Visiting engineering professor works on materials designed for additive manufacturing

Many professors publish research papers but never get to see their research move into the development phase.

That's not the case for Daniel Tortorelli, an engineering professor at the University of Illinois Urbana-Champaign.

He recently completed a nine-week sabbatical at Lawrence Livermore National Laboratory, where his research on structural optimization was put to use in the Engineering Directorate's additive manufacturing lab.

Tortorelli is working with LLNL engineer Chris Spadaccini and his team to use computational modeling methods known as topology optimization to create designs for micro-architected materials, which can be fabricated with additive manufacturing.

"It's nice to know that my research is being used here," Tortorelli said. "Professionally, it has been a great experience at the Lab, seeing science and technology applied to all these problems."

Spadaccini is leading a multidisciplinary team at the Lab, which collaborates with academia to combine sophisticated computer modeling with new additive manufacturing techniques to design and fabricate micro-architected materials with desired combinations of properties. The Laboratory Directed Research and Development Program (LDRD) and Department of Defense's Defense Advanced Research Projects Agency (DARPA) fund these projects.

Tortorelli is using his topology optimization research to create designs for micro-architected materials in three areas: thermomechanical microstructures, electromagnetics and lithium-ion batteries.

In thermomechanical microstructures, the LLNL team is developing zero and even negative thermal expansion composite materials for applications such as athermal optical mounting hardware to support various optical components in thermally varying environments such as space or on flying drones.

Tortorelli is optimizing the "unit cell" morphologies of these composite materials. Zero and negative thermal expansion materials are obtained by combining two constituent materials with disparate stiffness and thermal expansion. 

These materials are being fabricated using micro-stereolithography, a process co-developed by LLNL and the Massachusetts Institute of Technology (MIT). Their manufacture and subsequent testing are being performed at LLNL.

In electromagnetics, Tortorelli is working with the LLNL team to develop photonic devices. He is designing the micro-architectures of photonic crystals for various applications (e.g. metamaterials with negative refractive indices, band gap structures, lenses and cloaking devices).  Band gap designs for the microwave regime will be fabricated and tested at LLNL.

Finally, Tortorelli is working with the LLNL team to develop advanced electrodes for batteries.

"We are looking at designing the geometry of the battery electrodes to get better power density," he said.

When he returns to the University of Illinois, Tortorelli said he will continue working on the architected material designs for additive manufacturing and hopes to continue to rapidly produce results in these high-impact applications.

"I anticipate coming to the Lab more in the future," he said.