A new 3D printed lattice structure has surprised researchers with its strength and lightness. It uses two different lattice structures merged together, eliminating the weak points typically found in these complex shapes. Researchers at RMIT University in Melbourne, Australia, took inspiration from hollow-stem water lilies and organ-pipe corals to study how to reduce the high stress concentrations created by joints.
"Ideally, stress should be evenly distributed in all complex honeycomb materials," said Distinguished Professor Ma Qian, first author of the new study. "However, for most topologies, typically less than half of the material is primarily subjected to compressive loads, and the larger volume of material is not structurally important."
The researchers strengthened the tubular lattice by covering it with a second lattice on top, and added a thin X-shaped cross-section between the tubes and connections to distribute the load more evenly during compression testing.
Its shape is very complex, but easy to manufacture using a laser powder bed fusion 3D printer. The researchers tested the resulting cube and found that it was 50 percent stronger than WE54, a cast magnesium alloy of similar density used in the aerospace industry.
Depending on the printer, which can range in size from millimeters to several meters, they say it can withstand temperatures up to 350°C, or up to 600°C if upgraded to a more heat-resistant titanium alloy.
The researchers say the material could be useful in areas where strength and weight are important, with possible commercial applications including aircraft and rocket components. Interestingly, they also say that the material could also be used in medical bone implants, and that when it fuses with the body, the complex, partially hollow shape could eventually be filled in by regrowing bone cells.
But are such complex structures easy to fabricate? The researchers admit: "Not everyone has a laser powder bed fusion machine in their warehouse. However, as the technology develops, it will become more accessible and the printing process will become faster, allowing more people to adopt our high-strength multi-topology metamaterials in their components. Importantly, metal 3D printing technology can easily create mesh shapes for practical applications."
The RMIT team is calling on companies that want to collaborate and commercialize these metamaterials across a range of applications, saying it will continue to refine the lattice design in the quest for greater strength and lighter weight.
The paper was published in the journal Advanced Materials.