The microscopic structure of a material plays a huge role in how well it absorbs impacts, and now researchers at Los Alamos National Laboratory have hit upon a structure that works particularly well. The team 3D-printed cubes with fractal voids inside them, which could be a useful structure for new materials in helmets, armor and other protective items.

Materials that need to be shock-resistant are usually structured with gaps to help dissipate the shock waves. But the exact shape of these structures is still being experimented with, as researchers test “nanofoam”, herringbone, honeycomb, and microlattice patterns, among many others.

For the new study, researchers at Los Alamos investigated fractals. These intricate patterns consist of structures that repeat on smaller and smaller scales, and in this case that meant cubes with hollowed-out pores dotted through them.

The team 3D-printed plastic cubes with fractal voids carved into them, with varying levels of detail. Then, they tested how well each design withstood shock by firing impactors into them at about 670 mph (1,078 km/h).

The researchers found that the more intricately structured the cubes, the better they were at dissipating shock waves. Some of them were as much as five times better at the job than solid cubes made of the same material.

The team says that this structure of fractal void cubes could inform new protective materials for vehicles, helmets, body armor, and other things that might need to withstand shock waves.

That said, the researchers acknowledge that the current design isn’t necessarily the most effective. Next up, the team is investigating other void shapes and structures with the help of optimization algorithms.

“The goal of the work is to manipulate the wave interactions resulting from a shockwave,” says Dana Dattelbaum, lead author of the study. “The guiding principles for how to do so have not been well defined, certainly less so compared to mechanical deformation of additively manufactured materials. We’re defining those principles, due to advanced, mesoscale manufacturing and design.”

The research is due to be published in the journal AIP Advances.

Source: Los Alamos National Laboratory