What if there was a substance as stiff as steel but just one-fifth as heavy? Well, there is and it’s called carbon fiber.
This plastic-reinforced fabric is a miracle material of the future, one that’s guaranteed to play a large role in the automotive industry. It’s already fairly prominent today, but usage will only increase going forward because its benefits are impossible to ignore.
The Future Today
“We’ve never had a 2,700-pound BMW since model year ’91,” said Jose Guerrero, i-brand product manager at the Bavarian automaker. This German luxury giant’s space-age i3 electric car is a featherweight by modern standards. A major contributor to this impressively modest weight is its carbon fiber reinforced plastic (CFRP) passenger compartment, one of the first in the world.
This firm’s i sub-brand is focused on building environmentally responsible transportation.
“People more and more are buying and purchasing products that align with their belief systems,” Guerrero said. “BMW i means sustainability.”
Underscoring this, an all-electric version of the i3 stickers at 124 MPGe combined and offers an official driving range of 81 miles. For motorists who need more, a version of the car with a small range-extending gasoline engine is also available.
The company’s i division couldn’t deliver on its high-minded goal of environmental responsibility without carbon fiber, which, in the automotive space, has traditionally been reserved for use in ultra-exotic vehicles. But this is changing.
Dave Purcell, executive vice-president of composite intermediates at Zoltek, a firm that’s part of the Toray Group, which is the world’s largest producer of carbon fiber said, “Steel is 50 cents per pound … Zoltek is down in the $6 to $8-per-pound range.” That’s dramatically pricier than its ferrous rival, though he added that historically, carbon fiber costs in the neighborhood of $10 to $12 per pound.
But the elevated price tag of this material can be money well spent. “A carbon-fiber composite is about one fifth the weight of steel,” Purcell said, though that figure depends on the kind or fiber and resin it’s made from.
Taking full advantage of this, BMW has brought numerous innovations to the proverbial table. “We feel like the breakthrough has happened” and carbon fiber is poised to go mainstream, Guerrero said. For them, it’s just a matter of making the production process more efficient and then scaling everything up.
“This whole launch of carbon fiber has been linked with BMW i,” noted Guerrero, but this is only the beginning. “It creates nimble, strong cars that are fun to drive,” core brand attributes for the German automaker, particularly with its M vehicles, which are often dressed up with components made from this material.
BMW’s all-new 7 Series flagship sedan features quite a bit of carbon fiber in its structure, but the company’s i3 and i8 cars are really leading the charge. The former of this electrified duo starts in the $40,000 range. This is a monumental achievement for a vehicle that sells in the volume the i3 does. Guerrero said that last year, they moved at a rate of around 1,000 per month, which is “normal luxury-car business,” not super-exotic stuff like Lamborghini or McLaren.
Space-Age Material
Carbon fiber is a familiar material in military and aerospace circles, but slowly it’s trickling down to the civilian side, a push that’s being led by BMW. “We’re truly the first ones to mass produce CFRP,” Guerrero said.
One of the most famous (or infamous because of its numerous delays) uses of carbon fiber is the Boeing 787 Dreamliner, which is 50 percent composite by weight. Summing it up, Purcell said, “It’s a plastic plane.”
He explained that Boeing engineers went all-in on this advanced material, essentially making the aircraft’s entire fuselage out of carbon fiber, but he said the approach automakers are taking is completely different. “They’re looking at it as a part-by-part basis.” They’re exploring “bolt-on components” that can be used on existing vehicles without totally redesigning them.
To date, BMW has probably been the most gutsy in pushing carbon fiber and Purcell acknowledged that their decision is a bold move. He said other OEMs are “not going to go quite that far.” Not yet, anyway.
Growing Pains
The advantages of carbon fiber are undeniable. It provides tremendous strength and extremely light weight, but these upsides are offset by several negatives in addition to its cost.
“Design and manufacturing are two of the challenges,” noted Purcell. Unlike steel or aluminum, which deform under load, “Carbon fiber doesn’t move until it completely, catastrophically fails.” But Purcell added that this engineering issue can be easily overcome by increasing component safety margins.
Because of its propensity to give up the ghost all at once, Purcell said that predicting how carbon fiber behaves in crashes can be a real challenge, though he added, “BMW is probably an industry leader in that respect.” The company’s i3 has earned a four-star safety rating from Euro NCAP.
According to Purcell, two other major reasons why this exotic material is so pricey are cycle times and scrap rates. “Every piece of [carbon fiber] fabric starts as a rectangle and not every car part is a rectangle,” he said. A resin transfer molding process is just one way components can be made out of carbon fiber, though it results in a 30 to 40 percent scrap rate. “What do you do with all that waste?” he asked. It’s a big problem.
Guerrero said BMW engineers dealt with this challenge by using scrap pieces of carbon fiber in areas of the i3 that don’t require tremendous amounts tensile strength, such as the roof panel.
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Other manufacturing methods can be more efficient, but cycle times are still an issue. Carbon fiber that’s reinforced with thermosetting polymers needs to be baked in an autoclave or similar heat source to cure the resin. “How do you do it quickly, [at] low cost and very consistent?” asked Purcell. It’s something the industry is working on. Amazingly he also said, “We could give them [automakers] the fiber for free and they still wouldn’t be competitive with steel.” According to him, manufacturing time and waste are the two biggest problems.
Another issue hampering the widespread adoption of carbon fiber is recyclability. Understandably, it cannot be melted down time after time like steel or aluminum. Purcell said thermoplastic composites can be reused. However, “The value you’re going to get out of your recycled carbon fiber wouldn’t be near your virgin carbon fiber,” plus, it could cost more to recycle it than it would to manufacture new material, meaning this is not a sensible business plan.
Finally, repair-ability is another major hurdle. “That whole infrastructure needs to be built out,” noted Purcell. “I think your average auto body-repair guy needs to retool.” Fortunately, the process of picking up the pieces following a collision shouldn’t be as difficult as it may seem. Purcell said, “Really you’re just gluing parts back together.”
Along those lines, Guerrero added, “We designed pre-designed cut-zones … so that you can localize the parts repair.” For instance, instead of replacing an entire rocker panel, you could just cut out the damaged area and bond a new section in its place.
Our Fibrous Future
Pricing is an issue with carbon fiber, but manufacturing challenges and scrap rates are arguably bigger problems. Still, companies are innovating at full throttle.
“Zoltek has made some breakthroughs in the cost of the fiber, making it more affordable,” said Purcell. But this isn’t necessarily where advances will come from. “I see more innovations going on now in [the] supply chain converting the fiber, with various different resins, into the final part,” which is where real work needs to be done.
In the future, Purcell sees carbon fiber being introduced in a graduated process, “Where does it economically make the most sense?” He said next-generation vehicles that are due to arrive in the next few years will feature more and more of the material, though they won’t necessarily be completely constructed of it.
Going forward, Purcell thinks OEMs will take a multi-material approach, using things like fiberglass, high-strength steel and even aluminum in addition to carbon fiber. This tactic “allows design engineers to optimize,” to cut weight where it makes the most sense. Concurring with these remarks, Guerrero said, “It’s not a silver bullet that carbon fiber needs to be used everywhere.”
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But when will this material become truly mainstream? Will you ever be able to buy a Toyota Camry made entirely out of carbon fiber? “We’re tackling it head on,” Guerrero said. “We’re learning more and more about it as we’re coming up to scale,” though BMW is keeping its secrets close to the vest. “On the carbon fiber technology, we haven’t shared this with any other automakers.”
Carbon fiber will only grow in popularity as costs continue to come down and manufacturing challenges get addressed. “It’s such an exciting time in the automotive industry,” Guerrero said.
Responding via e-mail, a spokesman for the SGL Group said, “In Moses Lake (Washington) we are building the biggest and most modern carbon fiber production [plant] in the world together with BMW.”
Staying true to their eco-friendly ambitions, Guerrero said this joint manufacturing facility is run by hydroelectric power. Additionally, “We ensured that every step in the process … that we used renewable energy.” BMW’s plant in Leipzig, Germany, gets its electricity from wind turbines.
With investments like this, Guerrero said carbon fiber will be “part of the conversation of building the next-generation of cars.” With lighter weight, greater strength and improved fuel efficiency they’re something we look forward to experiencing.
