Many industries are looking for ways to reduce the weight of their products. In the automotive and aerospace sectors, it has been shown that lightweighting can most effectively be achieved through multi-material structures comprising polymeric composites and metal. Effective joining methods are needed to assemble those metal and non-metal substrates together into a structure, and U-M researchers took a multidisciplinary approach to deliver a process that outcompetes existing methods in multiple manufacturing domains.
Lightweight multi-material structures offer possibilities for enhanced function and environmental sustainability in addition to the obvious benefit of lowering the overall weight of a car or plane. Manufacturing these structures relies on metal-to-polymer joining methods that must create strong joints and be time- and cost-effective. Traditional mechanical joining methods such as fasteners and adhesives falter on at least one of those requirements.
The new approach from U-M joins metals with polymers at a molecular level, creating chemical bonds between the two materials. A specifically designed tool applies the right temperature and pressure for chemical bond formation at the joint. The chemical bonds formed are stronger than mechanical ones, checking off the strength requirement.
The method can not only create stronger polymer-metal composite structures, but it’s also more time- and cost-effective than mechanical methods. Compared with adhesives, for example, it’s 10 times faster, joining materials at rates as fast as 5m/min. Replacing adhesive joining with this novel method would also eliminate the purchase, storage, maintenance and disposal of many industrial adhesives required today to join dissimilar panels together.
Spearheading the project are U-M researchers Pingsha Dong and Fengchao Liu. Dong is Director of the Welded Structure Laboratory and a professor of Mechanical Engineering and Naval Architecture and Marine Engineering. Liu is a research scientist in the department of Naval Architecture and Marine Engineering.
The group approached what is traditionally a physics problem by also contemplating the chemistry of the materials. Welding was a good place to start since it’s a discipline that focuses on combining materials at the molecular level.
“If you look at the research ten years ago, no one had tried welding,” said Liu of the early days of the group’s effort. Liu and Dong’s team developed computational models to identify the theoretical temperature and pressure needed to form chemical bonds between different metals and polymers, then identified the actual conditions needed through experimentation.
In 2019, Dong and Liu connected with Innovation Partnerships to file patents and acquire funding and commercialization guidance for their program.
Keith Hughes, Associate Director of Licensing, Physical Sciences & Engineering was the first point of contact. “We needed someone with a commercialization and manufacturing background to know what to do next. [Keith] is very knowledgeable and up-to-date on emerging needs and ongoing issues that industry wants to resolve,” Dong said. With a novel technology and a market need, the team pursued patent protection.
The next step was to acquire funding. Mentor-in-Residence Don Manfredi identified the Michigan Translational Research and Commercialization (MTRAC) Advanced Transportation program as an appropriate potential source of funding for Dong and Liu’s research. Manfredi, who is now Associate Director of Ventures, Physical Sciences, became aware of the substrate joining project after attending meetings between the inventors and Hughes. MTRAC Advanced Transportation is a statewide program funded by the Michigan Economic Development Corporation, one of five statewide MTRAC programs that fund the commercialization of university research into products or services that shape the future of transportation technology or that address poorly met transportation market needs.
“Don was instrumental in the MTRAC funding. We weren’t familiar with that program and with his encouragement, we applied,” said Dong. The team’s application was successful and they were awarded $100K to de-risk and further commercialize this technology over the course of the one-year program.
In addition to monetary support, Dong explained, “MTRAC gave us the ability to collect data and engage with industry.”
Upon completion of the MTRAC program, Dong and his team were able to successfully develop their technology leading to a license with a tooling manufacturer to develop and bring a machine to market that can directly join polymer to metal and other combinations of dissimilar materials in a factory environment.
Dong and Liu’s research portfolio includes other joining and additive manufacturing methods. The innovators created a method to join aluminum, a material commonly used in structural lightweighting, with steel where the joint is not structurally fragile, a problem that plagues existing joining methods.
In additive manufacturing, the research team developed a tool called SoftTouch to deposit dissimilar metals that don’t need to be performed in a vacuum as in current methods and is amenable to 3D printing. The approach removes cost, time and infrastructure barriers to additive manufacturing.
Dong and Liu continue to innovate in their lab and have several new technologies being developed in addition to ones they have already commercialized. As for the continuing relationship with Innovation Partnerships, Dong said, “Keith has become habit now. If I see a commercial opportunity, I ask if Keith can join the meeting so that I can get his take. From there Keith brings in other appropriate members from the Innovation Partnership’s team based on what our needs are. It’s a great partnership.”