Overview
tooling for high-volume parts. “A setup time of five minutes will mean buying many more tools than a setup time of one minute in high-volume production,” he said. “Faster resin setup is always better.”
Different Types for Different Applications Auto engineers use different types of composites, including
sheet molding compound (SMC) or bulk molding compound (BMC) formed in fast compression molding, pre-impregnated fibers (prepregs) that are cut and stacked into preforms for compression molding, and woven or stitched fibers (fabrics) that are used in resin-infusion methods. A popular infusion method for composites is resin transfer molding (RTM). SMC uses randomly oriented chopped fibers. SMC tends to be a faster and cheaper method with which to produce auto parts than an RTM process, but it’s usually less strong than the long fibers in RTM that are oriented or woven.
automotive market of 20,000 t per year by 2017. “Tere is going to be a heavy push towards adapting carbon fiber parts for the heavier luxury vehicles, especially to meet the initial 2017 CAFE requirements,” he said. “Tere is willingness to pay a small premium for weight saved, depending on class of vehicle and lo- cation of the part you are making lighter. Parts above the center of gravity or [in] the front of the vehicle matter more.” He believes an ideal application is using the SMC molding
process to fabricate a large single complicated part, replacing several steel parts that need to be fastened or welded together. Te SMC developed with MEI uses chopped fibers, about an inch long, and the material is flow-molded into complex shapes, similar to injection molding processes using pure plastics. “Tese are good for semistructural parts, but if you need a part with greater structural capability, you can combine SMC with localized continuous fiber reinforcements exactly where you need it in the part.”
A further
Automotive front end structure manufactured with Zoltek Panex 35 via direct injection molding. Consolidating parts fastened or welded together with a single, complex CFRP part is an ideal application for CFRP.
While SMC is readily available with glass fiber, now it also
comes in carbon fiber. Magna Exteriors and Interiors (MEI, Concord, ON) and Zoltek (St. Louis), the carbon fiber pro- ducer, introduced an example in 2012. In March 2013, MEI said this best-in-class low-cost carbon fiber SMC material uses Zoltek’s Panex 35 commercial carbon fiber combined with Magna’s EpicBlendSMC thermoset resin formulations. Tey want auto and commercial truck makers to use it in light- weight parts and semi-structural applications. MEI also offers the carbon fiber SMC directly to third-party molders. Zoltek believes the automotive market will eventually be
the largest destination for its carbon fiber, eclipsing current wind energy usage, according to George Husman, Zoltek’s chief technology officer. He said Zoltek is predicting a potential
12 Motorized Vehicle Manufacturing
consideration in future develop- ment of CFRP is the choice of thermoset ver- sus thermoplas- tic resins. Heat cures thermo- sets. Once fixed, they set for all time. Termo- set resins used in automotive applications pro- vide strong, stiff CFRP parts, but are difficult to recycle. Termo- plastics (think heat, squeeze,
and freeze) are tougher and easier to form into complicated parts. “We are developing both thermoset and thermoplastic applications,” said Husman. In general, thermosets repre- sent less risk to manufacturers as they are tried-and-true, producing parts with better heat resistance. “Termoplastic technology offers some unique growth opportunities for very complex parts, using injection molding and compression molding with cycle times of less than 60 seconds,” he said. “Tere are some aggressive technology programs going in thermoplastic right now.”
CFRP Debuting on Body Panels Plasan Carbon Composites (Wixom, MI), is an emerging supplier of CFRP exterior body panel parts. Te company
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