Researchers at Lawrence National Laboratory (LLNL) have devised a new type of 3D printed lattice compositions. The new structure mixes high stiffness and lightweight. This is despite going against a rule previously believed to be expected to show such attributes.
One of the newly designed structures further shows an excellent uniform reaction to forces in every direction.
The LLNL led co-led by engineer Seth Watts utilized topology optimization software. Watts this wrote to make two exceptional unit cell patterns comprised of micro-architected trusses. One of them was created to have isotropic material attributes. These fresh compositions were then manufactured and experimented. They were discovered to outdo the octet truss, a usual geometric design for 3D printed lattice structures.
The researchers were surprised to learn that the trusses seemed to go against the Maxwell criterion. This is a theory of structural stiffness utilized in a mechanical pattern. It asserts that the most effective load-supporting structures disfigure only through stretching.
For such structures, rigidity balances linearly with weight. Reducing the weight of the structures in half only lessens its stiffness by half. This is contrary to less effective structures whose rigidity would be lessened by ¾ or ⅞. This linear scaling allows the making of ultra-lightweight, ultra-stiff automatic metamaterials.
“We have found two trusses that have linear scaling of stiffness with density when the conventional wisdom — this Maxwell criterion rule — is not satisfied,” Explains co-lead author Watts.
“It had been believed that the Maxwell criterion was both necessary and sufficient to show that you had high stiffness at low density. We’ve shown that it is not a necessary condition. In other words, there is a larger class of trusses that have this linear scaling property.”
He also said that it showed that what as previously orthodoxy is not stable. There are exemptions and exemptions actually can give you excellent attributes.
The LLNL team created structures with a recurrent octahedral and rectified cubic (ORC) unit cell created to be firm than an octet truss of similar density. These designs were validated through experiments.
Also, the researchers stated that because of their consistent reaction, isotropic lattices may be put arbitrarily. This is with regard to obvious or even unknown loads. This enables engineers to create firmer structures as compared to those made with other types of trusses such as the octet design. This design also is ultra-firm but only in specific directions.
“The isotropic truss allows you to disregard the load direction in a use-case scenario,” commented paper co-author Chris Spadaccini, director of LLNL’s Center for Engineered Materials and Manufacturing.
“For example, you would no longer have to worry about what angle the loads are coming from. This work really shows that there’s a new method that can get you better performance but has not been explored because it violates conventional wisdom.”
According to the researchers, the work confirms that by use of topology optimization, experts may create new structures. These structures can outdo those made with conventional design-by-rule strategies.