Self-Healing Composites- The Trick is Biology
Let’s face it, things wear out. Car tires go bye-bye, seals get worn, and Jets need constant upkeep to make sure that cracks in the fuselage [the main body of an aircraft] don’t become points of failure. Thanks to a new technique right out of the labs at the University of Illinois, things may still wear out, but they will also self heal.
If you have ever seen anything made of fiberglass, or better yet have worked with fiberglass [itchy!] you can see the finished product isn’t one solid piece, it is layer upon layer. This poses a unique problem that metals and other materials don’t have to face when it comes to wear.
Delamination [separation of the different layers] poses a big problem, in fact it can cause critical failure of a part if not kept in check. So how do you combat a problem like that? You take a cue from biology, at least that’s what professors Nancy Sottos, Scott White, and Jeff Moore thought to do.
The innovation comes in the form of a vascular system [a fancy term for a set of tubes, like the veins that pump your blood]. What the researchers did was layer the fiberglass and resin [the glue] but inserted a ‘sacrificial’ line, similar to fishing line, throughout the piece. When they finished the part, they heated it until the line evaporated and what was left was just the micro-tube system in the fiberglass.
Next they filled some of the tubes with a type of epoxy resin and the others with hardener. This meant that when the tube is punctured or cracked, the resin and hardener would mix and repair the damage, like a scab over a cut.
[Loony hint: Epoxy is a type of strong glue that is typically the consistency of a sticky and thick syrup, left exposed to air it doesn’t do much, but when combined with the hardener the glue dries and creates an incredibly strong bond between the materials]
This turns out to be a very effective approach that gave almost 100% repair to the wear of the part, even when being damaged several times over.
“The beauty of this self-healing approach is, we don’t have to probe the structure and say, this is where the damage occurred and then repair it ourselves,” said Jason Patrick, a Ph.D. candidate in civil engineering and lead author.
Notably like the vascular system in your body, it isn’t straight lines. As seen in the image above the microvessels were woven in and overlapped. This allowed further mixing of the two components released, which was important because mixing the hardener with the resin thoroughly is needed to insure a complete dry of the epoxy.
So when will we see this commercially? Chances are good that it will be soon. The techniques used can be applied to the manufacturing processes used today not to mention the cost to add this type of technology is relatively cheap.
All this means that you should keep an eye out for self healing materials in a store near you!
Want the dry technical version? You probably want the full article which you can find — here!
Patrick J.F., Hart K.R., Krull B.P., Diesendruck C.E., Moore J.S., White S.R. & Sottos N.R. (2014). Continuous Self-Healing Life Cycle in Vascularized Structural Composites, Advanced Materials, n/a-n/a. DOI: 10.1002/adma.201400248