Automotive: The future looks bright for plastics/metal composites

Some 15 years after Bayer obtained a patent for hybrid plastics/metal technology, and six years after the first hybrid parts appeared on series production cars, the use of these composites for structural and semi-structural parts is shifting up a gear.

Not only does Bayer continue to make important technical and commercial breakthroughs of its own, but other technology suppliers are commercializing their own variants, which further adds to the validity of the concept.

Some numbers from Bayer:

To date, some 35 car components have been manufactured using this technology and Bayer materials (essentially nylon compounds) There are more than 20 new automotive hybrid technology projects in development that are set for series production in the next two years By the end of 2003, around 11 million parts had been manufactured using hybrid technology. The first car to incorporate the technology was the Audi A6 in 1998. Now, the latest version of the same car marks another breakthrough. The roof frame, which joins the two sides of the body shell and forms the support for the windscreen, marks the first time that plastics/metal hybrid technology has been incorporated into the Body in White (BiW; the main structural frame of the car). Chosen for weight-saving reasons, the hybrid is around 30% (300g) lighter than the all–sheet metal version it replaces. Costs and performance are much the same. Until now, hybrid technology has been used, in almost all cases, for front-end modules, which carmakers design separately from the BiW. The critical difference here is that the BiW is generally an all-metal structure that is welded together. Fitting a hybrid piece into it is a significant step forward for plastics. This part is relatively simple in its design, and therefore does not make full use of the potential of hybrid technology to incorporate extra functionality—although it does reduce the amount of welding needed. Ralf Zimnol, senior manager for industry innovation at Bayer MaterialScience in Leverkusen, Germany, says the company had to fit in with traditional BiW design thinking, in the same way it did with early front-end designs. Now that the door is open, designs are likely to get more adventurous. "We have been working against 100 years of steel design, so there is not a lot of integration yet," says Zimnol. The part is made by ITM in Nuremberg. Bayer showed the roof frame for the first time at the VDI-K Plastics in Automotive Engineering conference in Mannheim, Germany in March. It also announced that hybrid technology is being used for the first time on a truck—the radiator grille flap on the Mercedes-Benz Actros—and it showed the results of a feasibility study done by Audi that demonstrates the potential for hybrids in cross beams for instrument panels. Bayer is also working on applications in the floor and the chassis. Hybrids in doors have proved tricky. Volkswagen took a license from Bayer to use its technology for part of the door frame of the Golf V, which it molds itself in Braunschweig, Germany. Long-term contracts mean it gets the nylon from another source. A spokesman for VW says that the company is unlikely to use the technology for upcoming vehicles, however, preferring all-metal designs. He says the reason is cost, but it may not be the only one. Zimnol says there are now about 10 processors doing hybrid molding in Europe, three or four in the U.S., and a similar number in Asia. Hyundai and Kia are both making cars with hybrid front ends. Some of the companies in the U.S. are the same as in Europe, though French companies Faurecia and Plastic Omnium make hybrid parts in the U.S., for example. U.S.-based Visteon has been making hybrid parts for the Ford Focus for several years. With Bayer patents on hybrid technology due to run out in the next few years, and with other plastics suppliers and some molders working on rival technologies, Zimnol says the company has to look for more demanding applications for its technology, and also to develop it further. For example, Bayer is looking at hybrids that incorporate several separate pieces of metal. "The front end is now a commodity, so the business is cost driven," he notes. Rivals out for a piece of the pie Other nylon suppliers, notably BASF (Ludwigshafen, Germany) and Rhodia Engineering Plastics (Lyon, France), have been working on alternative plastics/metal technologies for some time, but one key supplier that has been surprisingly quiet on the subject until now has been GE Advanced Materials (formerly GE Plastics). At the VDI-K event, it unveiled a prototype front end for the Nissan Xterra made using what it terms Hydroplast technology, which combines injection molding with hydroformed tubular steel parts rather than sheet. Hydroplast is based on a patented technology called Smartlok , which joins the plastic and metal components of the structure. "We get to keep all the goodies of the steel," says automotive plastics VP Andre Horbach, based in Bergen op Zoom, the Netherlands, citing stiffness, strength, and dimensional stability. The technology is independent of the thermoplastic used, but Horbach says Noryl GTX nylon/polyphenylene ether alloy has a good fit. Smartlok is described as a compound tie between metal and plastic, where the plastic flows through multiple holes in the metal and envelopes the metal from the inside and outside. The development is being led out of the U.S., but is being offered globally. Horbach expects parts to be commercialized as early as late 2005. GEAM is partnering with steel company Variform, and Carlyle Engineered Products (Livonia, MI), which has several molding operations in the U.S. In Europe, the company is working with several tiers on a non-exclusive basis. Horbach says that compared to current hybrids, the GE product needs less plastics, since none is needed to provide stiffening in the steel beam. Total cost can be 20% to 30% less, he claims. Two-step processes have appeal Two years ago, BASF announced a new way to join molded plastic components and sheet metal, called collar forming (October 2002 MP). The plastics and metal parts are joined together by mechanically pressing a collar protruding from the metal component into the plastic component. The company claims that so-called "post-molding assembly" provides more design freedom than inmold assembly, yields parts with better mechanical properties, and places less strict tolerances on the metal component. In the meantime, BASF has further developed the process so that it can be applied to complex parts, with the collars intruding into the molding on more than one plane. The company is now working to improve the speed of the process so that it can be carried out within the injection molding cycle time. Dow Automotive''s premise, meanwhile, is that to get the best stiffness out of the metal component in a hybrid structure, a closed box design is required. It points out in a recent paper comparing various plastics/metal processing techniques, "overmolding of the plastic on a metal insert in the tool forms discrete mechanical connections where the plastic flows through the holes in the metal…the main limitation with this approach is related to the injection molding process. It is not physically possible to form a closed section in a normal tool." Adhesive bonding, on the other hand, "enables a continuous joint between the metal and the plastic and allows a closed section to maximize the moment of inertia and hence the stiffness." Two years ago, the company built a prototype Golf front end using its low-energy surface adhesive (LESA) bonding technology (May 2002 MP/MPI). Pádraig Naughton, global technology leader for Dow Automotive in Schwalbach, Germany, says the biggest hurdle to overcome is the fear in the design community of using adhesive bonding rather than more traditional joining techniques. The technology is new and requires new equipment. However, Dow does not appear inclined to take responsibility for production itself, as it did with adhesively bonded air intake manifolds for Lada (April 2004 MP/MPI). Naughton says production parts should appear on vehicles within five years. Process allows use of PP Hybrids in production today are all in nylon 6 or nylon 66, but Naughton says bonded structures will likely be made in long-fiber-reinforced polypropylene. "We are talking in general about modules mounted after the e-coat," he says, noting that high-temperature resistance is not critical in such parts. Rhodia also offers an assembly solution—several in fact. Under the umbrella title of plastics and metal assembling (PMA), it describes how metal and plastic components can be combined using clips, rivets, and/or ultrasonic welding. The company also offers a variant of overmolding using gas- or water-assist to provide cored-out sections that lend themselves to functional integration. Peter Mapleston [email protected] Driving the global economy Automobile sales are often used as a barometer for the general well-being of a nation''s economy and state of development. That being the case, current sales figures indicate a hesitant recovery in the U.S, relative stagnation in Europe, and a boom in China. After three years of decline in the U.S., industry consultants Global Insight Inc. (Boston, MA) and Morgan & Co. Inc. (West Olive, MI) expect sales will improve slightly this year, up by 3.5% and 2.5% respectively, although Autopolis (London) expects the market to drop 3% as consumer confidence weakens. In Europe, sales fell slightly last year according to German auto industry association Verband der Automobilindustrie, from 12.6 million units in 2002 to 12.5 million units in 2003. While light trucks and commercial vehicles showed marginal gains (.7% and 1.6% respectively), passenger cars dropped 1.6% from 9.8 million to 9.7 million units. In China, automotive growth kept pace with the white-hot expansion of the overall economy, which grew at an annual rate of 9.1% in 2003. After cracking 1 million vehicles for the first time in 2002, sales doubled in 2003 to 2.04 million units. Volkswagen enjoyed the largest market share, selling 694,000 vehicles last year (it has two production JVs in the country with a capacity for 800,000 units/yr and has said it plans to double that by 2008), with General Motors a distant second, at 387,710 units. Honda (123,000), Peugeot Citroen (103,000), Suzuki (100,000), and Toyota (98,000) round out the top six nameplates in China. The growth of the Chinese vehicle market is more than matched by the expansion in the components market, a sign of the growth in local vehicle production. Components are largely imported at this point, according to the China Automotive Industry Information Network. Imports nearly tripled between 2002 and 2003, rising in value from $3.38 billion to $9.47 billion. Tony Deligio Worlds apart Europeans may moan about the price of fuel for their cars, but they have lived with it for a long time. In several countries, diesel-powered cars, which are more fuel efficient, have long been popular because of the lower tax this fuel attracts, and their numbers are growing across the continent as the performance of diesel engines improves—and the noise they make diminishes. Pan-European penetration could reach 50% next year, say some consultants. But in the U.S., where overall fuel efficiency has remained largely unchanged for decades, gasoline hit a record-high $1.78/gal in mid-April (albeit less than half the European price), and consumers are fast changing their habits. One relatively small segment is showing remarkable growth just as new models are being introduced. Hybrid vehicles, which pair a combustion engine with a high-voltage battery-powered motor to offer better fuel consumption and reduced emissions, were mass produced for the first time by Toyota, with its Prius, in 1997. Honda followed with the Insight in 1999, and a hybrid Civic shortly thereafter. The Prius was launched in the U.S. in 2000, but the vehicles made little impact. A redesign of the Prius, however—it''s bigger and apparently better to drive—has paid dividends for Toyota, according to analyst Mark Morgan Cornelius. Toyota sold 3700 units in March compared to 2500 in 2003, and year-to-date sales in April were up 60%. "They''re just now catching up with demand," Cornelius says. "Until recently, you had to be on a waiting list." American manufacturers have been slower to respond, but Ford will be the first entrant this summer when it introduces the Escape, a full-hybrid SUV. "If [Ford] wanted to get there first," Angela Coletti, a Ford spokeswoman said, "we probably would have applied the hybrid technology to the Focus, but we were committed to giving our customers a no-compromise SUV." Ford plans to make 20,000 of the vehicles, which will be assembled alongside its gasoline Escape, in Kansas City, MO. The hybrid Escape has "V-6 like" acceleration according to Ford, coming from its 2.3-liter four-cylinder engine and electric traction motor. Launched at April''s New York Auto show, Ford had a series of celebrities drive nonstop for 37 hours in Manhattan on one tank of fuel to demonstrate the vehicle''s efficiency. In the end, it traveled 576 miles and averaged more than 38 mi/gal. To put this in perspective, that''s about half as good as so-called 3-liter (3 liters of fuel per 100 km) sub-compacts sold in Europe by VW and Audi. To date, hybrids have made little impact in Europe. This is probably due to the strength of diesels and European carmakers—which, to date, have not developed hybrids of their own. Tony Deligio Web-only bonus automotive market coverage Web-only: Combining Thixomolding with injection molding Thixomolding, a way of making alloys of magnesium (and potentially other metal) parts on equipment very similar to plastics injection molding machines, has the potential to usurp both plastics and steel in numerous applications, including automotive. To date, most applications have been small, Japanese, and for IT applications such as laptop computer housings. One reason for this is that until a few months ago, only Japan Steel Works (Tokyo) made Thixomolding machines, and mostly smaller types (the largest is 8500 kN). Stephen LeBeau, sales and marketing VP for Thixomolding licensor Thixomat (Ann Arbor, MI), further notes that while steel prices are rising because of increased consumption in China, magnesium prices are falling-because more is being mined in China. At around $2/kg, it now costs well under half the 1990 price. On a price-per-volume basis, it is cheaper than aluminum. Now that the technology has been proven-Thixomat says more than 260 machines are now in commercial operation-and Husky Injection Molding Systems (Bolton, ON) has developed a version of its Hylectric machine for Thixomolding (it is currently building a 10,000-kN machine and is thinking about even bigger versions), the auto industry is taking a closer look at what the technology offers. Thixomat sees potential for combining Thixomolded metal parts with thermoplastics, either in what LeBeau terms macrocomposites, in which various elements in an assembly could be bonded together, or by overmolding plastics onto metal parts. Processing magnesium and thermoplastics on the same machine is not considered realistic, so the metal part would be made on one machine, and then transferred to another for overmolding. Advanced Elastomer Systems (Akron, OH) says it is developing special grades of its Santoprene thermoplastic elastomer, which chemically bond to the metal for overmolding onto Thixomolded parts, and other plastics suppliers are likely to be eyeing opportunities, too. Web-only: As one door opens, another closes Volkswagen wanted to use outsert molding for the doors on its new Golf, then changed its mind. It is probably regetting the decision. Arvin Meritor (location to come), a systems manufacturer specializing in door modules, window lift systems, locks and sunroofs, and component manufacturer Philips Components (Wetzlar, Germany) recently took up a suggestion made by Ticona (Frankfurt, Germany). The idea was to use the outsert molding Ticona (then Hoechst) invented to produce an automotive door inner module, which separates the wet and dry sides of the door. Ticona says the module offers considerable cost advantages by saving assembly of no less than 17 functional components. In outsert molding a number of plastic functional elements (such as bearings, holders, and guides) can be anchored on a metal baseplate in a single shot. Ticona''s Hostaform acetal copolymer has become the material of choice for the application. On the module, Hostaform is used with a thermoplastic elastomer for sealing components. The companies developed a structural component that would serve as a carrier for the window lift system, lock, and door loudspeaker, among other parts. Fastening elements for the loudspeaker, cable loom, door lock, installation flaps, the leadthrough for the opening rod, and the centering dome for module installation were all incorporated. Ticona says the outsert-molded door module "closes the gap between a conventional, assembly intensive door module with a metal carrier plate and an all-plastics door module." Bernhard Pfeiffer is a group leader for exterior applications at Ticona in Kelsterbach, Germany. He notes that outsert molding has long been used in such automotive components as window lift mechanisms and cassette players, but it has never before been used for a part as large as this panel. He draws a distinction between outsert molding and hybrid molding. "The aim of hybrid molding is to integrate functions; hybrid technology is to increase stability." His argument is that a simple plate design is cheaper to make in metal than in plastics, while functionality can be added with the outsert technique. Ticona went to Arvin Meritor some four years ago after the Tier One received a request from VW to develop a door module for the Golf V (now in production). Pfeiffer says AM was interested in the concept, but had no experience in outsert molding, which is when Philips Components was brought in. The company, part of the Dutch Philips consumer electronics group, has years of experience in the process, especially in production of cassette player carriers. Pfeiffer says the part passed all performance tests set by Volkswagen, but the project was killed when VW decided to go with a new concept for its doors, in order to make it easier to insert the window glazing into the mechanism that moves it. However, the new design has much wider variations in overall dimensions, one reason apparently why early production levels of the new Golf were well below targets. Contact information
BASF   www.basf.com Bayer   www.bayermaterialscience.com Dow Automotive   www.dow.com/automotive/ GEAM   www.geadvancedmaterials.com Rhodia Engineering Plastics   www.rhodia-ep.com