CompositesWorld

MAR 2017

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NEWS 29 CompositesWorld.com Class A Body Panels Aluminum as target According to a June 2016 presentation by IHS Markit (London, UK) automotive forecaster Michael Robinet, closure manufacture will shift to aluminum from steel by 2022-2023, and then to CFRP and other composites before 2030. is change in materials bodes well for suppliers and fabricators of fiber-reinforced sheet molding compound (SMC). "Our competition in SMC used to be other molders," says Mike Siwajek, director of R&D; at Continental Struc- tural Plastics (Auburn Hills, MI, US), a manufacturer of parts using SMC and other composite materials. "Now we compete head-to- head with aluminum on weight, cost and surface finish." Notably, CSP has received many awards for its low-density TCA Ultra Lite SMC with a specific gravity (SG) of 1.2, in production on the General Motors (Detroit, MI, US) C7 Corvette. Tooling cost for SMC is much lower than for steel or aluminum stamping, offering as much as a 50% reduction. "is gives CSP's molded SMC parts a cost advantage on Class A parts up to 150,000 units per year," he explains. "Above that volume, the cost advantage goes away, but we are still on par with metal." Cost parity at high volume is a powerful asset, says Siwajek. "OEMs are trying to take platforms global vs. having a different model for each continent." Economies of scale are achieved by making the same parts worldwide, and SMC augments this advantage. "For example, three to five dies are required for a stamped steel part," he explains, "but with SMC, only one tool is required, greatly reducing the investment needed for global supply." Another aspect of this trend is to build fewer, globalized plat- forms, but increase the number of model variants, each special- ized to meet different customer demands per region and age group. "For example, in the late '90s/early 2000s, Mustang had five to six different hoods for models, offering styling and performance tweaks, like the Mach 1, the Shelby, etc.," Siwajek explains. "SMC helps to do this very cost-efficiently." "We're also starting to get into different geometries where metals struggle," Siwajek adds, "for example, in liftgates and doors, where we can produce fully assembled components to reduce complexity and weight." One of CSP's initiatives is benchmarking current designs and products, answering key questions: "Where can we save weight and provide value? How can we provide relief where OEMs are having issues?" He offers, for example, a part comprising a magnesium inner and an aluminum outer. "ere are distinct disadvantages to these materials," Siwajek argues. "ey aren't as dimensionally stable, which causes issues during painting and assembly. ey also pose a significant risk for galvanic corrosion." He says CSP is working with multiple OEMs to move away from metal. "Many are afraid of putting SMC through the E-coat process at temperatures above 210°C, thinking that 'plastics' won't handle it. But our TCA parts do that, no problem." State-of-the-art SMC panels The 2016 Jeep Wrangler roof features two Class A surfaces on a single SMC part molded by Continental Structural Plastics (at a rate of 900 parts/day). The company has also reworked a traditional SMC decklid (inset), combining a carbon fiber RTM inner and TCA Ultra Lite SMC outer to cut weight 13% vs. aluminum. Source | Continental Structural Plastics FIG. 1 Fully automated SMC production Aliancys' new SMC line (top) at its Zwolle, Netherlands R&D; facility is shown here cutting carbon fiber bundles onto a foil (center), which are then covered by resin and compressed by belt into the final sheet product (bottom). Source | Aliancys Competing composites SMC, however, is not the only composite under consideration as carmakers pursue multi-material designs for lightweighting. Reinforced thermoplastics and carbon fiber composites also have evolved, though not everyone is convinced of their performance in Class A applications. Michael Polotzki, managing director for SMC compounder Menzolit (Turate, Italy), sees two reasons why ther- moplastics are not as competitive for Class A body surfaces. "First, the thermal elongation is two to three times higher than SMC," he explains, "which makes it very difficult to meet tolerance require- ments, especially on larger parts. Second, the stiffness of the part is not high enough so that you have to add reinforcing structure. is adds cost, weight and production complexity." Polotzki also asserts it is difficult to incorporate ribs and struts into thermoplastic parts without seeing these print through to the visible surface.

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