The project ended in late 2019, with the component now vetted for future validation testing within Ford vehicles.
Achieving a Class A Finish
Volkswagen Group of America (VWGoA), another founding member of IACMI, has also worked to rethink its liftgate in composites. According to Hendrik Mainka, project manager at the Volkswagen Group Innovation Hub in Knoxville, Tenn., steel liftgates tend to incorporate a significant number of small components. Producing these using composite materials presents an opportunity to reduce complexity. Fewer parts mean less tooling, which reduces the overall cost.
In 2016, the OEM kicked off a project at SURF to lightweight the liftgate for the Volkswagen Atlas by 30% compared to its existing steel solution. “Our goal was to produce lightweight composite liftgate prototypes for the Volkswagen Atlas in a production-like setting – and we did it successfully in summer 2019 at SURF,” Mainka says.
Through the use of SMC, researchers were able to produce an outer panel with a Class A surface finish and structural inner panels for the liftgate, which were then bonded together to simplify future assembly.
That Class A surface was a significant achievement for VWGoA. Anti-corrosive electrically applied paint coatings (e-coats) are applied to steel car bodies on a standard manufacturing line. In the past, composite surfaces have required a separate, off-line painting process, which slows overall production rates.
VWGoA’s goal was to develop a composite material compatible with e-coats. The team selected SMC because, in addition to its lightweighting potential, the researchers recognized that the material’s excellent thermal stability offered the greatest potential to handle the high temperatures of e-coat paint ovens.
“Technologies like injection molding are not able to withstand these temperatures, while prepreg is not capable of achieving required high volumes,” says Mainka. “At the end of the day, everything comes down to reaching the volume that’s needed and implementing it in the plant without having any changes to the assembly line.”
As Shane Skop, SURF’s composites engineering manager, elaborates, “Typically with compression molding you’re working more with thermoset systems, so you’re getting higher temperature-rated materials, which can withstand automotive e-coat temperatures of nearly 400 degrees Fahrenheit. That’s a big advantage for compression molding over injection molding or thermoplastics. They have a lot of trouble getting through e-coat, which is a major hindrance to widespread adoption in the automotive industry.”
With support from SURF and its material supplier, IDI Composites, VWGoA developed a new Class A SMC and an advanced primer system. Mainka estimates that approximately half the component’s three-year development was spent creating the right material formula to achieve Class A requirements.