Materials that heal themselves

25 May 2008

Interview with

Ian Bond

Chris - Scientists at Bristol University, and this is a piece of research led by Dr Ian Bond, have come up with a material that can automatically put things right. Ian's with us to talk about it. Hello Ian, thank you for joining us. How does this actually work?

Ian - We've been developing, over a couple of years now, a composite material that can self-heal. We have small vessels inside the structure with a liquid inside them. Upon a damage event these rupture and bleed out liquid to effect some kind of healing within the structure.

AeroplaneChris - What are the chemicals you are using to do it?

Ian - We've been concentrating primarily on using standard 2-part epoxy systems which are the mainstay of the aerospace industry. There's obvious improvements that can be made to those because they're pretty much off-the-shelf systems at the moment.

Chris - So the way it would work is you would have one chemical in one type of tube, one in another and where the damage is the two chemicals are blended together and they react?

Ian - That's exactly how it works so you do need both of them to be present. I guess one of the challenges at the moment is somehow making that reaction or mixture less sensitive to the particular mixed ratios, for instance, so that you can have quite a robust healing process that's not dependent on a certain amount of one or the other being there.

Chris - How much of this stuff do you need and what are the applications for this immediately here on the ground.

Ian -   We're looking to address the very subtle damage in the structure. If there's a hole in the structure, for instance we like to think that somebody may notice that beforehand. It's the dings and bangs and wear and tear. It's the small cracks that begin in the structure which are difficult to detect which we're hoping to address.

Chris - So this would be aeroplanes, cars even?

Ian -   It could be used in cars, yeah. I guess safety critical structures are what we're aiming at primarily. I guess in a car if it breaks you can generally pull over to the side of the road. In an aeroplane you don't have that option. Certainly in space you definitely don't have the option.

Chris - How much weight does this add? In the aerospace industry weight is everything. Does this make a plane weigh twice as much and therefore it's not going to be useful?

Ian -   The idea here is although we may be adding some weight you can use lighter weight structures. At the present design is such that you allow for damage from day one. You have to have a heavier-weight structure than you would otherwise. You have to cope with the fact that you're fighting with one hand behind you back, as it were. You're assuming there's damage there. If you could somehow build in an ability to recover some of that damage by healing you could potentially have a lighter-weight structure overall.

Shuttle LaunchChris - With the current missions to Mars on the agenda for the next 30 years or so and the fact that space rockets get hit by things like micrometeors quite often could this system work in space?

Ian -   It could do. We've done some previous work looking at this. There's a lot of challenges. The temperature is an issue, the low vacuum. The extremely high velocity of the impact you mentioned from things like micrometeoroid. I guess it's the inner structure you might want to protect where they're perhaps not as exposed to the external environment. You want to maintain structural integrity on say a liner where you have a manned vehicle. I wouldn't necessarily advocate that we use this on an external structure that's going to be hit by a micrometeorite but it could be used in some form, perhaps in an inner structure within that.

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