In conjunction with several universities and testing labs, the plastics industry has developed process modeling for injection molded long-glass-fiber composite parts.
The technology may open the door to greater use of such materials in semi-structural automotive applications and other areas where strength and stiffness are critical.
“This will allow you to use plastics in places that companies have never thought of using plastics before,” said Marianne Morgan, automotive industry manager for engineering plastics for BASF Corp. of Florham Park, N.J.
Long-fiber applications are growing but are still limited because tooling needs to be developed so prototypes can be produced to assess potential parts' mechanical properties.
The new process modeling, and the research backing it up, will enable companies to bypass “the make it and break it,” trial-and-error testing on plastic parts that could have delayed the adoption of LGF-filled plastics for years, said Mike Wyzgoski, a consultant to the American Chemistry Council's automotive team.
“I think all of the properties — the stiffness, the strength, the impact resistance and the toughness of the parts — will improve” with the use of long fibers, “because of the way the fibers are oriented,” Wyzgoski said in advance of his April 24 presentation on predictive engineering at the Society of Automotive Engineers World Congress in Detroit.
Wyzgoski is a former research and development group leader at General Motors Co. and former polymers group manager for Delphi Research Inc.
The process modeling is now available, in a drop-down menu, to product-development engineers through Moldflow simulation software from Autodesk Inc., for example.
Engineers can use data from the research to see how glass fibers are affected by the molding process, and how the molding will affect the finished part. That is critical information because the flow of long fibers is very different from the flow of short fibers through the gate and mold, Wyzgoski said.
With the software, toolmakers can determine, for example, where to position the gate.
Long-fiber composites offer improved properties over short-fiber composites, he said.
“Stiffness and strength increase by a factor of two, and impact resistance by a factor of five to 10,” Wyzgoski said. “With fatigue or creep, you could be looking at orders of magnitude of improvement of 1,000-10,000.”
That could open the door to replacement of short-fiber composites in some applications, and metal replacement in others.
Mercedes-Benz, for example, already has a carbon-fiber wheel rim.
Another European carmaker, Audi AG, plans to roll out by the end of the year fiberglass-reinforced epoxy road springs for its electrically propelled Audi R8 e-tron model. The springs match the performance of steel coils for load bearing, but are around 40 percent lighter. The spring's core consists of long glass fibers twisted together and impregnated with epoxy resin. A machine wraps additional fibers around the core — which is only a few millimeters in diameter — at alternating angles of plus and minus 45 degrees to the longitudinal axis.
The fiberglass-reinforced suspension springs also will be introduced on some 2013 Audi midsize and large luxury models.
Some of the other potential automotive applications, Wyzgoski said, are front-end modules, instrument panel retainers, substructural components and body panels, and car jacks.
“They can be used for many semi-structural applications and will help reduce weight as opposed to using metals,” he said.
In addition, Morgan said there is a lot of focus on developing crash-absorbing automotive parts and crash-resistant seat structures from such composites. They could also be used for battery trays in hybrid and electric vehicles, she said.
Beyond autos, long-fiber composites could be used in sports and recreation applications, casings for power tools and outdoor equipment such as lawn mowers, farm equipment, tractor hoods, and seating and substructures in boating, Wyzgoski said.
“A lot of companies don't want to build a tool because it is a pain. This allows you to do that predictive modeling on a computer and put in the needed geometries,” he said. “This is the key and the first step to properly predict the properties.”
“The ability of automotive engineers to dependably predict the modulus, impact strength, fatigue and stiffness of various-sized long-glass-fiber-reinforced thermoplastics depends on reliably modeling the fiber sizes, the fiber orientations and the relative fiber positioning with each part,” he said. “Oak Ridge National Laboratory and Pacific Northwest National Laboratory have validated that these three vital components can be predicted by process models for long-glass-fiber-reinforced plastics.
The other long-fiber research partners include Michigan State University, Virginia Tech, the University of Dayton Research Institute in Ohio and the University of Illinois. The research was funded by the Department of Energy.
“Without knowing these three crucial components, we cannot move on to create models that predict mechanical performing modeling,” Wyzgoski said. “This allows accurate mechanical performance predictive modeling to occur for the first time” for long-glass fibers in the plastics industry.
Morgan agreed. “This is key because if you can't model it and have predictive behavior, North American auto companies won't do it.”
“This is going to give companies confidence that they can build something like they predicted they could build it,” Wyzgoski said. “It lets them get predictive engineering upfront so that parts are doing exactly what they predicted they would do.”
The decision to switch materials for automotive parts will come back to weight and especially cost. “Weight has more value than it used to, but it is still cloudy in the short- and midterm,” she said.
“The weight reduction will get their attention first, but the cost will be the attractive element,” Wyzgoski said.
“Lightweight materials with predictable strength are essential to producing more fuel-efficient cars for the 21st century,” said Steve Russell, vice president of plastics at Washington-based ACC.
“Continuing research like this [will help] global automotive companies utilize plastics, composites and other lightweight materials which can help meet that goal,” he said.