3 replies to this topic

[primer]

Researcher Creates Strongest Metal Foam Ever

Many tests are being performed in the laboratory to determine its strength, but so far Rabiei says that the spongy material has “a much higher strength-to-density ratio than any metal foam that has ever been reported.”

Calculations also predict that in car accidents, when two pieces of her composite metal foam are inserted “behind the bumper of a car traveling at 28 mph, the impact would feel the same to passengers as an impact traveling at only 5 mph.” Applications for this amazing material are numerous and life changing.

Found this through slashdot. They do not mention the thickness of the pieces being inserted behing the hypothetical bumper, but should we presume it will fit in existing sizes of bumpers? Does it sound too good to be true? What are the downsides of a metal foam that might prevent its widespread usage in road cars? If this is for real and can be used widely it will be one of the biggest improvements in automobile crash safety!

[McGuire]

Metal foam is not new and the press blurb might mislead -- strength is not really the crux of the matter. If we wanted strength alone we would use plain old non-foam metal. It's lots stronger than any foam. The question is whether metal foam has the requisite properties for impact absorption in motor vehicles. NASCAR took a hard look a few years ago when the CoT was in the early design stages and passed. With the OEs the issues are cost and packaging. There aren't many places to put it, bumper structures being one possibility -- good for protecting the vehicle but less so at protecting the occupants. You can see how it wouldn't work in doors. As the illustration shows, in its expanded form the foam takes up five times the volume of a plain metal panel. A door using the stuff would have to be nearly a foot thick.

If you take the concept of metal foam and make it denser and more uniform in structure to idealize it for impact absorption at motor vehicle masses and speeds, then you have traditional expanded metal. And there are surprisingly few applications for it in crash structures, as it turns out. There is a red herring ("furby" in Locockian) in the press release about their material reducing the energy of a collision from 28 to 5 mph or somesuch. Cars are already designed to do that.

[imaginesix]

I once imagined that this kind of stuff might be useful in tube frames, if it could be integrated with the tubes to allow thinner walls without compromising their resistance to buckling (I dunno if there's a technical term for that).

How is the steel foam made?

[Ben Wilson]

It would probably have the same problems as any foam inside a structural member, lack of resistance to the localised heat of welding. It would probably be less horrible than 2 part foam, but it still wouldn't be good...