As one of nature’s most spectacular structures, Venus’ flower basket glass sponges can live thousands of years more than 2 km (3,300 ft) below the surface of the Pacific Ocean. Composed of lightweight, durable, flexible, glass-like silica structures, the pipe-shaped Euplectella aspergillum are also providing a stunning opportunity for aircraft and architectural biomimicry.
Building on a previous study, a team of researchers from the University of California at Berkeley and Harvard University in the US, and Istanbul Technical University in Turkey, describe their automated approach in simulations for combining and optimizing some of most useful engineering aspects of Venus’ flower baskets in new metamaterials. Their findings have been published in the journal Nature Communications.
As lead author Costas Grigoropoulos explains, his team’s approach could “optimize for both the structural and the fluidic responses of our material – something that hasn’t ever been done before in metamaterial design.” Furthermore, notes the Harvard mechanical engineering professor, the method could lead to designs for “new, lightweight, high-performance materials in many application domains, including aerostructures and biostructures.”
According to co-lead author Timon Meier, the team aimed at creating a low-mass structure that was, nonetheless, “mechanically rigid [enough to] carry a lot of force without failing.” The graduate researcher at UC Berkeley’s Department of Mechanical Engineering explained a further goal: “On the fluid dynamic side, we tried to create a structure that is not prone to any vibrations or any fluidic loads induced into the structure.”
While biomimicking a marine animal may seem like an obvious route for innovative design with underwater vehicles and buildings, the team’s approach also applies to terrestrial buildings. Whenever air or liquids flow around solid objects, they may create alternating vortices and thus oscillations that vibrate or even shake those objects, as with skyscrapers swaying in high winds. Expose such towers to high winds for enough time, and some may fail catastrophically.
“We tried to develop a design where the flow, in this case water, passes smoothly through and around the structure without causing vibrations,” says Meier.
To do so, the team employed Finite Element Analysis (FEA) for mechanics and Computational Fluid Dynamics (CFD) for flow behavior. After being programmed with the functional qualities of multiple objects, the automated process simulates and analyzes hundreds of design options, optimizing during each iteration until the reaching the best possible design currently possible.
At that point, the team stereolithographically 3D-prints the material for real-world compression testing and particle image velocimetric experiments. As the authors state in their paper, those results have been remarkable. “Optimized lattices achieve an average 140% increase in critical buckling load across a range of volume fractions relative to baseline designs, while simultaneously reducing drag, lift, and vortex shedding at porosities as low as 5%,” they state.
Grigoropoulos describes being pleased with the team’s “pretty impressive” results. “We demonstrated how you can increase the load a structure can carry just by changing its geometrical design and without increasing the volume.”
Future uses for the approach include any number of stronger, lighter structures and materials needing protection from vibration and shaking. Those range from the macro-industrial such as aircraft parts and underwater pipelines to the micro-medical such as stents that prop open bodily channels for bodily fluids.
Source: UC Berkeley
