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OCT

19

2011

3 Comments
avatar Category: Automotive

The Case for Composites


, Vice President, Marketing at solidThinking

As noted by my colleague Giuseppe Resta in the last automotive blog post, there was justified fanfare for the BMW “i” brand, yet elsewhere in Frankfurt you could see that steel was not going to go away fast. The production version of the Volkswagen up! was said to be 13 percent lighter than the vehicle it replaced (VW Fox). VW pointed to engine downsizing, high strength steel and component optimization as the keys enablers of this. High-strength and ultra-high-strength steels make up 56.5 percent of the vehicle’s construction and achieve class-leading torsional rigidity. With facts like that, what are the compelling reasons to consider structural composites in the short term?



The auto industry may not use steel as universally as in the recent past – just look at the entire range of all aluminum vehicles offered by Jaguar. However, there is no doubt there is a innovative material supply chain, existing production facilities and the automotive engineering talent to deliver increasingly lighter vehicles of metallic construction for some time to come. But, to take the counterpoint to Giuseppe’s post, what if OEMs soon decide that a disruptive technology is required and continuous improvement has reached the point of diminishing returns? Here are some compelling reasons they might “cross the chasm”:

• The huge weight savings that can be achieved. Parts can be molded at minimum thickness with localized strength driven by optimization. The ability to maintain a constant cross-section over an entire part without the “thinning” of metallic stamped parts increases the ability to manufacture an optimized design.
• Reduction in part count. A complex molding can replace many individual components. Less parts usually results in less BSR (buzz, squeak & rattle) concerns.
• Tooling costs are significantly cheaper, as composite parts don’t need stamping dies. This reduced investment is compatible with lower volume variants of products and shorter-cycle model “freshening.”
• Fewer warranty issues and higher customer satisfaction. Composites will generally outlast steel components due to their corrosion resistance.

Structural composites doesn’t just mean CFRP, but a number of other cheaper fiber-reinforced polymers too. There are many mass production vehicles that use sheet molding compound (SMC) or molded fiber glass. It is interesting to note that one part of the auto industry that uses composites extensively is heavy truck. Freightliner, Sterling, International, Kenworth and Peterbilt have all used composite parts in their cabs for many years.

A great summary of how material and simulation technology are affecting vehicle design was presented by Jeff Brennan at the CAR Management Briefing Seminars earlier this year.

3 Responses to The Case for Composites
  1. avatar mike hinkleman says:

    You fail to address production costs in terms of production rate of structural composites vs metal and the corresponding costs in terms of assembly time. robot or robot-assisted assembly may or may not mitigate those costs. costs of composite tooling are likely greater than that of metal or composite-metal tooling as well.

    • avatar Tony Norton says:

      Thanks for the Comment. The production costs and rate are certainly the most significant issues with respect to adoption in the auto industry, although the cost of tooling can actually be quite attractive for low volume vehicles when compared to stamped parts. BMW have commented that they can offset for the expense of the CFRP BIW in the i3 against the reduce cost of the batteries due to the weight saving. To achieve the expected volumes of around 30,000, along with their partner SGL, they’ve got RTM times down to less than less than 10 minutes a part.

      There is plenty of activity in this area (most publicly from GM, Daimler, VW via Lamborghini and Magna/Canada) in addition to BMW, and structural composites will progress. One commonly held view is that replacement of the cross car beam with a structural composite IP could be the first major application to become commonplace in non-exotic/luxury cars.

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