Mansplaining composites

We had some friends over for dinner the other night. They’d read about the recent rollout of Boeing’s 787, heard that these marvelous “composites” were used extensively on the plane, remembered that I edited a composites magazine and started quizzing me about what composites are. This was exciting: As the editor of a trade publication serving a niche of the manufacturing industry, it’s not often that I interact with people outside of the composites world who demonstrate even an inkling of interest in what composites are, much less comprehend that there might be a publication devoted to its coverage.

When moments of keen interest like this come along, one must be alert to hang on and enjoy them for as long as possible. I gave my friends a quick-and-dirty lesson on the carbon fiber technology used on the 787 and reviewed all of the benefits the material conveys to the plane.

Apparently still harboring interest, and mindful of the steep, upward trend in gasoline prices, my friends then asked why this great composites technology couldn’t be applied to automobiles. First, I said, composites are already hard at work in many vehicles, but not to the extent they are in aircraft. I explained some of the economics of the situation — that airplanes are designed to provide decades of service and that only a few hundred are made each year by a company like Boeing. Given this and the cost amortization opportunities offered to airline customers, it makes sense to apply carbon fiber to the fuselage of a commercial aircraft.

Automobiles, on the other hand, are designed to provide a much shorter service life, and it’s a relatively rare vehicle that is maintained in operable condition for more than 15 years. Further, there are about 17 million cars and trucks sold in the United States each year, which radically alters the economies of scale vs. the aircraft model. Automobile parts and components are produced in massive quantities that make them more akin to a commodity. And in a commoditized environment, cycle time matters. This is where widespread use of composites in vehicles gets hung up — but only hung up. That widespread use is a matter of “when,” not “if.”

As several stories in this month’s issue show, the use of composites in cars and trucks is far from a settled proposition. Materials are evolving and maturing, and molding processes have become faster and easier to control. The benefits of composites increasingly outweigh their cost. A case in point is the electronic throttle control profiled in “Engineering Insights” (see “Related Content,” at left). The complex engine component was injection molded from polyester bulk molding compound (BMC), which replaced heavier die-cast aluminum in the design and beat out pricier injection molded thermoplastics (like PPS) because of its ability to withstand underhood temperatures and its greater dimensional stability — and did so at a cost lower than the aluminum original.

Shift gears, however, and you’ll find two stories this month (see “Related Content”) covering the evolution of glass mat thermoplastics (GMT) and long fiber-reinforced thermoplastics (LFRT). These two material types have been bumping up against thermoset composites — and each other — for years. While LFRT is seeing greater growth of late, both have enjoyed a rich automotive history. One of the most appealing aspects of these two materials is that they are more easily recycled and reprocessed than thermoset composites, which will be a critical concern in new car designs going forward — particularly those sold into Europe.

Which brings me back to my dinner guests, who ended their five-minute foray into the world of composites with a simple question: Are these materials recyclable? Well, yes and no — I started to explain the difference between thermosets and thermoplastics. And that’s where I lost them. It was fun while it lasted.