TRAVERSE CITY, Mich. — Ask an automotive engineer what the ideal material for the next vehicle would be — steel, aluminum or carbon fiber composite — and the likely answer would be "all of the above."
Although material suppliers compete aggressively for program real estate, even the most ardent sales rep would admit the future lies in multimaterial vehicles.
But a serious long-standing technical problem has held back mixed materials: the difficulty of joining different materials on an assembly line.
Now researchers at Michigan State University, supported by the American Chemistry Council's automotive group, believe they have hit on a new kind of adhesive that will enable manufacturers to join multiple materials, says Sandra McClelland, a member of the council and sales development manager for Solvay Specialty Polymers. The group is promoting a new compound — a kind of super glue that adapts to different surface properties and works at different material temperatures.
Just as important, McClelland says, the group believes the adhesive will allow mixed auto materials to be cleanly separated at the end of vehicle life — another growing concern as manufacturers move deeper into recycling campaigns.
The group intends to keep patenting fees low in hopes of encouraging mixed-material vehicle design.
"The vehicles of today and tomorrow will be manufactured with a combination of energy-saving materials," McClelland said this month during the Center for Automotive Research's Management Briefing Seminars here. "Multimaterial solutions are and will provide OEMs and consumers with the best possible choices for performance, safety, aesthetics and value. All materials are in play."
The industry wants to avoid being locked into all-or-nothing uses of materials for vehicles and components. The hope is to be able to join high-strength steel to aluminum alloys, aluminum to composite or composite to steel without adding weight or using adhesives that make it hard to separate the parts at the end of vehicle life.
Consulting group Ducker Worldwide has released a study of industry vehicle weight targets showing that passenger vehicles must drop more than 200 pounds by 2025, said Abey Abraham, Ducker Worldwide North America managing director. That means that a typical car or passenger truck will add, on average, 33 pounds of polymer materials in place of existing metals.
That weight-cutting demand will only increase the need for easier ways to join a variety of materials.
"It has to be a mixed-material approach to get to these standards," Abraham said.
The adhesive that has researchers enthusiastic is an enhanced thermoplastic with extremely tiny magnetic particles that would bond different kinds of plastic, different types of metals or metals and plastic without the need for more rivets or connectors.
Because the bond can be reversed, it would allow for easier recycling at the end of the product's life.
The research is in the laboratory testing phase, McClelland said. But signs are strong for its potential in real-world situations.
The joining method also would allow a component to be repaired in a way that will make that joint stronger, she said.