Light Makes Right: Inside RMI’s Autocomposites Workshop
“Might makes right.” The popular aphorism has been around for centuries, and the perspective it offers for millennia. It’s been applied to everything from one nation conquering another to the National Football League. It’s also been applied to automotive engineering—the idea that bigger and heavier is associated with all sorts of desirable qualities, such as safety, strength, and durability.
Witness Volkswagen’s commercial “Door Thunk” for the 2012 Jetta. The narrator intones, “The solid thunk of the door on the Jetta: another example of Volkswagen quality. That’s the power of German engineering.”
But now, ultralight, ultrastrong materials—alternatives to traditional steel—offer the promise of an entirely different scenario. What if we replaced that heavy car door—and its “thunk”—with a superlightweight, superstrong door … one that effortlessly swings closed and shuts with nothing but a light click? What if light makes right?
RMI explored answers to those questions at our Autocomposites Workshop, held November 7–9 in Troy, MI, and attended by U.S. automakers, their suppliers, raw material producers, government representatives, and academia. One of RMI’s chief long-term goals is to wean the U.S. off of its dependence on oil. Not surprisingly, engaging the automotive sector is an important piece of that puzzle.
Shifting the automotive sector away from oil dependence will involve a multipronged strategy, including dramatically increasing vehicle fuel efficiency and vehicle electrification. Both of those will be enabled, in part, through the adoption of ultralight, ultrastrong auto bodies made of advanced materials, since weight is tied to both fuel economy and the powertrain.
Carbon fiber offers some of the best promise for making such a transition to lightweight-yet-strong vehicles, thanks to its superior strength- and stiffness-to-weight ratios. But while carbon fiber has already been adopted for bicycle frames and some niche sports car applications, broader adoption in the automotive industry has been slow to come. Besides, swapping traditional steel for an all-carbon-fiber auto body is a tall order.
The focus of RMI’s Autocomposites Workshop, then, was to identify specific subassemblies that would make excellent candidates for initial adoption, in order to gain some early industry traction. We worked together to identify a piece of a car—such as a door—that is already made from multiple smaller pieces (and held together with rivets, bolts, welds, etc.), and replace the entire subassembly with a single piece of molded carbon fiber that is both lighter and stronger than the original. By doing so, we would unlock elements of value that offset carbon fiber composite’s higher material cost, for example, demonstrating it as a viable option in the here and now, as well as in the future.
A car door—with an average weight around 50 pounds—turned out to be an excellent candidate. On the one hand are qualitative benefits that are very real yet harder to measure. A lighter door could be more easily opened when your hands are full. It would be less likely to slam shut unintentionally, such as when parked on a hill. The window frame could be thinner and the window larger, thus improving visibility (which affects the driving experience and safety).
On the other hand are quantitative benefits. A lighter door also means lighter hinges, attachments, and framing, further reducing an auto’s weight. If you swapped out all four doors of a sedan for carbon fiber composite versions, that cumulative weight savings alone could result in fuel savings of nearly $100 per year (net present value). Meanwhile, you’d incur an upfront material cost premium of about $800, yielding an eight-year return on investment. Vehicle fleets aside, most individual consumers aren’t willing to pay for much more than a three-year cumulative fuel savings in the purchase price of a vehicle, so the aforementioned safety and functionality benefits will play a critical role in the business case for carbon fiber composites.
Nevertheless, that business case is strong—a carbon fiber composite door stacks up very well against its business-as-usual steel counterpart, even at today’s material prices. There’s much yet to be done, however. Shifting to a new manufacturing paradigm that includes carbon fiber composites entails an investment in new tooling and equipment, and will require better design and analysis simulations to get maximum benefit and minimum waste from the material, as well as technological improvements to make carbon fiber repairable and recyclable.
At the end of the three-day workshop, participants identified key roles for business, government, and academia to play both in strengthening the initial business case for lightweight, composite-intensive vehicles and in paving the way for their widespread adoption in the longer term. One such proposed approach is a Detroit-based collaborative research and manufacturing center, with the express purpose of tailoring the material technology and manufacturing methods to automotive needs, in order to put the U.S. squarely on the forefront of a transformed global automotive marketplace built around lightweight vehicles.
One day—hopefully in the not-too-distant future—we’ll succeed in fostering a world where, when it comes to our cars, light does make right.
A full report of the Autocomposites Workshop proceedings, findings, and next steps will be available January 2013 at https://rmi.org/Autocomposites.
Some images courtesy of Shutterstock.