Once the BMW i3 city car rolls from the company’s Leipzig plant later this year, it will represent the very first carbon-fiber car which will be manufactured in any quantity-about 40,000 vehicles per year at full output. The lightweight but sturdy nonmetallic structure from the new commuter car, the effect of BMW’s joint venture with SGL Technologies in Wiesbaden, will mark a milestone in the growth of carbon-fiber-reinforced plastic (CFRP) materials, that have traditionally been very expensive for use in automotive mass production.
CFRPs are engineered materials which can be fabricated by embedding webs of carbon fiber inside molded polymer resins. The fibers bolster the physical properties in the plastic matrix component in the same way that the skeleton of steel rebar strengthens a poured-concrete structure.
Although the i3 electric vehicle (EV) won’t exactly come cheap-estimates run from $40,000 to $50,000-BMW reportedly claims that forthcoming improvements from the production process throughout the next 3 to 5 years should cut carbon composite costs enough to fit the ones from aluminum chassis, which still command limited over standard steel car frames.
CFRP structures weigh half that from steel counterparts and a third below aluminum ones. Add the inherent corrosion resistance of composites along with the ability of purpose-designed, molded components to cut parts counts from a factor of 10, as well as the attract automakers is apparent. But despite the advantages of using CFRPs, composites cost far more than metals, even allowing for their lighter weight. The high prices have up to now limited their use to high-performance vehicles like jet fighters, spacecraft, racecars, racing yachts, exotic sports cars, and notably, the most up-to-date Airbus and Boeing airliners.
Whereas steel is true of between $.80 and $1/kg, and aluminum costs between $2.40 and $2.60/kg, polyester and epoxy resins cover anything from $5 to $15/kg along with the reinforcing fiber costs an extra $2 to $30/kg, according to quality. To enable cars to remove the United states government’s fast-approaching 54.5-mpg average fuel-economy bar, automakers and their suppliers are striving to come up with methods to produce affordable carbon-fiber cars in the mass-scale.
But adapting structural composites to low-cost mass production happens to be a technical and manufacturing challenge, said Ross Kozarsky, Senior Analyst at Lux Research, a completely independent research and consulting firm that targets emerging technologies.
Kozarsky follows composite materials and led a study team that last year assessed CFRP manufacturing costs and identified potential innovations in each step in the complex process.
“Our methodology is to follow, through visits and interviews, the full value chain in the tow, yarn, and grade level onwards, examining the supplier structure as well as the general market costs,” he explained. The Lux team then designed 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 the segments when it comes to sales is ending, Kozarsky said. The wind-turbine business will cope with aerospace for the top market as larger, more-efficient offshore wind-power installations are built.
“It’s more economical to work with bigger turbine blades, which can simply be made using carbon-fiber materials,” he noted.
The Lux report predicted the global marketplace for CFRPs will greater 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. Throughout the same period, interest in carbon fiber is predicted to rise fourfold through 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 large amount of everyone is referring to automotive uses now, which can be totally on the other end of the spectrum from aerospace applications, since it possesses a higher volume and much more cost-sensitivity,” Kozarsky said. After having a slow start, the auto industry will like another-largest average industry segment improvement throughout the decade, growing at the 17% clip, based on the Lux forecast.
The Lux analysis indicates that CFRP technology remains expensive mainly because of high material costs-particularly the carbon-fiber reinforcements-along with slow manufacturing throughput, he reported.
“The industry has reached an appealing precipice,” he stated, wherein industrial ingenuity will vie with all the traditional technical challenges in order to satisfy the new demand while lowering costs and speeding production cycle times.
The best-performing carbon fibers-the higher grades employed in defense and aerospace applications-start off as exactly what is called PAN (polyacrylonitrile) precursors. As a result of difficulty in the manufacturing process, PAN fibers cost about $21.5/kg, according to Kozarsky, who explained that makers subject the PAN to a number of thermal treatments in which the material is polymerized and carbonized because it is stretched. The resulting “conversion” leaves the filaments oriented along the duration of the fiber allow it the ideal strength and toughness. Various post-processing stages along with the surface-acting additives help ensure durability and “handleability.
Kozarsky singled out an industrial/government R&D collaboration at the new Carbon Fiber Technology Facility at Oak Ridge National Laboratory (ORNL), that has been funded with $35 million in U.S. Department of Energy money among the more promising efforts to reduce fiber costs. Area of the project would be to identify cheaper precursor materials which can be processed into good-quality fibers (see “Oak Ridge collaborates for cheaper carbon fiber,”. The program is to test various types of potential low-cost fiber precursors such as the cheaper polymers, inexpensive textiles, some created from low-quality plant fibers or renewable natural fibers for example wood lignin, and melt-span PAN.
Near term the Lux team expects the job that ORNL has been doing with Portuguese acrylic-fiber maker FISIP (majority properties of SGL) on textile-grade PAN to accomplish costs in the pilot-line scale of $19.3/kg in 2013. Although significant, it could be simply a modest reduction if compared to the 50% needed for penetration in high-volume auto applications.
One of the major limitations of PAN, he said, is the fact that “at best 2 kg of PAN yields 1 kg of carbon fiber, that gives that you simply conversion efficiency of only 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 could possibly be achieved by 2017, stated the report.
The Oak Ridge group, Kozarsky said, can also be concentrating on novel microwave-assisted plasma carbonization techniques that can 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 kinds 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 lots of fascination with enhancing the resin matrix at the same time,” with research centering on using thermoplastics as opposed to the existing thermosets and producing higher-toughness, faster-processing polymers.