Carbon Fiber's Days As the Car World's Lightweight Miracle Material May Be Numbered
The miraculous substance has never reached widespread use in mass-market automotive construction. Now, it might never happen.
The automotive world has been obsessed with carbon fiber for decades, ever since the McLaren MP4/1 Formula One race car became the first to use a carbon fiber composite chassis in 1981. Since then, the material’s signature weave, with its legendary blend of strength, stiffness, and low weight, has shown up in all forms of motorsport—as well as virtually every supercar since developed, and a smattering of mainstream road cars. To this day, its use in hoods, roofs, suspension components, strut bars, full chassis, body panels, and even decorative trim panels that serve negligible practical benefits still generates Pavlovian responses among gearheads.
Yet even in 2018, carbon fiber remains as problematic of a material as ever. It’s labor-intensive and expensive to work with, requiring careful layering and high-precision manufacturing processes. Plus, extensive demand for it in industries that arguably have more to gain from its properties—think commercial applications like airliners, or the giant wind turbines springing up like 300-foot dandelions around the world—hasn’t done anything to keep costs down.
That's not for lack of trying. Humanity is no fewer than four decades into the carbon fiber experiment, and engineers still jump up and down with every bit of incremental progress in making it more affordable and easier to manufacture. And those efforts are massive: the Department of Energy’s Oak Ridge National Laboratory has been working for a decade to develop new manufacturing strategies; BMW has been at the forefront of carbon composite innovation with the help of to industry partnerships, including one with aircraft manufacturer Boeing, that led to its small electric i3 having the most widespread carbon use in a high-volume production car; and longtime carbon fiber aficionado Lamborghini has made news with its “forged composite” process that trims the manufacturing process to a few minutes instead of a few hours.
Progress has been made. In fact, costs in automotive applications have dropped from 35 times the cost of steel several decades ago to just 10 times the price in recent years, according to industry research. But when you flip that thought around and realize carbon fiber costs 10 times as much as steel, it’s still a tough pill for corporate accountants to swallow.
Then there are the sometimes questionable real-world benefits in average road cars, at least relative to the effort and expense associated with the material.
“Carbon fiber has specific properties that benefit certain applications, but their benefit in automotive uses is overrated,” said aircraft designer Philipp Steinbach, creator of the new composite-built Game Composites GameBird aerobatic airplane. “You can’t put the same amount of time and personnel into a production car as you can other applications. Race cars, yes. In road cars, it’s trendy. It sells well and looks great, but whether it’s actually useful compared to the effort is a different story. Plastics and other materials have better properties for cars at much lower costs.”
Of course, dismissing an industry-wide, four-decade engineering obsession as “trendy” may not be fair, given the time-proven benefits of the material.
“The specific stiffness and strength of carbon fiber composites allow automotive engineers to design components with equivalent performance while offering substantial mass reduction over other composite solutions or light metals,” said Patrick Blanchard, technical leader of Ford’s own carbon-fiber cost-reduction effort, most recently manifested in the Ford GT supercar. “Furthermore, using carbon as a reinforcing fiber enables designers to meet stiffness and strength targets within confined design spaces that would not be feasible for glass-based composite solutions.”
Manufacturers are even finding that, under certain applications, the material pays for itself. Acura, for example, chose it for the floor of its own NSX supercar despite its high costs and difficult repair process after accidents.
“It achieves the loading requirements without the need for additional stiffeners,” said parent company Honda’s Shawn Tarr, design leader for the NSX body. “Without the need for the additional extruded stiffeners, and the ability to use recycled, lower cost material, carbon fiber became the lightest weight, lowest cost overall solution for the NSX floor.”
Of course, cars like the NSX and GT are exceptionally pricey applications. And to Steinbach’s point, the arguments against carbon fiber's use are less applicable to performance vehicles; for example, weight management is more critical in aviation than it has traditionally been in automotive applications, save vehicles engineered for track performance. But the logic behind carbon fiber's use in automotive applications has shifted of late. New fuel economy requirements have boosted demand for low-weight materials to help improve efficiency, and electric vehicles jacking up that urgency even more. Carmakers now must pull every lever at their disposal to boost fleet-wide gas mileage.
The question is, can carbon fiber truly be among those levers? Carmakers are increasingly saying both yes and no, advocating for a “right material in the right place” approach that applies as much to an Acura NSX as it does to a Honda Civic—an approach made possible by the steady improvement of alternative composite materials.
“Recent developments in lightweight thermoplastics, like SMCs—a.k.a., sheet-molded composites—can approach the lightweight of carbon fiber with superior surface quality and better manufacturability,” Tarr said. “We used this material for NSX body panels.”
Decisions on materials tend to take a wide range of factors into consideration, he added, from the systems used to join dissimilar materials together—whether it requires adhesive or welding—to the benefits of individual components using multiple materials in different places, either for safety purposes or performance and efficiency benefits. Honda has applied this thinking across its premium and economy vehicle designs.
At Ford, engineers have similarly found that fine-tuning the uses and composition of carbon-fiber-based materials can spread their adoption. “Carbon fiber derivatives and accompanying processes with minimal scrap are the leading candidates for mainstream adoption,” Blanchard said, noting that this applies to carbon fiber composites used in conjunction with both newer plastics and polymers. “Hybrid blends of glass and carbon can also offer a more economical solution, albeit with a trade off in material properties. Other reinforcing fibers such as basalt, are emerging as a middle ground, offering incremental performance over glass fiber without the cost of a switch to carbon.”
But as carbon fiber innovation itself keeps up, it will just as likely stay competitive—though as before, largely at pricey levels. The horse race aspect is perhaps most tellingly revealed in Porsche’s high-performance RS line.
“For the 2016 model year 911 GT3 RS, the car was fitted with a magnesium roof, which was lighter than a comparable carbon fiber roof at the time, and also offered advantages in terms of painting, as carbon fiber needed to be smoothed out more for this process,” said Porsche spokesman Frank Wiesmann. “However, the material and handling advanced in the meantime. We still fit the magnesium roof as standard on the 2018 911 GT2 RS and 2019 GT3 RS, but both cars are available with a weight saving package that incorporates a carbon fiber roof that is even lighter than the magnesium roof, thanks to a new patented sandwich structure. The package also incorporates carbon fiber sway bars and end links for the suspension, and can be paired with optional magnesium wheels.”
But the future of carbon fiber will ultimately rest on whether that innovation trickles down to “normal” cars. Manufacturing times and costs still haven’t reduced significantly enough—industry analysts say it will need to reach $5 per pound, half as much as it is today—and the window of opportunity for that might be closing. A big reason for this: autonomy.
Designer Henrik Fisker, the creator of the serial-hybrid Fisker Karma who is now relaunching his brand with a premium fully-electric sport sedan, says while electric vehicles will benefit from cheaper carbon fiber, the eventual arrival of autonomy could negate that need. As cars will increasingly become specialized, the demands placed upon them for such qualities as crash-worthiness will diminish.
“With autonomous cars and shuttles being used in predominantly urban settings, they won’t need the same sort of structural strength as cars will on high-speed highways,” Fisker said. “If it’s only meant for city traffic and car-sharing, it will require a completely different kind of structure.”
The end result: A car that can use whatever material is most efficient and economical to produce, with less dependence on strength. Lamborghinis and McLarens will still use it for handling and track-lightness, but autonomous people movers will be, well, unmoved by the fancy weaves.