In most large constructions, rigid, dense and heavy support beams are used to keep a structure from crumbling in on itself.  But for some applications, having dense structural components is a drawback. Researchers in Europe have shown that the density of structural components can be greatly reduced if they’re constructed around a fractal pattern.

A fractal is a mathematical set that has repeating self-similar patterns throughout its structure.  If you were took look at a fractal set from a microscopic view, it would appear identical to itself on a macroscopic level and at every level in between. Fractal sets are an example of hierarchical patterns, where the same basic shape is repeated throughout a structure at different scales.

Yong Mao and his colleagues at the University of Nottingham have developed a framework for creating structures where “optimal hierarchical order of the structure depends on the load it needs to withstand.” What this means is that for any structural element, a fractal pattern can be iteratively created to reduce its material needs to the bear minimum.  This reduction in material would be customized for each form to maximize the amount of material that can be subtracted.

Yong Mao’s team confirmed their theory by creating a crane boom that was 100 times lighter than a traditional solid steel boom.  The team then let their imaginations run wild regarding their theory’s possible applications. Mao’s team believes that their technique could be used to builds booms for solar sails.   

Solar sails are  discreet spacecraft propulsion systems that behave similar to wind sails, except instead of using wind to drive a craft, a solar sail uses radiation pressure. Unlike wind, radiation pressure is extremely weak, and therefore, solar sails will need to be large in order to gather enough pressure for propulsion. But since solar sails would be doing their work in outer space, their booms don’t have to battle the forces of gravity and can therefore be extremely lightweight.  

So what does this have to do with 3D printing?

Well, creating these fractal structures is nearly impossible with subtractive manufacturing techniques. According to Mao, “Even a small imperfection at a local scale could have a large impact as there is no extra material that could take the added stress and maybe that is why this kind of fabrication has not been practical to date,” Mao believes that in the future, 3D printing technology will be accurate enough to produce his team’s lightweight fractal structures. “We could just upload our designs to a program and people could download and print off the structures at home”.

Read More about Mao’s Research at Physical Review Letters

Image Courtesy of PhysicsWorld and Wikipedia

 

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