Carbon-fiber composites offer a variety of advantages for car and truck manufacturers, including lighter weight, better corrosion resistance and higher impact strength than aluminum and steel. They also offer engineers greater design flexibility and allow them to significantly reduce the number of parts in assemblies.
Composite materials weigh about one-fifth as much as steel, but are comparable in terms of stiffness and strength, depending on fiber grade and orientation. They have the potential to reduce vehicle weight by more than 50 percent.
However, the drawback to composites is their steep price tag; they currently cost much more than steel. Carbon-fiber parts also take longer to produce than traditional steel stampings, which can be punched out in seconds.
Engineers at Michigan State University’s Composite Vehicle Research Center (CVRC) are tackling those challenges head on.
Composites research is nothing new at Michigan State. In fact, the school has been studying the topic for more than 25 years. However, until recently, most activity has focused on aerospace and military applications.
“The main driver for our work now is based on lightweighting activity in the auto industry,” says Martin Hawley, Ph.D., a professor of chemical engineering and materials science who serves as the CVRC director. “We operate in conjunction with the College of Engineering’s Composite Materials and Structures Center, which is a multidisciplinary research facility.
“The CVRC is a center of excellence for the research, design and implementation of composites for lightweight, durable, cost-effective and safe vehicles,” adds Hawley. “Our research efforts include both passenger vehicles and heavy-duty trucks.”
The CVRC is housed in a 20,000-square-foot off-campus location. It includes 10 faculty and 25 graduate students who are working on a wide variety of projects. Most activity is focused on carbon-fiber composites in general, and body and chassis components in particular.
The facility features a state-of-the-art lab for testing strength, impact and fatigue characteristics of composite materials. Engineers are also developing new production processes using low-cost, non-autoclave methods, such as vacuum-assisted resin transfer molding (VARTM).
“In the VARTM process, dry, net-shape fibrous textile reinforcements are infused with a liquid resin and cured in a single step to produce a structural part,” explains Hawley. “Instrumented tools are being designed and fabricated for model verification and the manufacture of prototype composite structures.
“VARTM will allow automakers to make more complicated parts that can simplify assembly by reducing parts count,” adds Hawley. “The big challenge is how to do that in a high-speed way that is cost-effective and viable.”
Hawley and his colleagues are also developing simulation models to analyze temperature and pressure variations. The goal is to provide a better understanding of how composite materials are affected by the thermal, chemical, physical and mechanical processes that occur during fabrication.
“New types of composite joining techniques are another important focus for us,” says Hawley. “Joints, whether mechanical, adhesive or hybrid, are critical to the performance of composite structures, because they transfer high loads even as they create significant stress concentrations. Structural failures usually originate at joints.
“We study bolted joints, because of their widespread application to thick composite sections,” adds Hawley. “Design and optimization of joints requires creative thinking, complex numerical analyses and extensive experimental validations. We conduct three-dimensional static and dynamic finite element analyses, coupled with novel experimental methods for validation.
“In addition, we’ve patented some adhesive bonding techniques,” Hawley points out. “We expect that to become the primary composite joining technology in the future.”
Michigan State is also leading the light- and heavy-duty vehicle component of the Institute for Advanced Composites Manufacturing Innovation, which is a $70 million federal program being spearheaded by Oak Ridge National Laboratory.
And, the school is currently in the process of establishing a new prototyping facility in downtown Detroit. "When it opens later this year, the lab will help us transfer some of the composite technology we've development on campus directly to the auto industry," says Hawley.
To learn more about how engineers at Michigan State are developing new adhesives for carbon-fiber composite joining applications, click here.