Inside the VW Scirocco, which uses Ticona Celstran+ material for its IP.
“Steel, in particular, has redoubled its efforts,” Paul Spevetz, product marketing manager, Automotive Interior/Exterior for Ticona Engineering Polymers (ticona.com), acknowledges, speaking to the issues of the greater deployment of plastics in automotive applications, particularly on exteriors.
When it comes to interiors, plastics have a solid position. Ticona, for example, has just released in the North American market new grades of a polypropylene (PP) that is reinforced with long glass fibers. The Celstran+ PP LFRT (long fiber reinforced thermoplastic) materials were originally developed by Ticona for use by European vehicle manufacturers for car and truck instrument panel applications. The materials are said to be competitive with SMA (styrene maleic anhydride) and PC/ABS (polycarbonate/acrylonitrile butadiene styrene) blends. Because a pultrusion process is used to develop the material, there is even fiber coating with the base polymer and uniform fiber distribution in the matrix, thereby providing superior stability, as well as a good surface finish, both important characteristics for components like instrument panels. One vehicle that has the Celstran+ is the Volkswagen Scirocco; VW, of course, is well known for the quality of its interior execution.
But one of the big hurdles to greater plastics deployment—even in the interior—is, Spevetz says, the fact that there is a great deal of “accumulated knowledge and lessons learned” among automotive product and process engineers when it comes to steel and less when it comes to plastics. Speaking to an interior application, he notes that in one instance there was consideration of removing some of the metal from seating systems in order to help reduce vehicle mass. “But the crash loading data that is out there about the steel structures for seats is so well understood, that the idea of replacing it with polymers . . .”
But the changes that the auto industry is presently undergoing may make the deployment of polymers more likely to occur. For one thing, there are issues related to achieving Corporate Average Fuel Economy (CAFE) standards; by 2016 the standard calls for 35.5 mpg, which is 40% above where they’re currently at. One way of achieving better fuel efficiency is through reducing mass, which plastics can contribute to.
For another thing, given that there has been a considerable downsizing of engineering staffs at both OEMs and suppliers—retirements and buyouts of veteran staff are big factors in the headcount reduction—there is the possibility that as younger engineers are brought into the companies there will be less reticence to try new things—like plastics in areas where they’ve heretofore found limited use—for the simple reason that they don’t have the same comfort and familiarity with the traditional materials.
One way that some new ideas are being brought into auto, Spevetz says, is by having people from non-automotive companies coming in and talking about what they’ve done. An example: “How you join materials—where polymer and metal come together—has historically been a weak link,” he says, adding that this is a place where “a lot of white-sheet thinking” is required. “Sometimes, we bring in people from outside automotive in order to show how they’ve handled high-stress integration between traditional steel and polymer components so that the design takes the force away from where the materials come together.”
Another example relates to the concern with the growth—or thermal expansion (and contraction)—of plastics. Spevetz says that people from aerospace have explained how they use dimensionally stable polymer components on the leading edges of the wings on commercial aircraft.
It can be done, but it takes some different thinking.
If we put knowledge aside, then another factor is the cost associated with materials, be they polymers, steel, aluminum, or magnesium. The issue here is the level of cost effectiveness of the various materials in the applications. The cost is not just associated with the material itself, but with the surrounding infrastructure. For example, stamping plants are certainly common in automotive as the industry is pretty much predicated on steel. To make the switch to plastics, Spevetz acknowledges, would necessitate a change of tooling and equipment, almost a “wholesale shift.”
Still, as time to market becomes more important, as does a wider-range of low-volume production of niche products, polymers become more viable.
Spevetz says that they’re working with both boutique builders who are looking at using engineering polymers for extreme performance vehicles and companies that are interested in creating low-cost plastic vehicles. Both ends of the spectrum, as it were. And he thinks plastics are up to the challenge.—GSV