Anew way of creating carbon fibers — which typically are expensive to make — could one day lead to using these lightweight, high-strength materials to improve safety and reduce the cost of producing cars. Using a mix of computer simulations and laboratory experiments, researchers found that adding small amounts of the 2D graphene to the production process both reduces the production cost and strengthens the fibers.
For decades, carbon fibers have been a mainstay of airplane production. If created in the right way, these long strands of carbon-based atoms, narrower than human hair, are lightweight, stiff, and strong — a perfect application for keeping passengers safe.
Carbon fiber sells for about $15 per pound and the team aims to reduce that to $5 per pound by making changes to the complex production process. A lower production cost will increase carbon fiber’s potential applications including cars. Further, the research may lower the cost of producing other types of carbon fibers, some of which sell for up to $900 per pound.
Currently, most carbon fibers are produced from a polymer known as polyacrylonitrile (PAN), which is very expensive, making up about 50% of the production cost of carbon fibers. PAN is used to create 90% of carbon fibers found in the market today but its production requires an enormous amount of energy. First, PAN fibers have to be heated to 200 to 300 °C to oxidize them. Next, they must be heated to 1,200 to 1,600 °C to transform the atoms into carbon. Finally, they have to be heated to 2,100 °C, so the molecules are aligned properly. Without this series of steps, the resulting material would lack its needed strength and stiffness. Adding trace amounts of graphene — only 0.075% concentration by weight — to the first stages of this process allowed the team to create a carbon fiber that had 225% greater strength and 184% greater stiffness than the conventionally made PAN-based carbon fibers.
The team gleaned insight into the chemical reactions taking place through a series of small- and large-scale computer simulations conducted on several supercomputers. They connected experiments of different scales to show that the process works.
The flat structure of graphene helps to align PAN molecules consistently throughout the fiber, which is needed in the production process. Further, at high temperatures, graphene edges have a natural catalytic property so that the rest of PAN condenses around these edges.