Forgot your password?
typodupeerror
Science

Self-Healing Composites 103

Posted by michael
from the not-quite-as-good-as-R2-D2 dept.
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This discussion has been archived. No new comments can be posted.

Self-Healing Composites

Comments Filter:
  • >A self-healing material sounds marvellous, but the fact is, as in real life, things need to
    >break, as part of the natural cycle - if not, there is a potentially greater risk to us.

    You're assuming that the material will wear out more slowly. In some cases that may happen, but in many cases it won't- a lot of wearing out is caused by surface effects, and the glue won't help there much.

    This technology mainly reduces the chance that the part will catastophically fail- it will not usually increase the life; but it may increase the production yield, which tends to cut product costs without materially affecting manpower levels.
  • So...what I assume is that this is the first crude steps towards true self-healing materials. Potentially in the future, we could be driving cars that are filled with some chemicals that scab and repair the body underneath just like our skin does. That would be really good and I'm glad we are making the first steps towards that.

    Of course, with the great strides we are making with placing computers in cars and crude AI systems, how long will it be before our car says, "Daddy, I have a booboo on my tailpipe. Can you kiss it and make it better?"

  • by gerddie (173963) on Thursday February 15, 2001 @03:14AM (#430536)
    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.
  • A brilliant suggestion! I only wish I had mod points to share with you.

    John

  • Fungible is a great word. I particularly like to hear it in business discussions.

    CEO: Are these budget numbers hard?

    VP of Finance: No. The deadline isn't until next Thursday, so they are fungible.

    CEO: Well, I think we should try Desotin.

  • I was actually reading "Appleseed" an old manga by Masamune Shirow that mentioned self-healing polymers on a motorcycle fairing. In the comic it said "You have to use a special wax of course." I think its funny to see something that's science fiction actually become science fact within your lifetime.
  • The idea of embedded glue as a composite repair mechanism has been around since the '60s (Courtaulds, UK, in reference to some early carbon fibre laminates, back when the UK had an aerospace industry).

    The tricky aspect is that most cure mechanisms also involve a volume change. Get it right and you glue the crack shut. Get it wrong and you've driven a wedge in to make it bigger.

    Of course in your meteorite shield, the macroscopic strength (structural) is less important than the microscopic scale (impact resistance), so the idea could still work well.

  • Over the past 4 years there was a composite that was basically a sandwiched layer with a resin that was water activated. if the hull cracked or was damaged the resin flowed in and solidified in minutes due to a reaction with the water. It's not back to 100% strength but it was enough to get you home.

    I believe that the sailing yatcht playstation has this technology.
  • They'll be great things for our landfills.
  • by Life Blood (100124) on Thursday February 15, 2001 @06:38AM (#430543) Homepage

    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.

  • I think it would be more-fit to call it self-repairing, or self-glueing. I think self-healing would be something more organic, and that would heal back to %100 strength. That, would probably be close to impossible. To the best of my knowledge, you can't break something (for ex a piece of glass), and put it back EXACTLY, molecular-bond to molecular-bond the same as it was before. For now, the only thing they will be able to do is just repair it. Now, what they could do is just set it up so that when it is repaired, it is stronger than what it was previously, and as one stated before, colored. That way you knew where the problem occured. When somoeone breaks a bone in their body, and, if it heals, it isn't weaker than what it was before, it is stronger. This could be close to teh same concept, but again, right now, it's not organic...
    You know you want to click me! :) [rackshack-affiliates.net]


    I know, I know, I know; posting on slashdot isn't supposed to = free advertising. Oops...
  • Haven't tires been doing this for 20 years?
  • by multipartmixed (163409) on Thursday February 15, 2001 @05:04AM (#430546) Homepage
    Just think -- self-healing condoms! No longer worry about dying from ripping one of those little bastards.

    --
  • here is the article on the bbc: http://news.bbc.co.uk/hi/english/sci/tech/newsid_1 170000/1170304.stm
  • Well, I think you'd be hard pressed to find a Corvette with a worn-out body, proving it hasnt been in an accident.
    As a car collector, I've have seen various stages of neglected vette's, but the fiberglass is always fine, even if they had been sitting out for 25+ years
    Frame and floorpan might be gone, burt the bodies still there ;oP

    -Caino

    Don't touch my .sig there!

  • Way to go U of I!!! Just read about this in our local newspaper... pretty cool stuff.
  • by jjr (6873)
    SpiderGoat-Silk you can have a substance that can take a real licking and keep on ticking
  • by Anonymous Coward
    It seems to me that if you bent the structure and then kept it bent while the glue capsules set, it would pemanently change the shape of the structure. So it you had constant stress (I'm thinking aircraft wings bow under the weight of the fuselage), the shape changes. Bad.... Of course, maybe you could use this to make small adjustments to the shape of things when you're putting them in place?
  • making software bug-free. - We sure need no industry that relies on things breaking to sell new products.

    *cough* Microsoft *cough*

  • 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?

    I hope you aren't a structural engineer. It seems obvious to me that lattices are going be be stronger against some kinds of stress than solid blocks. A material that needs to be able to tolerate some amount of tourque (sp?) or provide flexibility (like the joints of a space suit) or that by design you would rather have develope small cracks that heal rather than hold inflexible until it shattered (rails, perhaps?) is going to have the potential for improvement by this process.

    rigidity and strength are not always synonymous. Nor, for that matter are absolute strength and suitablity for a job.

    Kahuna Burger

  • Yes, you're right. Yes, that goes at least as far back as Henry Ford, but you're also right that it's for a completely different reason.

    There's nothing wrong with a company selling products that are planned to fail after a certain time, because another company can come along and sell one that won't. If you're the kind of person who wants to keep something a long time, you can usually find a product that will last longer... of course it might cost a little more.

    That's why I buy Hondas. I plan to drive my one-year-old off to college in the Odyssey I have now.

  • by TShark (69724)
    Why not just make stronger fibers?
  • I read about this last night, the point isn't to make stuff that will last longer under normal use per se, the main point seems to be to make construction materials that will try to hold themselves together a little longer than normal. The example that was used was the concrete in an apartment building, if it was made with a "self-healing" material then in the case of catastrophic damage (like an earthquake) it could conceivably give people a little more time to evacuate the structure before it collapsed. The trick to me seems to be to NOT tell people about it, that way they will evacuate like they have no time instead of trying to save their tv/stereo/cd collection/box (I know, foul blasphemy to mention "the box" as less valuable than a life!!!)
  • This is reminiscent of a technology that goes back quite a ways.
    A porous cemented-fiber composite is impregnated with a monomer/catalyst mixture.
    The monomer polymerizes to a weak solid in presence of the catalyst (which adheres to the fibers) to strengthen the composite, and in case of a fracture, the liquid monomer wicks to the newly created surfaces and both straightens the fibers (by surface tension) and fills the gaps.

    Now a little shift of viewpoint; the porous cemented-fiber composite is 'wood', the monomer/catalyst mixture is 'boiled linseed oil', and the fracture scenario is 'scratch the finish and a few hours later the scratch heals up'.

    This variant of the technology goes back a few
    years. :-)
  • Why would we suddenly start keeping obsolete equipment? Companies don't throw out broken equipment, they throw out broken OR OBSOLETE equipment. Lately I have had to throw out several computers, not because they are broken- but because they were old 486's without monitors or NICs and aren't worth anything. My boss's car (company owned) is probably also going to be replaced, not because it's damage beyond repair, but because the cost to repair is more than a new car would be.
  • by Ace905 (163071) on Thursday February 15, 2001 @03:17AM (#430559) Homepage
    The idea for a material of this nature has been kicking around since well before the 80s, but at the time - the technology just wasn't available.

    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.
    1. Our first prototype showed promise [ifi.uio.no]
      But failed almost every stress test:
    2. System overloads under nominal thermal stress [ifi.uio.no]
    3. Prototype A11H1.1 [ifi.uio.no]
    4. Prototype A13L4 [ifi.uio.no]
    5. Prototype operator fatality [ifi.uio.no]

      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 [ifi.uio.no]
  • Corvettes that don't get worn out? I don't think the car industry would allow that.

    Nobody likes to have their product-cycles prolonged.

  • First let me state that i do not agree with the concept of built-in obsolescence.

    As i see it, i buy things (say a TV) to use them for personal gain (easier work, entertainment, aestetic pleasure), not to stimulate the economy. If a new product comes out with an improvement that i consider worth my hard earned bucks (for TVs: color TV; remote control; 3D imagery) i will buy a new one. Otherwise i'll stick to the old one (why ditch my money for a new TV just because it now comes in a semi-transparent purple plastic model???). Actualy, durability is one of my top criteria when buying new equipment.

    Beyond this, there's also the fact that a whole class of things cannot have built-in obsolescence:

    "Ladies and gentleman, this is the captain. I regret to inform you that our airplane has reached it's built-in obsolescence deadline of 10 years. The engines are falling-off so we will have a slight delay."

  • If it wasn't for the 75%-of-the-original's-strength angle, this would be life imitating art. Does anyone else remember "The Man in the White Suit"? It's an old Alec Guiness movie in which Alec plays a young textile whiz who invents the perfect material for use in clothing.

    The crux of the movie is that he develops this suit made from his amazing textile -- it needs no washing or ironing, it lasts forever -- and of course the powers that be in the clothing industry immediately see why they need to kill him and bury the suit, literally. Lots of fun gets poked at modern consumer culture; it's just the sort of movie that got made during the U.K. Labor years after WWII.

  • is it going to be enough resin to fix the object two, three, twenty times?

    it appears to me that they are only going to delay an event....
  • by coreman (8656) on Thursday February 15, 2001 @03:36AM (#430564) Homepage
    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
  • This is similar to an idea, some fiends and I played around with at Univerity. I admit we stole the idea from canoeist/kayekers, who use two part foam for wilderness repairs. The idea was for self healing hull's to protect space craft from micro-meteors.

    The best way to describe it is layers of "bubble wrap", alternating with layers of woven Carbon-Kevlar, the bubble's in the bubble wrap would contain a binary (two part) foam or resin. When the two or more 'bubble wrap' layers are breeched the binary components interacts and forms foam or resin, which cloggs up the fissues or holes.

  • I compete in composite R/C gliders. This has a real effect on my life and knowing how much something has used up the healing part of the mix would be somewhat important. Hell, I'd settle for something that changes color due to stressing so we're be better able to detect stress point areas
  • Of course they are only delaying it. But any delay means an increased lifetime for the object, and if the delay is, say 10% of the original lifetime, and costs less than 10% more, then it's worth it.
  • Sorry I don't have any mod points. Very funny
  • Near real time would be useful but, as seen with superglue, you need a bit of time before you want it to heal. Keep in mind that the stress crack will open and separate and you want the reair to happen aftre the stress cycle so the repair is in the unstressed position. We don't need a material whee the stress cracks fill in and hold the material in the stressed position
  • by webrunner (108849)
    Well it's good to know that Science is getting all the physical stuff out of the way BEFORE making AI, so any rouge AI can just build a robot made out of self-repairing laser-deflecting EMP-proof armor.
    ----
  • by Davace (250100) on Thursday February 15, 2001 @05:24AM (#430571) Homepage
    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?
  • by Ungrounded Lightning (62228) on Thursday February 15, 2001 @05:27AM (#430572) Journal
    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?
  • In many cases this isn't possible. Most materials balance strength/flexibility/hardness. Anything that flexes will result in stress failures over time. If you can create a substance that has the same physical properties as your current polymer, but lasts longer, that is a notable achievement.

    Sometimes it just isn't possible (or desirable) to make something firmer. ("put something stronger...") Doing so will just lead to an earlier failure in many applications.
  • by Ungrounded Lightning (62228) on Thursday February 15, 2001 @05:35AM (#430574) Journal
    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.
  • I think the overall structure of breakwater could be considered "self healing" although in a different sense than the article. Just because the constituent pieces are macro- rather than micro-size doesn't mean that some interesting (and strengthening) adjustment isn't taking place.

  • Just think -- self-healing condoms! No longer worry about dying from ripping one of those little bastards.

    Hmm...I see a potential problem...what if some of the glue packets break open, and the condom becomes "permanently affixed"? Could be painful, ebarrasing, or both...

    "What's the next case, nurse?"

    "Another couple needs to be separated, doctor, but I'm not sure you should take this one..."

    "Why not? I'm feeling fine."

    "Yes, doctor...but...she's your daughter."

  • The composite can only fix the crack once, and the forces that caused the crack are still there, so the composite WILL break again. The only solution is a better design that won't put so much stress on that composite or replacing the composite with a new one. Further, the glue is only a quick fix, a hack, that should only last until an engineer is available to fix the material with a new one. Someone mentioned earlier that the glue should be colored so that it indicates cracks (though it would be very disconcerting to go over an older bridge and see bright green spots on all the girders). While the technology is cool, it's a wrong step in terms of safety and in terms of proper design in engineering applications.
  • Aplying this material to our socks just may solve the age old mystery of -- "did the washing machine eat the left sock?" :-) Anyways, I could think of a lot more usefuly applications than just socks. Think of the more practical uses like safty harnesses or suspension wires for bridges, support beams. But with all the good that this could do, there is also the bad. Once its introduced into warfare, once again the options are endless. Regenerating armor, bullet proof vests, heavy artillery that normally would require some sort of maintance after so many shots would be able to fire more and more vollies. I guess it would just be a toss up really. Wiegh the pros and cons and then decide if its worth persuing.
  • I remember watching a show where an airplaine's skin was fitted with glue capsules, so it actually "bruised", making a clear indication to mechanics where the plane's been hit.
  • we could be driving cars that are filled with some chemicals that scab and repair the body underneath just like our skin does. That would be really good

    Or we could drive cars that are filled with some chemicals that dissolve our bodies, so when we crash, we're removed from the gene pool and won't breed clumsy offspring. That would be really good.
  • A self-healing Vette would be just great for someone who live where it was a rather constant temperature all year.

    But what if you live in say, the Midwest, or in south central Texas (or anywhere else that applies) where temperatures can reach extremes? Will my Vette stop healing itself in February when it's -10 degrees F outside? Or will it never 'set' properly if it's 130 in the shade? How about on an airliner that takes off from Phoenix in August and climbs to 40k feet where the temperature is possibly well (read VERY MUCH) below freezing? Will this extreme change in temperature affect these materials?

    These are just temperatures, what about vibration during the drying of the resin. What about humidity or rain? Then consider the combinations of these.

    This is an amazing technology, and I realize these questions will be answered with more research and further testing, but the article never really metioned these possible limitations.


    I suffer from apathy, but I just don't care.
  • By having things break, however, jobs are created, and improvements are made - it is far better overall to have a rolling replacement cycle than to persist with the same crappy machinery forever.

    This must be the reason microsoft can't be broken up.

    Microsoft Lawyer: Your honor, we can't be broken up. Other companies which produce code which works the first time will ruin the economy.

    Judge: What do you mean?

    Microsoft Lawyer: Your honor, Microsoft keeps the economy healthy by causing everybody to replace their software every two years.

  • Adding glue will not necessarily make them more fragile, it will in fact make probably make them tougher in the material science and engineering sense of damage resistance. It will make them weaker (lower specific strength) and probably more flexible (lower specific stiffness).
  • In UK recently, there has been a series of train accidents due to cracks in the rails, and no later than today, problems in the tube in London. Well, I'd say there is a market here, I'm sure private companies will be delighted! :))
  • The compound retained 75 percent of its original strength after the cracks had healed for 48 hours, the researchers reported.


    So how much difference is there compared to cracks in conventional materials? Does anybody have a number on that so that I can appreciate the usefulness of this?
  • by Anonymous Coward
    now i can make a self healing dartboard of my boss's face.. =) -frigg at starofchaos.com cat message | sed -e "s/)/P first post/g"
  • That would have been nice when my SO dropped her phone last week...

    Or the time I had a close encounter with the road on my motorcycle...

    Not to mention the broken removable HD-casings..

    Paul
  • by coreman (8656) on Thursday February 15, 2001 @02:11AM (#430588) Homepage
    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.
  • Hmm.

    A self-healing material sounds marvellous, but the fact is, as in real life, things need to break, as part of the natural cycle - if not, there is a potentially greater risk to us.

    The potential that this gives is that machinery will be kept for many years - and since it won't break, it will be kept far past the point where it is safe to use.

    There will be a lot of obsolete technology in use as a result in future, which will, at best, mean the users of the technology will be disadvantaged, and, at worst, subjected to inferior safety standards compared to modern machinery.

    The fact is that much of the improvements made in society come through built-in obsolescence; without things breaking, we would be stuck using the technology of the 1940s - and no-one would want that.

    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.

    By having things break, however, jobs are created, and improvements are made - it is far better overall to have a rolling replacement cycle than to persist with the same crappy machinery forever.
  • by nerdygeek (242847) on Thursday February 15, 2001 @02:05AM (#430590)
    What happens when you come to demolish the structure? Is this going to be like throwing away a boomerang?
  • In many cases this won't help prolong the product cycles, but can help reduce the repair need. I don't think the car manufacturers would care anything about putting a few car mechanics out of business if it would give them the opportunity to claim their car cost X% less to own a year due to a lower average maintenance cost.
  • That raises the question of recycling. I would fully agree with you if a recycling policy is "bundled" with your obsolescence-based products. But this is not always the case and this approach can sometimes be harmful, like with nuclear waste.
  • This would be a great technology for condoms.
  • by ndnet (3243) on Thursday February 15, 2001 @02:22AM (#430594)
    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.
  • If there is no more demand of question for manufactured items, then those parts of industry is of no use. And if people already had what they need, they'll start using money on something else, whether on working less, or on buying other products or services, either of which will cover for the shortfall in manufacturing.

    We're not consuming goods to make anyone rich, we're consuming goods because we have needs and wants (some created by advertizing, mind you). Longer lasting objects would be bad for some manufacturers, but good for people that would prefer to spend money on other things.

  • by ConceptJunkie (24823) on Thursday February 15, 2001 @03:56AM (#430596) Homepage Journal
    >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.

  • Sad that you've probably never served in the military (I have). Sad that you've probably never worked in a place where you realize that there is a need for all these weapons (I have). Despite what you see on TV or your personal opinions, there is a need.

    Why do you feel that just because this was mentioned as something the military is interested in, that all technology is due to military needs? You like sending email? Thank DARPA. Whats to stop private corporations from using their own R&E Depts. do develop something like this? Nothing. You should be thanking the military for advancing technology.

    --Dave
  • Glad to see that you finally got a chance to make a comment that ties in with your sig.
  • The application of these fibers would be obvious. Tanks and other kinds or mobile warfare devices. Personally, I vote for Mechs. Now all we need is a Cold Fusion plant to keep the things running.

    I don't think that microscopic glue capsules are going to help with a hole the size of a manhole cover.

    Remember that for a great many modern weapons, it's one hit = one kill. The problem is usually finding the target.

    Or was I the only one who watched the History Channel Stealth show last night?
  • by Rogerborg (306625) on Thursday February 15, 2001 @04:01AM (#430600) Homepage

    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.

  • by espee (64799)
    Or colour, so you can see at-a-glance how much repairs has been done.
    A color coding scheme can tell you if the product is still safe to use.
  • Right. That's what I proposed in this [slashdot.org] thread.
  • Excuse me if this sounds somewhat foolish, but wouldn't 'real-time' be somewhat useless? A force that is breaking something may be continuous.

    Excuse me if this sounds somewhat foolish, but wouldn't 'seatbelts' be somewhat useless? A car could hit you at 90 mph head-on.

    (Even so, I'd still like the seatbelt just in case the car only hits me at 30 or 40.)


    -The Reverend (I am not a Nazi nor a Troll)
  • by RapaNui (242132) on Thursday February 15, 2001 @06:04AM (#430604)
    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 [scaled.com]

  • Perhaps it's because I deal with both electronic stuff and heavy oily stuff, I can get my head around most automotive electronics. Most of the stuff under the bonnet of a car isn't that advanced (unless you're getting into hybrids and other wierd stuff).

    Sure, it *looks* complicated, but once you see past the maze of wires and hoses, it's not that bad.

  • The US government currently uses military R&D to fund a wide variety of necessary developing technology fields. One of these is composites. If this field wasn't getting military money it would either be underfunded. In short military R&D spending is not confined to military applications. The technology used to build much of the next generation of tanks for the US military will also build much of the next generation of buses for US public transportation.
  • by Anonymous Coward

    I can see this being used in things like unmanned spacecraft and the like, but aircraft?

    Inspect and replace the parts I don't need my life depending on some glue laden part that may or may not be at full strength. Also this just delays failure as after the first crack the glue spills and sets. But the second time the glue cracks and well.....
  • by crgrace (220738) on Thursday February 15, 2001 @08:41AM (#430608)
    It's called silicon. If you heat it up (a process called annealing) the lattice reorganizes into a lower energy state. This has been known for many years and is one reason why we all use silicon chips and not gallium-arsenide. (there are many other reasons as well of course).

    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!

  • by shutdown -h now (206495) on Thursday February 15, 2001 @08:50AM (#430609)
    Airplanes already use a paint that alters it's color from impacts with things like seagulls and airborne debris. Stress lines appear in the paint from the impact of objects and the airplane safety inspectors can eyeball a plane to see if it needs a closer inspection.

    Regards...
  • 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.
    Let me introduce you to the very very American concept of "planned obsolescence".

    But then again, I suppose that's not designed so much to create jobs as to create profits.

    Tom Swiss | the infamous tms | http://www.infamous.net/

  • yeah, i know! happy, happy, joy, joy.
  • ... the main color of your car is Bondo.

    - Jeff Foxworthy
  • by snellac (314920) on Thursday February 15, 2001 @02:22AM (#430613)
    Here's Scott R. White's bio [uiuc.edu] as reported in the WP article [washingtonpost.com]. Looks like he and his students have been working on this for quite awhile:

    • A.J. Hegeman, "Self-repairing polymers: repair mechanisms and micromechanical modeling," M.S. Thesis, Dept. of Mechanical Engineering, Univ. of Illinois at Urbana-Champaign, Urbana, IL, June, 1997.
    • D. Jung, "Performance and properties of embedded microspheres for self-repairing applications," M.S. Thesis, Dept. of Mechanical Engineering, Univ. of Illinois at Urbana-Champaign, Urbana, IL, July, 1997.
  • Yeah, but I really liked my Far Side mug, and it got chipped to hell when my fiance dropped it. While I agree with you that for manufacturing and heavy industry this adds many problems - small things and trinkets improve. Plus, what about break pads that don't wear out as fast, mufflers which don't fall off as easily, and windshields that resist cracking?

    ...oh, and if they figure out how to do this with a ceramic, or a ceramic-like polymer, I'd realy like a new "I'll tell you what this means Norm - no size restrictions and screw the limit." mug.
  • I think Train Tracks would be a poor application, at least for the long term. Composites are great for offering a "fall back" where stress is expected to give movement; Composites can act as the "memory material" mentioned in the Washington Post detail. But those "glue packs" are in exhaustable supply, and eventually the material would lose resilience or its predefined shape.

    Il'l never forget when a friend was shopping for a Saturn: The Salesguy wanted to demonstrate the composite panels around the Saturn sides. He went to the "tried and true" floor model, and kicked in the door [again], but this time, it didn't pop back out. Was his face red!

    An odd sidenote about having composite doors is that you can't stick magnets (ie door signs) against the doors or quarter panels, but you can stick them on the hood or trunk, which are still metal. (At least on the SL-2.)

  • lots of products are planned obsolence. The golf club industry would hate it. At least they are looking towards hard to repair items (space stations, etc). This is just the first step. Cant wait to see the next generation...
  • I think Train Tracks would be a poor application, at least for the long term.

    The application of these fibers would be obvious. Tanks and other kinds or mobile warfare devices. Personally, I vote for Mechs. Now all we need is a Cold Fusion plant to keep the things running.
  • by Big Nothing (229456) <big.nothing@bigger.com> on Thursday February 15, 2001 @02:41AM (#430618)
    In Nature Magazine [nature.com].
  • Also, this is limited use.

    If this allows you to put just that extra shot into that tank trying to blow your tank up, then you'd be very happy with it, especially if the "healing" process can be sped up a little.
  • we would be stuck using the technology of the 1940s - and no-one would want that.

    If you drive a car you're using technology from the last century or the century before without complaining.
    IC engines date from around 1880.
    Fuel Injection? Around 1920, Bugatti IIRC
    Anti-lock Braking system? First in the late 1930's, used on WWII bombers. Composite body panels? Reliant, late 40's.

  • Stealing from canoeists? You fiend!

    for the humor impaired, please re-read the first sentence of the parent post.

  • So what if a development comes from military R&D?

    Just because microwave ovens came from military radar...does that make the food you cooked in there...tainted some how?

    Nope, it doesn't. But there is a taint in some people's minds because they have forgotten that the freedom that people in North America, Russian, Western and Eastern Europe enjoy was defended through the force of arms and military technology.
  • That is also right now - give them some time and that number my go up closer to 100% or more
  • There are lots of things we use day-to-day that aren't very strong once they start to crack, but they're overbuilt enough that regular use is below the threshold required to start cracks.

    But while I know some materials have a level of stress below which they can deform and reform without permanent damage (in metal bicycle tubing, and probably more generally, one measurement of this is the "modulus of elasticity"), I don't know if composite materials have the same deal, or if they crack under even the smallest stresses (but small cracks for small stresses).

    So, if e.g. carbon fiber composite stuff can be overbuilt to avoid cracking at all under normal use, I think that would be the best way to go. In some places overbuilding probably isn't the best way to go (e.g. Satellites), but if there is a choice, I would think overbuilt, non-glue-bubbly chairbacks would probably be preferable.
  • I'm concerned about something that's already an issue with composite construction materials - outgassing of unreacted chemicals in the adhesive used in bonding. The most typical unreacted component is formaldehyde used in the manufacture of phenol-formaldehyde resins widely used in composites. While in conventional products these fumes sill dissipate over time, if encapsulated there could be an ever-renewed source of noxious and potentially dangerous fumes
  • I think you blithly go through life analyzing peoples sig's to see if you can discover something about their stance on certain social issues. I think you are also an idiot, although that's just my opinion. I also belive you have no idea who Masamune Shirow is, nor do you appear to care. Again, you are an idiot.
  • You should play more Civilization. Copper leads to Phalanx leads to Colossus. Wheel leads to Chariots leads to cars. Face it, much of the luxuries we enjoy these days were primarily invented for military use, then adapted for use in civilian circumstances. In all honesty, do you really believe that computers would have been what they are today, if it weren't for the continuing military need to upgrade everything all the time?
  • Drawback - you'd have little green/blue/whatever crack lines one the hood of your (otherwise) nice looking car from where trucks would flip up ricks and debris on your car.


    I suffer from apathy, but I just don't care.
  • Broken and healed bones ARE weaker. The origional patterns are interupted, which makes a stress riser at the repair site. Same goes for ligaments, tendons etc. When they heal at all, they are weaker.

    This is why football players usually can't compete after age 30. All the injury sites are too weak to handle the stess of play.

    The Phantom
  • I'm really answering a lot of posts here, but bbqdeath wrote:
    >But while I know some materials have a level of stress below which they can deform and reform without permanent damage (in
    >metal bicycle tubing, and probably more generally, one measurement of this is the "modulus of elasticity")

    What you are thinking of is the "yeild stress", but elasticity is important too - that's how much a material will flex.

    The advantage with this technology is that once microscopic cracks form, the capsules burst and the material will be reglued in that microscopic area. The next crack will probably be somewhere else - once again on a microscopic scale. You won't see large amounts of glue leak out of a cracked mobile phone casing, it's likely that you won't see the crack at all. How is that useful? Every crack starts off as a small crack. A crack glued with a weak glue, or even a crack with a blunted tip, is significantly better than an open crack in any sort of stressed situation. The stress at a crack tip is a lot higher than the stress anywhere else, and as the crack cuts down the amount of material left that can take a load, the stress gets higher again. Eventually you reach a point where it is easier for the crack to grow than stay put, and it grows at a speed close to that of the speed of sound in the material, until it breaks through to the other side (eg. a 50km+ long welded oil pipe in Alaska in the '60s, with a crack moving at about 6km/s).

    In many situations strength is not the issue but toughness. Toughness is resistance to damage - copper is tough and glass isn't, hit both with a hammer and the glass will crack, even though it is the stronger material. With the material mentioned in the article the aim is to increase the toughness by sealing the cracks. If you expect single big impacts capable of producing large cracks then you would use something else, but if you are dealing with occasional loads and bumps that will cause minor damage, then this would be a useful material. This would increase the life of a part that is likely to fail by "fatigue". In many situations, reducing the strength slightly may have no effect, and in those situations where it will you may just have to pack in a bit more carbon fibre to offset the weaker glue capsules.

    Ultimately, things break in different ways, so a strong material or a thicker piece of material isn't always the way to go. If you have a thin walled steam boiler, it may crack and leak steam, if you replace it with a thick walled steam boiler, it will crack and explode like a bomb under the same conditions. If you can find or stop the cracks in time then you can deal with it.

    One example of a ceramic which is toughened by closing the micro-cracks after they form is "Partially Stablised Zirconia" or PSZ (sorry, no URL, use google). It doesn't use glue, it uses a sudden crystal structure change.

  • Using high-tech materials and a low-tech concept inspired by the human body... hmmmm, i've always thought of the human machine as one of the most awesome technological constructions to have ever existed. hell, a machine that can make its own machines!
  • Sad that you've probably never served in the military (I have). Sad that you've probably never worked in a place where you realize that there is a need for all these weapons (I have). Despite what you see on TV or your personal opinions, there is a need.

    Why is it whenever someone articulates an anti-military/pro-peace sentiment, and someone else responds to it with a pro-military/war-as-necessary-evil sentiment, can the second person never "get it" that the first person isn't just wishing for the elimination of the military forces of one side, but of all sides?

    Granted that that's never going to happen, but still... the pro-military people always think that an anti-military person wants the elimination of their own armies, leaving their country vulnerable to invasion from outside armies. They don't want that. No one wants that. They want all armies to go away, and no one to ever invade anywhere. I mean, yeah, that's unrealistic. But the pro-military camp always attacks the pacifist's patriotism and committment to their country, and only seldom their sense of realism.

    I rang, you rang, we all rang for orangutang!

  • Self-healing structures have been around for years. Tetrapod structures are an example. Tetrapods are the large, strangely shaped concrete blocks used in breakwaters and coastal protection schemes. Basically, the more the ocean pounds the blocks the tighter they lock together. Here is a page of Pictures by SYS (Malaysia) [sys.com.my]. The original company to create them I believe is French, but URL is hard to get. The US Mil has some graphics here [army.mil].

    Anyway, self-healing is one thing, these blocks go one further, and the more they take punnishment, the stronger they get.

Those who do not understand Unix are condemned to reinvent it, poorly. - Henry Spencer, University of Toronto Unix hack

Working...