New metamaterial could be stiffest thing in the known universe

23 Feb 2017

The Isomax structure. Image: UCSB Engineering

A team of researchers has revealed a new 3D metamaterial that could make incredibly efficient and strong aircraft designs.

Many scientists try to push the limits of what is physically possible, and the latest effort comes from a group of UC Santa Barbara researchers, who believe they have created a design to reach the theoretical limit of stiffness.

After two years of design and research, the researchers have presented a 3D pyramid-and-cross cell dubbed Isomax.

The combination of solid foam and air pockets – working with some advanced geometry – has resulted in a material that is not only mostly air, but incredibly strong.

Unlike a typical design of bubbles or a honeycomb arrangement, the ordered cells were set apart by walls forming the shapes of pyramids with three sides and a base – an octahedral – reinforced inside with a cross of intersecting diagonal walls.

Therefore, Isomax’s cell structure makes it possible for the material to resist crushing and shearing forces without the need to make it heavier or denser.

Despite computer models showing that the design would indeed push the theoretical limits of stiffness, its original designer, Jonathan Berger, was open to scrutiny from his peers.

Useful for aerospace design

“There was obviously a lot of positive feedback, but for me as a scientist, it’s a bit too much hand-waving until you have something in a peer-reviewed journal”, he said, with his findings being published in the journal Nature.

“I carried out some simplified calculations of the stiffnesses of some of the foams and was able to see that the pencil-and-paper results agreed with the computer calculations,” explained Berger’s research partner Robert McMeeking.

“This gave us confidence that the computer calculations were both correct and being formulated accurately.”

The potential uses of the metamaterial in the commercial world are nearly limitless, but researcher Haydn N G Wadley believes that it would be particularly useful in transportation.

“It will also be an excellent thermal insulating and sound-absorbing material. Potential applications for this ultralight material are likely to emerge in aerospace structures, for lightweight automobiles and in many robotic machines, especially mobile types that carry their own power and must manoeuvre.”

Colm Gorey was a senior journalist with Silicon Republic