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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()?
As a post-graduate working on dwindling research grants from the American, Canadian and Australian government, I can only say this breakthrough is really a great relief to both me and my team.
It is my belief that while the interest and funding for our project was thriving in the beginning - our lack of working prototype has really set us back. I can only hope this sets us in the right direction again.
The security level of many areas of our research has steadily decreased from eyes only to 'round'-filed. So I can share atleast a few examples of our failed attempts with you.
But failed almost every stress test:
Many top brass exhibited concerns over human rights issues with our stress-tests; Combining biological matter with computer equipment and our flex-resin technology should orginally have been done with primates (They tell us now!) - but we opted for volunteers; which angered the US officials to no end. In the end, many prototypes were actually taken home by the staff and used as ashtrays
Ace
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
Saving space in the material for glue capsules takes away from the soundness of the material. Why not just put something stronger in the glue's place from the beginning so that the material doesn't break at all?
Another simple composite, concrete, is wellknown long lifespan.
It also self-heals. When it has set, a significant fraction of the material is still unreacted. Microcracks admit water and restart the setting process, reenforcing them somewhat. You can even grind it up and cast it a second time (though the second-cast will be a LOT weaker).
The phenomenon has been known for a while. I wonder if it was the inspiration for this work?
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
I'm reminded of the "Acme Inescapable Rope" used to tie up Roger and Jessica Rabbit.
Think of spider-silk adhesive as the inclusion. Cut it and you end up with the scissors stuck in the rope and the layers of rope bonded to each other, etc.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
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.
>By having things break, however, jobs are >created, and ...
By that logic, we should just cut out the middle man (machines) entirely and have people do all these things the machines are doing. We could create more jobs than we know what to do with.
The idea that something needs to be done in a less than optimal way just to create jobs is the kind of mentality that ran the Soviet Union, not the United States. Wake up! It's the 21st century.
You are in a maze of twisty little passages, all alike.
No mention of how much strength is lost by adding the glue. So, is this going to make the materials more fragile (for the same section/volume/mass)? Anyway retaining 75% of the original strength is no great shakes, especially in safety critical applications.
Frankly, we'd be better coming up with a composite that highlighted damage (glowglue?), rather than trying to paper over the cracks.
If you were blocking sigs, you wouldn't have to read this.
The same goes for fully composite aircraft.
Case in point - the Aerotek / Atlas developed 'ACE' all composite turboprop trainer
(very similar to the Pilatus PC9), had an effectively unlimited fatigue life.
Not too common, though, because very few aerospace mfgs are willing to commit to
pure composite airframes - they merely use composite panels on conventional structures
or complete composite components, such as fins, ailerons, etc.
The only others around are homebuilts, and (with all due respect to their builders),
these are not always the best designed or built structures around!
Ah! there is one notable exception I almost missed: See here
You can even repair a broken pixel in a TFT Flat-Panel display by putting into an oven at 350degrees Fahrenheit. I don't recommend this, of course, because all the other components of your laptop will melt!
In Nature Magazine.
SIG: TAKE OFF EVERY 'CAPTAIN'!!