Every year Popular Science rates the crème de la crème in science and technology as part of its annual Best of What's New picks. In the 1999 Automotive Technology section, the editors chose the Chevy Silverado composite truck box as one of the top products, lauding it as "a breakthrough in the use of structural composites":

...this year Chevrolet demonstrated a pickup truck "box" - everything behind the cab - that is lightweight, corrosion-proof, and virtually indestructible. The composite, made from high-strength urethane molded with glass fiber, produces a bed that's stronger than steel. Flexible body panels are dentproof. To be introduced next fall, the pickup box is also a testbed for future composite structures. (See Figure 1.)

Figure 1. Testing to ensure durability where customers need it most.

It sounds almost too good to be true, but hard work and diligence from a team (see links at right) that included researchers from GM R&D made the box a reality. "We found ways to help GM Truck hurdle a lot of barriers to get this into production," says Tom Dearlove, Lab Group Manager, Materials and Processes Laboratory. "Whenever you're trying something innovative that takes a lot of time, effort, and money, it's hard to stay focused and solve all the problems. But we remained committed to the project and produced an exceptional product."

The development team worked together on every aspect of the program: materials development and selection, tool and part design, molding simulations, processing issues, adhesive bonding, painting, repair, and durability. (See Figure 2 and links at right.) The resulting pickup box is not just a run-of-the-mill steel box with an industrial-strength bedliner, but an entire unit made of durable composite materials.


Figure 2. Composite Truck Box Team (left to right): Stan Iobst, Libby Berger, Mark Buffa (Contact Engineer, Engineering Staff), Ray Hodges, Tom Dearlove, Jessica Schroeder, Ed Hagerman (back row), Arianna Morales.

The one-piece inner panel and inside of the tailgate use a structural reaction injection molding (SRIM) process. Placing a glass fiber preform in the mold and quickly squirting in urethane resin produces a stiff part that's durable and tough. Previous work by the Automotive Composites Consortium (ACC) of USCAR contributed to successful use of the SRIM technology in GM's pickup box.

In contrast, the nonstructural outer panels - including the box's fenders and outer tailgate panel -- were molded using reinforced reaction injection molded (RRIM) materials with low levels of glass fibers or microflakes. These materials provide flexibility or "bounce," ideal characteristics for a fender.

To make sure the box could stand whatever it might see in operation, GM Truck engineers put it to the test in some of the worst operating environments in North America. In phosphate and sulfur mines, chemical environments and tar sand fields, they pounded and punished the composite for two years and 1.2 million miles. Temperatures ranged from -40 to 170 degrees F.

Composite Truck Box: Highlights

• Over 1.2 million miles of testing in the most extreme conditions including phosphate mines, tar sand fields and construction sites and at temperatures ranging from -40 to 170 degrees Fahrenheit
• Reduces total weight of truck by 50 pounds
• Molded two-tier loading capability, stake pockets, bulkhead dividers, six cargo tie-downs provide same flexibility as steel box
• Tailgate is 15 pounds lighter than steel, making it easier to open and close
• 1,000-pound load-carrying capability tailgate vs. 600 pounds for GM’s current steel box tailgate
• Protective stainless-steel top-edge tailgate molding provides increased protection for commercial and recreational use
• Structural reaction injection molded inner panels are highly damage-resistant and rustproof
• Reinforced reaction injection molded outer panels bolt/snap on for easy removal, repair, or replacement with minimal downtime

The pickup box withstood this brutal punishment like no other product in the marketplace. But the composite box won't be one-of-a-kind for long - engineers took advantage of the work already done to design the innovative midgate for the new Chevy Avalanche.

"That's the beauty of the composite structure," says Dearlove. "You let your imagination run, configure it a little differently, ask it to do something different, and it works out just fine."

By Diane Kightlinger