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Self-Healing Composites
Nick pointed us to this AP story about self-healing composites, fibrous materials with integrated, fungible glue capsules - so that each stress which breaks fibers also breaks the glue capsules to repair those fibers. Very cool stuff, especially if they could make the glue set fast enough to repair in "real time". The Washington Post has another article about the same thing with a bit more detail.
This is somewhat offtopic, but ...
Still further, people often don't realize the extent to which obsolescence is important to the economy - without it, after a few years an industry would become almost obsolete, since all the old equipment would still be in use.
This kind of economy should become obsolent, since it is a waste of resources and does harm to our environment.
By having things break, however, jobs are created,
I'm really tired of this "jobs" argument. If you don't have to buy new things because the old ones do not break, you need less money, thus you can take a part time job without a loss of life-qualitiy, and the number of jobs is preserved.
and improvements are made
I'm very sure, they are made anyway. But these days you have to buy the new things because the old ones breake. With things not breaking, your freedom increases, - your freedom, not to buy.
There are many, many things to do in this world, think of the irrigation of deserts, decreasing hunger and poverty, making software bug-free. - We sure need no industry that relies on things breaking to sell new products.
As someone how works with composites I would like to take this time to point out of few things to the less experienced and therefore point out why a "self-healing" composite of this type is not really that advantageous.
Composites are used mostly because they have superior specific strengths and stiffnesses to more conventional materials like metals. This means that you can make something out of composites do the same job as something out of steel but have it be significantly lighter. This is usually a big advantage.
Composites also have superior fatigue characteristics to most metals. Fatigue occurs because cracks grow in a material as it is loaded cyclicly. Except steel most metals to not have infinite fatigue life. If you have an aluminum bar that takes 10000 lbs to break in one shot, but you load it cyclically at 2000 lbs, eventually this bar will break. Composites don't have much of a problem in fatigue however because cracks end up hitting material interfaces as they try to grow. A crack can only grow so far before it hits a fiber and to move on it has to break this fiber which is pretty difficult. In short if you put a composite sample into a machine to do fatigue tests on it, it is not uncommon for the metal fatigue machine to break before the composite sample does.
Why is all this important? Because this "self-healing" ability is only good for small cracks and it has inferior material properties to a non-healing composite. It helps stop fatigue which is not a big problem in composites anyway. What composites need is a self-healing ability that can cure delaminations and other large scale failures in the composite. This will be important an big news because it is the introduction of large scale problems within a composite that causes the most damage in composites.
So far I've gotten all my Karma from telling people they are wrong... :)
Just think -- self-healing condoms! No longer worry about dying from ripping one of those little bastards.
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Do daemons dream of electric sleep()?
I would think that it would be easy enough to color the repairing resin a contracting color to the original material so that as more and more of it is used the object would slowly change in appearance. This would also help in the inspection/evaluation function to tell when something is weakened too much for continued use
That most of the repairs that this type of material will fix/solve are hidden within the layers of the composite and just weaken the material gradually until a catastrophic failure takes place. I'm sure they'll get the curing time and temperature problems solved now that they have an initial test material to start from. This will be very important in composite propellers and fan blades. It would be interesting to know if you can tell the difference between a fixed and unfixed defect in X-ray inspections.
What happens when you come to demolish the structure? Is this going to be like throwing away a boomerang?
Excuse me if this sounds somewhat foolish, but wouldn't 'real-time' be somewhat useless? A force that is breaking something may be continuous.
Also, this is limited use. Like the articles say, the capsules will eventually be used up. Before this is useful, we'll need to find how much damage this can take (host material, depth, strength, width, number of times?).
We won't be able know how long it will last in a real situation. Testing can only do so much, and we may come to depend on it.
In Nature Magazine.
SIG: TAKE OFF EVERY 'CAPTAIN'!!