Automotive

Cotton cars to bring down costs of composites

Cotton cars to bring down cost...
A carbon and hemp-fiber reinforced component such as this is a cheaper, greener hybrid composite that can do the job of pure carbon composites(Image: Fraunhofer)
A carbon and hemp-fiber reinforced component such as this is a cheaper, greener hybrid composite that can do the job of pure carbon composites(Image: Fraunhofer)
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A carbon and hemp-fiber reinforced component such as this is a cheaper, greener hybrid composite that can do the job of pure carbon composites(Image: Fraunhofer)
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A carbon and hemp-fiber reinforced component such as this is a cheaper, greener hybrid composite that can do the job of pure carbon composites(Image: Fraunhofer)

Built in East Germany, the Trabant 601 was notorious for its many faults – not the least of which was a body made out of Duroplast, a hard plastic made of cotton waste and phenol resins that led those in the West to describe the car as being made of cardboard. However, it now looks as if the Trabant is getting the last laugh as scientists look at ways of making cars out of cotton and other botanical fibers formed into a new class of hybrid composites.

New emission, safety, and mileage standards in Europe and North America call for vehicles that are ever stronger and lighter, which means that steel and aluminum are giving way to carbon composite materials. Basically, such carbon fiber-reinforced plastics (CFRP) are made up of carbon fibers reinforced by resins, which provides strength and durability, and by tweaking the materials put in, engineers can alter the composite to fit particular applications.

These composites are light, strong, durable, and have proven their worth in everything from F1 racers to aircraft to surgical prostheses, but using them is a trade off. High-tech synthetic carbon composites may be marvelous materials, but they're also expensive and difficult to fabricate. Alternatives, such as glass fiber, can bring down the cost, but they tend to be heavier and not quite as strong.

The Application Center for Wood Fiber Research of the Fraunhofer Institute for Wood Research, the Wilhelm-Klauditz-Institut WKI in Braunschweig is looking into a more natural alternative to CFRPs in natural botanical fiber composites made out of flax, hemp, cotton, or wood. As the Trabant, with its Duroplast cotton composite, shows, the basic idea isn't new, but how Fraunhofer is applying it is.

The botanical composites don't seem like a very good choice at first. They aren't anywhere near as strong or durable as carbon composites, but they are as cheap as glass composites and lighter than glass. In addition, the botanicals burn cleanly without residues.

The clever bit is to take a bio-based textile and carbon fibers and combine them. The idea is not for the botanical fibers to replace carbon, but to supplement them. For example, the strength and durability of a composite panel doesn't need to be the same across the whole unit. Instead, carbon composites can be used in areas that are subject to high strength and wear, while the botanical composites cover other areas. Blending the two together therefore results in a cheaper, greener hybrid composite that can do the job of pure carbon composites.

Once explained, this hybrid composite seems fairly simple, but creating it isn't as straightforward. According to Fraunhofer, botanical fibers are usually made for use in textiles, which means they're treated so they'll run smoothly through spinners, looms, and other textile machines. However, composite engineers want fibers that are treated so they interact with the resins in a manner similar to roughening a wall so it will tightly grip the plaster. In the case of composites, properly treating the fibers can increase a material's durability by 50 percent. Such treatments are routine in carbon fibers, but Fraunhofer says that how to handle botanical fibers is still an unknown.

In addition to this, the Fraunhofer team is also studying how to manufacture the hybrid composites on an industrial scale, how to recycle them, and how to recover the materials in the panels.

Source: Fraunhofer

5 comments
Steve Zanto
Henry Ford worked on this concept decades ago with hemp!
Jim Sadler
Anyone familiar with Micarta which is often used to make knife handles can attest to the strength and durability of cotton or wood fibers or paper fibers pressed together in a resin. There are few limits on what can be mixed and pressed with resins to make sturdy products that can last for many decades.
Ken Tuck
William Randolph Hearst and his ilk are dead. It is time to revive hemp.
Aaron Neilly
This is what the Trabant used in 1957.
Jessica Otero
I prefer HEMP to be honest than cotton. Hemp is far more resistant than cotton and hemp is better for our environment as well. Cotton takes up 50% of the world's pesticide and it takes lucrative amounts of water to maintain it's stability, unlike hemp, which needs no pesticide, and less water. Hemp is softer and more durable than cotton and HEMP car panels are dent resistant. This is why Henry Ford wanted his HEMP car to me made so badly. Plus, hemp helps clean our soil and our air better than cotton. One acre of hemp is equivalent to 20 acres of trees, hemp has a rotation of 4 months, which means that every 4 months it can be cultivated unlike cotton and trees. For those who are worried that people will be getting "high" off of hemp, keep your cool; hemp contains less than 0.03% THC, you would have to smoke 12 hemp trees to start to feel something. Also you can make OVER 50,000 products from hemp, including Bio-Fuel. If the United States grew hemp, they will only have to use 6% of US land to grow this miracle crop to become fully independent from purchasing oil from other countries. Which is something that we should highly consider. Unlike Marijuana, you don't need to separate the female plants from the male plants, everything grows together. I find it odd that the Germans are using cotton when they are already building car panels out of hemp. To be honest, this is a wonderful idea, but to use cotton I see it as a step back instead of forward. By the way, great article!