Australian researchers have constructed the world’s first floating titanium structure made possible by 3D printing
The creation of 3D-printed floating titanium is a promising new material for marine infrastructure by overcoming the fundamental challenge of making metallic lattice structures float.
The titanium material is strong and lightweight, floating in water even after severe damage.
The research study led by RMIT University is the first reported demonstration of a floating metal-hybrid lattice metamaterial, while its sustained buoyancy was validated by samples that floated in freshwater for more than two months.
“Although metallic lattices can be incredibly light with densities less than one-tenth the density of water their open, interconnected spaces allow water to enter, causing them to sink. This has made these strong, lightweight structures unsuitable for marine infrastructure until now,” said RMIT’s Centre for Additive Manufacturing lead researcher Dr Jordan Noronha.
The titanium lattice, which is made up of hollow, interconnected struts filled with foam, floats and can withstand seawater exposure .
“By filling only the hollow titanium struts with polyurethane foam, we created a structure that allows water to flow through it while remaining buoyant even after significant cracking and damage,” added Noronha.
The floating titanium lattice is 70 per cent stronger than stainless steel or the high-density plastic currently used in jetties, buoys and floating sensors when compared at the same overall density.
To achieve this, researchers developed a new measure, called skeletal density, to predict whether open structures will float.
Conventional density calculations include all the open space within a lattice structure, even though water can occupy this space and it therefore does not contribute to buoyancy.
Skeletal density instead considers only the parts of the structure that exclude water. In this case, the titanium walls and sealed, foam-filled channels.
“This gives engineers a simple design rule: if the skeletal density is lower than that of the surrounding liquid, the structure will float – even when water flows through all its external openings,” explained Noronha.
The titanium lattice performed well in short-term corrosion testing using natural seawater from Melbourne’s Port Phillip Bay; after two weeks of immersion, the lattice only lost 0.15 per cent of its mass while its strength declined by less than one per cent.
During testing, the hybrid lattice remained buoyant even after significant damage, including cracking, failure at key connection points and the fracture of an entire lattice layer, sinking only after being severely crushed and compacted.
This is because small sealed cells in the foam trap gas and prevent water from flooding the hollow struts, so the foam acts as a distributed barrier that helps the structure remain afloat after damage.
The team demonstrated the technology with a 3D-printed prototype marine buoy that remained stable in a turbulent seawater tank rotated up to 45 degrees, without needing a sealed casing, protective coating or extra flotation.
Next steps for the floating titanium project include scaling up the demonstration parts and testing long-term performance under realistic marine and deep-sea conditions.
Develop3D readers can view the study here.
