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Fractal cube structures show promise for dissipating shockwave energy

Fractal cube structures show promise for dissipating shockwave energy

Shockwaves are dissipated five times better by 3D printed fractal structures with closely spaced gaps than by solid cubes.

“The goal of the work is to manipulate the wave interactions resulting from a shockwave,” said Dana Dattelbaum, a scientist at Los Alamos National Laboratory and lead author on a paper to appear in the journal AIP Advances

 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.

Shock-dissipating fractal cubes could forge high-tech armor
Simulations show how fractal structures of increasing complexity dissipate energy from shockwaves. Credit: Los Alamos National Laboratory

Shockwave dispersion materials that take advantage of voids had previously been created, but they mostly used random distributions determined via trial and error. Layers have also been employed by others to reverberate shock and release waves. Controlling the position of holes in a material precisely helps researchers to create, model, and test structures that work as intended, in a reproducible way.

The researchers tested their fractal structures by firing an impactor into them at approximately 670 miles per hour. The structured cubes dissipated the shocks five times better than solid cubes of the same material through two effects: viscoplastic deformation and associated energy conversion to heat, and edge-release (rarefaction) wave interactions on relevant timescales to shockwave propagation. In the first case, the analysis has shown high localization of the dissipation energy at the interfaces yielding to a high increase in temperature in these regions.

Despite its effectiveness, it is unclear if the fractal structure is the optimum shock-dissipating design. In pursuit of optimal architectures to absorb shocks, the researchers are looking at various void- or interface-based designs. New optimization algorithms will direct their attention to structures other than normal, recurring formations. Potential uses include vehicle structural supports and protective layers, helmets, and other human-wearable protection.

Shockwave dissipation by interface-dominated porous structures, D.M. Dattelbaum et al.

Published: July, 2020

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