If the BMW i3 city car rolls out from the company’s Leipzig plant later this current year, it would represent the first carbon-fiber car that can be manufactured in any quantity-about 40,000 vehicles each year at full output. The lightweight but sturdy nonmetallic structure of the new commuter car, the result of BMW’s joint venture with SGL Technologies in Wiesbaden, will mark a milestone in the growth of carbon-fiber-reinforced plastic (CFRP) materials, which have traditionally been expensive to use in automotive mass production.
CFRPs are engineered materials that are fabricated by embedding webs of carbon fiber inside molded polymer resins. The fibers bolster the physical properties from the plastic matrix component in a similar manner which a skeleton of steel rebar strengthens a poured-concrete structure.
While the i3 electric vehicle (EV) won’t exactly come cheap-estimates run from $40,000 to $50,000-BMW reportedly claims that forthcoming improvements within the production process during the next three to five years should cut carbon composite costs enough to match those of aluminum chassis, which still command reasonably limited over standard steel car frames.
CFRP structures weigh half that from steel counterparts as well as a third below aluminum ones. Add the inherent corrosion resistance of composites and also the ability of purpose-designed, molded components to cut parts counts by way of a factor of 10, as well as the interest automakers is obvious. But despite the advantages of using CFRPs, composites cost far more than metals, even permitting their lighter in weight. Our prime prices have up to now limited their use to high-performance vehicles including jet fighters, spacecraft, racecars, racing yachts, exotic sports cars, and notably, the most recent Airbus and Boeing airliners.
Whereas steel applies to between $.80 and $1/kg, and aluminum costs between $2.40 and $2.60/kg, polyester and epoxy resins range between $5 to $15/kg along with the reinforcing fiber costs yet another $2 to $30/kg, dependant upon quality. To permit cars to clear the Usa government’s fast-approaching 54.5-mpg average fuel-economy bar, automakers in addition to their suppliers are striving to create ways to produce affordable carbon-fiber cars on the mass-scale.
But adapting structural composites to low-cost mass production has long been a technical and manufacturing challenge, said Ross Kozarsky, Senior Analyst at Lux Research, a completely independent research and consulting firm that is focused on emerging technologies.
Kozarsky follows composite materials and led a study team that this past year assessed CFRP manufacturing costs and identified potential innovations in each step in the complex process.
“Our methodology would be to follow, through visits and interviews, the entire value chain from the tow, yarn, and grade level onwards, examining the supplier structure and the general market costs,” he explained. The Lux team then created a cost model that combines material, capital expenditure, infrastructure, labor, and utility consideration and the chances for cost reductions.
Although the sporting goods, military, and aerospace industries have traditionally developed and first applied composite materials, the pre-eminence of people segments regarding sales is ending, Kozarsky said. The wind-turbine business will cope with aerospace for that top market as larger, more-efficient offshore wind-power installations are made.
“It’s more economical to use bigger turbine blades, which can basically be made using carbon-fiber materials,” he noted.
The Lux report predicted that the global niche for CFRPs will more than double from $14.6 billion in 2012 to $36 billion in 2020, as innovative new production technologies lower carbon-fiber costs-the major cost-driver. Through the same period, interest in carbon fiber is expected to go up fourfold from the current 27,000 million ton (24,500 million t) to 110,000 million ton (99,800 million t).
Major suppliers of carbon fiber include Toray, Zoltek, Toho, Mitsubishi, Hexcel, Formosa Plastics, SGL Carbon, Cytec, AKSA, Hyosung, SABIC, and over 12 smaller Chinese companies.
“A great deal of people are speaking about automotive uses now, which can be totally at the opposite end of your spectrum from aerospace applications, since it possesses a much higher volume and more cost-sensitivity,” Kozarsky said. Right after a slow start, the car industry will like the next-largest average industry segment improvement through the decade, growing at the 17% clip, based on the Lux forecast.
The Lux analysis signifies that CFRP technology remains expensive mainly because of high material costs-in particular the carbon-fiber reinforcements-as well as slow manufacturing throughput, he reported.
“The industry has reached an intriguing precipice,” he explained, wherein industrial ingenuity will vie with the traditional technical challenges to try and match the new demand while lowering costs and speeding production cycle times.
The very best-performing carbon fibers-the larger grades used in defense and aerospace applications-begin as precisely what is called PAN (polyacrylonitrile) precursors. Due to the difficulty from the manufacturing process, PAN fibers cost about $21.5/kg, according to Kozarsky, who explained that makers subject the PAN to a series of thermal treatments where the material is polymerized and carbonized since it is stretched. The resulting “conversion” leaves the filaments oriented along the size of the fiber to give it the ideal strength and toughness. Various post-processing stages along with the surface-acting additives help ensure durability and “handleability.
Kozarsky singled out a commercial/government R&D collaboration with the new Carbon Fiber Technology Facility at Oak Ridge National Laboratory (ORNL), which was funded with $35 million in U.S. Department of Energy money among the more promising efforts to decrease fiber costs. Portion of the project is to identify cheaper precursor materials that may be processed into good-quality fibers (see “Oak Ridge collaborates for cheaper carbon fiber,”. The blueprint is to test various types of potential low-cost fiber precursors such as the cheaper polymers, inexpensive textiles, some produced from low-quality plant fibers or renewable natural fibers like wood lignin, and melt-span PAN.
Near term the Lux team expects the work that ORNL has been doing with Portuguese acrylic-fiber maker FISIP (majority owned by SGL) on textile-grade PAN to accomplish costs at the pilot-line scale of $19.3/kg in 2013. Although significant, it will be merely a modest reduction in comparison to the 50% essential for penetration in high-volume auto applications.
One of the main limitations of PAN, he was quoted saying, is “at best 2 kg of PAN yields 1 kg of carbon fiber, which supplies you a conversion efficiency of just 50%.” Dow Chemical is investigating dexnpky63 polyolefins-polyethylene, polypropylene-since the feedstock because they could offer potential conversion efficiencies of 70% to 75%. If mechanical performance targets could be met, pilot-line costs of $13.8/kg might be achieved by 2017, stated the report.
The Oak Ridge group, Kozarsky said, can also be taking care of novel microwave-assisted plasma carbonization techniques that could produce useful, uniform fiber properties. And ORNL’s nonthermal plasma oxidation process can have the potential to stabilize and cross-link the precursor materials rapidly and efficiently.
Polyolefin-precursor carbon fiber, along with these sorts of alternative thermal-treatment mechanisms, should reduce costs to sub $11/kg at pilot-line scale in 2017, he noted. Kozarsky added that “there’s plenty of interest in improving the resin matrix also,” with research centering on using thermoplastics instead of the existing thermosets and producing higher-toughness, faster-processing polymers.