Technology

GMC Made Over 100 CarbonPro Box Prototypes Before Getting It Right

It all has to do with a phenomena named after one of your most favorite snack foods.

When the all-new 2019 GMC Sierra reaches dealers later this year, buyers will be able to option Denali models with GMC’s new CarbonPro bed. Its name is a slight misnomer; the box is mainly made of composites—what you might call plastic or nylon—but that doesn’t mean it isn’t a tough, rugged piece of bodywork. (If anything, a full carbon-fiber bed would likely get damaged a lot easier.) Still, GM engineers had a helluva time getting it right due to a phenomena named after one of your most favorite snack foods.

At the reveal of the all-new Sierra, we had a chance to speak with Tim Herrick, lead engineer for GMC Sierra, who explained the technical challenges of a composite-and-carbon-fiber bed. He and his team experienced the same problem time and time again. In total, Herrick said they manufactured 100 prototypes before perfecting the process. “The first ones we made—and this is a technical term—would ‘potato chip,’” Herrick explained as we both inspected the CarbonPro box. If you can't imagine what this means, let me explain. When potato chips are made, the slices are cut flat then baked or fried. When they're done cooking, they're no longer flat. The chips curl due to the heat.

Just like a Pringle, a similar phenomena was happening with the bottom panel of the CarbonPro beds (there are four panels in all: bottom, two sides, and a back panel that sits against the cab) and Herrick's team was having a difficult time sorting it out. The CarbonPro bed is manufactured in a similar fashion to a traditional metal box. “We heat it up. It comes out of an oven. We pick it up and put it into a press,” explained Herrick. “We press it, form it, then we pick it up very carefully and set it down on a cooling rack.” During the cooling process, the first prototypes 'potato chipped' up to 7 inches.

The riffles in the bed bottom are highly engineered because of this. The radii for the edges and material thicknesses at different points of the riffles were chosen specifically to combat this effect. “We had to recut the tools a number of times,” Herrick explained as we both inspected the CarbonPro box. “When it comes out free form, you want to be able to attach it [without bending it], especially as we don't want a mismatch between the bottom and the sides.” A structural adhesive—not bolts or screws—is used to bond all the pieces together, so having tight tolerances is key with the CarbonPro bed. Otherwise, the pieces may pull apart while the adhesive is curing.

The 2019 GMC Sierra will arrive at dealers later this year. GMC will also reveal another Sierra model later this month in the run-up to the New York Auto Show. GM's truck brand has yet to announce pricing for the new Sierra Denali's CarbonPro bed.

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