U.S. Department of Energy - Energy Efficiency and Renewable Energy
Vehicle Technologies Office
Lightweight Materials Long-Term Applied Research: Magnesium and Carbon Fiber
In the long term, advanced materials such as magnesium and carbon fiber reinforced composites could reduce the weight of some components by 50-75 percent.
Even though magnesium (Mg) can reduce component weight by more than 60 percent, its use is currently limited to less than 1 percent of the average vehicle by weight. Major barriers to its use are:
- High cost and price instability of raw Mg
- Difficult to form a sheet with it at low temperatures
- Low ductility of finished components
- Limited alloy set compared to other materials
- When used in multi-material systems, it is difficult to join, repair, or recycle and has issues with corrosion
The Vehicle Technologies Office (VTO) is supporting a variety of research with INFINUM (a metal production and recycling company), Pacific Northwest National Laboratory (PNNL), the Automotive Materials Partnership (USAMP), and Oak Ridge National Laboratory (ORNL) to overcome these barriers. This research has resulted in a number of improvements:
- Developed new manufacturing processes (sheet warm forming for high volume applications; a extrusion-machining process to produce an ultra-fine grain sheet)
- Developing new and better alloys
- Demonstrated an important type of joint (friction stir-welded Mg-steel joints) needed to integrate Mg components into vehicles more widely
- Created demonstration structures that would allow manufacturers to develop a vehicle front end with a large amount of Mg
- Developed new test methods to characterize how Mg's structure reacts to circumstances similar to those in a vehicle
- Improved methods to prevent corrosion in mixed-material systems
- Developed a new technique for producing primary ("raw") Mg
Carbon Fiber Composites
Carbon fiber reinforced polymer composites can reduce component weight by more than 60 percent. While manufacturers use carbon fiber in high-performance vehicles, the expense of the input material and process to develop it are generally too high for use in popular models.
VTO is supporting a variety of research projects that focus on reducing these costs, with a goal of reaching less than $5 a pound for carbon fiber. ORNL is investigating reducing costs through the use of lower-priced starting materials and improvements in the conversion rate and cost. Zolek is investigating blending a standard precursor for carbon fiber (polyacrylonitrile), with low cost lignin (a chemical compound derived from plants) to minimize cost while maximizing polyacrylonitrile's positive mechanical properties. Similarly, Materials Innovation Technology, LLC is developing low cost carbon fiber composites manufacturing using recycled carbon fiber. The Department of Energy is supporting Materials Innovation Technologies' project, which focuses on structural automotive applications, jointly with funding from both VTO and Small Business Innovation Research funding from the American Recovery and Reinvestment Act.
Together, PNNL and ORNL developed computational tools that help them better predict properties of long-fiber injection molded carbon fiber composites. These tools should help industry accelerate the development of injected molded composites and lower the risk of designing molds that optimize specific properties. ORNL recently opened a new prototype manufacturing facility for carbon fiber with $34.7 million from the Recovery Act. This facility will help validate low-cost manufacturing of carbon fiber using innovative precursors (source materials) and manufacturing processes.