MIT Improves Carbon-Fiber Composites 

In recent years, advanced carbon-fiber composites have been used in planes to make their loads lighter.  These composites have the strength of aluminum and titanium but weigh significantly less.  Most notably, models such as the Boeing 787 and Airbus A380 weigh 20 percent less when using these materials.  

However, researchers are searching for materials that are even stronger and lighter.  Composites made with carbon fibers coated with carbon nanotubes are being considered.  Nanotubes can be hundreds of times stronger than steel and only one-sixth the weight, which is especially appealing for cars, planes, trains and the like.

However, there is still one large problem: when scientists have tried to grow carbon nanotubes on carbon fibers, the strength of these fibers was diminished. 

But in a recent breakthrough, a group from MIT has found out why this happens and has even devised ways to preserve the fibers’ strength.  When they applied their techniques they were able to prevent fiber degradation, thus making the fibers twice as strong.  Researchers say that their methods will not be difficult to integrate into the current fiber-manufacturing procedure. 

Brian Wardle, an associate professor of aeronautics and astronautics at MIT stated, “Up until now, people were basically improving one part of the material but degrading the underlying fiber, and it was a trade-off, you couldn’t get everything you wanted.  With this contribution, you can now get everything you want.”

A group then went to carbon-fiber production plants in Japan, Germany, and Tennessee to get a better understanding of how these fibers were made.  What they found was that most fiber degradation could be attributed to a lack of tension when the carbon fibers were heated above a certain temperature. 

The group then came up with two tactics for growing nanotubes on carbon fiber that would maintain their strength. 

The first tactic involved coating the carbon fiber with a layer of alumina ceramic and then adding a K-PSMA polymer coating to keep the alumina in place.  When the coated fibers were placed under tension, nanotubes with undamaged fibers were effectively developed. 

In the second strategy, the group eliminated the need for tension by dropping the temperature 300 degrees Celsius.  Once again, the fibers were undamaged and the nanotubes were successfully grown. 

Researchers have filed patents for both of the two strategies.

Full story at MIT Media Relations