The researchers faced several challenges along the way. The first was related to modeling and simulation for the process, which is a combination of sheet metal forming and injection molding. Existing software for sheet metal forming processes can’t model the flow of the polymer, while packages for injection molding processes can’t account for deformation of components. “We had to develop custom models for our process and, based on those models, create our own simulation tools to better understand the process,” says Farahani.
The team has also addressed tactical challenges for potential industrial applications, such as the opposing phenomena of “spring back” in metals during the deformation process and shrinkage of materials during injection molding. Farahani and Pilla developed a patent-pending method to prevent the ensuing delamination and debonding. They also have integrated sensors in the tooling and utilized advanced modeling and artificial intelligence to better control the process and monitor the final quality of the hybrid component.
“We now believe this process is mature enough to be implemented in industrial applications,” says Farahani. He adds that hybrid single-shot manufacturing can not only reduce the aforementioned difficulties and limitations in manufacturing multi-material structures, but also opens up new opportunities to cost-effectively produce multi-functional, smart components. The added functionality can be diverse, and the emerging applications can go beyond automotive, including aerospace, consumer markets, biomedical and construction.
“We foresee applications in any domain where there is a necessity for complex geometries with diverse functionalities,” says Pilla.
CNT Curing for Aerospace Parts
Project: Carbon nanotube porous networks
School: Massachusetts Institute of Technology
Principal Investigator: Brian L. Wardle
More than a decade ago, researchers at MIT and Metis Design were testing sensors made with carbon nanotube
(CNT) networks under funding from the Air Force Office of Scientific Research when they noticed something interesting. Depending on how they were measured, the CNT heated up.
This tangential discovery led the researchers to investigate CNT films as lightweight resistive heaters, which the Naval Air Systems Command (NAVAIR) funded to develop into an embedded deicing system for aircraft.
During that project, Brian L. Wardle, professor of aeronautics and astronautics at MIT, says the team realized the technology might work for curing: “We’re placing a heater on this aerostructure for ice protection. Why don’t we use that heat to actually cure the part underneath in the first place? It sure gets plenty hot.” Fast forward to today and that is exactly what MIT and Metis Design are doing on behalf of NAVAIR – developing a CNT-based conductive heating technique that, when combined with carbon nanoporous network (NPN) film, can be used to manufacture aerospace-grade composite materials.