Mechanical and aerospace engineer Dr. Afsaneh Rabiei set out to create a material “as light as aluminum and as strong as stainless steel,” and she has succeeded, in the form of composite metal foam. In this Science Nation video, she discusses its applications as a building material, a way to make car bumpers stronger, and a superior substitute to solid metal in knee and hip surgeries. A professor at North Carolina State University, Dr. Rabiei encourages her students to be “persistent and pioneering.” In her spare time, one of her passions is introducing grade school children to the wonders of engineering.
10 thoughts on “New material: composite metal foam”
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I was actually on the wikipedia article for ‘foam’ just this afternoon and down the bottom I spotted a picture of aluminium foam dating back from October 2007. I had a quick read of ‘Metal Foam’ article which is an interesting read. Four things to note from the wikipedia article, which I’m not 100% sure apply to the foam in the video; it’s flame resistant, it floats!, it could be used for body armour (i.e. impact resistant) and (of particular interest to me) vets have been experimenting with it to great animal prosthetics, hips mainly.
I’m not 100% sure what’s new about this foam? According to wiki this technique was first done in 1948!
Am I missing something? darn interesting either way, plenty of potential :)
I got slightly excited when the guy said “they showed us how the made it…” and then got completely disappointed when they didn’t show us anything other than them warming it up a bit.
There was a patent filed in 1948, so that might give us some insight. Although that system used mercury vapour, so your on your own testing that one out!
I’ll leave you with this…
“Metal foams are commonly made by injecting a gas or mixing a foaming agent (frequently TiH2) into molten metal. In order to stabilize the molten metal bubbles, high temperature foaming agent (nano- or micrometer sized solid particles) is required. The size of the pores, or cells, is usually 1 to 8 mm.”
http://en.wikipedia.org/wiki/Metal_foam
From the video, the uniqueness of this in particular is that by using hollow ball bearings you get a much more even distribution of air pockets, whereas current metal foams are uneven, and structurally unreliable.
from the article, that I didn’t see linked, doh!
“While there are other metal foams in the market, Rabiei’s is unique because she is using uniform hollow metal spheres, combined with a metal matrix. That helps the foam absorb energy much better than similar materials that have uneven cell structures or lack a metallic matrix. The foam she has created absorbs seven to eight times the energy absorbed by other metal foams made from similar materials.”
This may be a great accomplishment, and it may be great for some applications, but it is not “as strong as stainless steel” in the normal meaning of “strength”. It may have a higher strength-to-weight ratio (AKA “specific strength”). They don’t give many numbers, but when she mentions that using a metal foam bumper would make a 28 MPH crash feel like a 5 MPH one, she is wrong unless the bumper is VERY large. She also says “the solid structure of a current car is going to basically transfer all the impact energy to the body of the car and eventually to our bodies”. WRONG again, cars use crumple zones to protect passengers.
From a Makers perspective, it seems to me that if you could source the hollow metal spheres and aluminum powder, that this technique is within the realm of the more advanced Do It Yourselfer or small shop. THAT would open up all kinds of possibilities.
So who sells hollow steel spheres and aluminum powder by the pound?