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article imageSelf repairing carbon fibre works, so nothing may be the same again

By Paul Wallis     Oct 8, 2007 in Science
Science fiction fans will remember self repairing machines from a few shows. It’s so simple you’d scream, but it’s good science by any standards. Using carbon nanotubes, structural strength and integrity in composite materials can be increased.
The nanotubes can also help detect fractures and repair themselves.
Try this for simple:
“By infusing a polymer with electrically conductive carbon nanotubes, and then monitoring the structure’s electrical resistance, the researchers were able to pinpoint the location and length of a stress-induced crack in a composite structure. Once a crack is located, engineers can then send a short electrical charge to the area in order to heat up the carbon nanotubes and in turn melt an embedded healing agent that will flow into and seal the crack with a 70 percent recovery in strength.”
It’s a really beautiful idea.
Resistance is why light globes glow, and why they get hot. It's a great targeting method.
The researchers at Rensselaer Polytechnic Institute (extremely interesting site, don't miss) are aiming high enough. One of the possible applications for the new technique is in aircraft wings. That’s impressive, because the loads on aircraft wings are enormous. They’re stressed to extremely high standards, and this idea should be a dream come true to besieged aircraft maintenance, where fatigue is an ongoing nightmare, and costing a fortune, globally.
According to Rensselaer, fatigue is started by micro-cracks, which by definition aren’t easy to find. Currently ultrasound is used to detect them. The joy of this method is that monitoring of materials can now be done in real time. Cracks show up as increased resistance in the composite, meaning detection is inevitable, and instant.
The 70% recovery is considered adequate to prevent catastrophic failures, but it’s a fairly safe bet that the technique will improve beyond that. This is a very important development in polymer science. Carbon nanotubes are becoming the staple of new composites, and they’re bringing a lot of new ideas and science with them.
The possibilities are huge. Regeneration of materials, particularly structural materials, has a lot going for it. Houses using polymers would be easy to maintain. Vehicles, too. A lot of cost is tied up in dealing with materials which just fall to bits.
That "planned falling to bits" used to be a sort of Machiavellian thing in domestic products, too. Now it’s just a pain in the pocketbook. Replacing the entire contents of households is an ongoing process, and it cuts into quality of life, because it’s so expensive. Clothes, domestic appliances, paintwork, in fact most of the retail dream, routinely fall to pieces. Product life has been getting shorter, and contrary to the idea that it means people will buy more things, it’s turned out to mean that people won’t buy unless they have to, because they don’t trust the quality any more, and repairs are incredibly costly. Nobody's winning the cost war, and the idea has now outlived its expiry date by at least 30 years.
So now, the Repair Anything Kit of the future. You can find a problem, at micro fault stage, before it gets lethal, and repair it. Regrow your house or your socks.
The monitoring idea is also extremely important. That idea alone is heading into Nobel Prize territory, and could go a lot further. The world has suffered a lot from shoddy materials, particularly in synthetics, and if all it takes to get decent quality and product life is a 1% mix of nanotubes, everybody in manufacturing, from the process line to retailers to recycling, stands to gain.
Products could be monitored at molecular level. Things like lead paint, or other unwanted materials, would play havoc with resistance levels. Passing a low level electrical charge through some foods would be an excellent testing method, because many fertilizers, pesticides and other harmful chemicals are electrically active.
Everything has some form of electrical resistance, and those can be calibrated. You’d know what the contaminant was. Think of it as spectography with electricity. If that’s possible, industrial testing just got a lot simpler, cheaper, and much easier to manage around the clock. That will save producers and consumers a fortune.
Rensselaer may have just found the answer to a lot of the world’s most annoying, persistent, problems, and opened up a whole new science, with these ideas.
If this takes hold, nothing will be the same again. The world's economics will change, and the Nano Age will have begun.
More about Carbon nanotubes, Rensselaer polytechnic institute, Polymer science
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