In 2015 UC Santa Barbara mechanical engineer and materials researcher Jonathan Berger introduced an idea that could alter the way people think about high-performance structural substances. Two years later, his concept is paying research dividends.
Known as Isomax, the beauty of this solid foam, in this case loosely defined as a combination of a stiff substance and air pockets, lay in the geometry within. Rather of the typical assemblage of bubbles or a honeycomb arrangement, the ordered cells were set apart by walls preparing the shapes of pyramids with three sides and a base, and octahedral, reinforced inside with a ‘cross’ of intersecting diagonal walls.
The link of the pyramid and cross-shaped cells, said Berger, resulted in a structure that had low density, mostly air in fact, yet was uncommonly robust for its mass. “The Isomax geometr is maximally stiff in all directions,” explains Berger. Other geometries – a honeycomb, for instance, may be able to resist forces from single direction, but approach it from a distinct direction and the cell will collapse conveniently. Isomax’s cell structure makes it feasible for the substance to resist crushing and shearing forces without the requirement to make it denser or heavier.
But, for all the early interest that his proposed metamaterial generated and the computer modelling that supported his claims, Berger knew he could not rest till science backed him up. “There was obviously a lot of positive feedback, but for me as a researcher, it’s a bit too much hand waving till you have something in a peer-reviewed study,” says Berger.
“I carried out some simplified estimations of the stiffnesses of some of the foams and was able to witness that the pencil and paper results agreed with the computer calculations,” explains McMeeking, whose study emphasis on computational science and engineering as well as the mechanics of substances, comprising their durability and fracture. “This gave us the confidence that the computer estimations were both accurate and being formulated precisely.”
The equations and closed-form solutions introduced to create the mechanical model of the behaviour of metamaterial matched up beautifully,” with the earlier computer models, confirms Berger.
“Given its properties, Isomax is going to be a highly interesting metamaterial,” says Wadley, whose study spans the synthesis, performance and structure of new substances. “It will also be an amazing thermal insulating and sound absorbing substance. Potential applications for this ultralight substance are likely to emerge in aerospace structures, for light weighting vehicles and in numerous robotic machines, especially mobile sorts that carry their own pore and maneuver.”
The development could not have better timing. As resources become more constrained and concern for energy efficacy grows, a substance with such mass relative to its strength would need fewer resources to produce and less fuel to transport. The simple geometry makes it versatile enough to structure for a range of situations, and functionally graded, it can be employed to prepare objects with varying levels of stiffness from one end to another.
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