend to sponge up the resin and it is difficult to control the fiber/matrix percentage in a final product. Wet layup – the most common method of making composites – is not appropriate for natural fibers because of the inability to control resin content. Instead, vacuum molding, RTM, Vacuum Assisted RTM, and processes like these are required. So, making something in quantity using these fibers requires some capital expenditure. But, high volume production always does require capital investment, so this particular burden is being overcome rather well by manufacturers that start with the intent of using plant based composite precursors.
As you can see, plant based fibers and resins have come a long way in the last 10 years or so, and are poised on the precipice of becoming mainstream. Fabricators, manufacturers, fiber suppliers, resin suppliers, have all been working diligently in the last 10 years to develop processes and equipment that will support high volume and high quality, repeatable composite parts.
Finally, now that I am a licensed Professional Engineer in the State of California, I created an engineering consulting company - Patton Engineering and Consulting - to take advantage of the license, and to help people solve problems, and to design, analyze, and build things using composites for customers that need that service. If you have a good idea, just send me a message and let's talk. My email address is ned.patton@gmail.com.
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