New technologies to process carbon fiber and convert it into parts are turning ideas into innovations.
There isn’t a single solution to increase the use of CFRP. The high price of carbon fiber, limited availability in large quantities, lack of options for high-volume/high-speed production, recycling implications and changing OEM mindsets to accept CFRP and associated production requirements are all challenges. However, composites companies are tackling these issues, and industry advances are fast-paced. Here are a handful of new solutions that could potentially impact the entire CFRP supply chain.
Carbon Fiber Oxidation
A simplistic description of carbon fiber production includes three phases: oxidation, carbonization and surface treatment. Oxidation, also known as stabilization, causes the polymer chains to cross link, enabling the microstructure and shape of the fibers to be retained during the carbonization phase. It is a critical step because it takes the most time, energy and expense. 4M Carbon Fiber Corp. in Knoxville, Tenn., is commercializing the world’s first plasma oxidation oven for the oxidation phase of its carbon fiber tow production. The anticipated results are higher production volumes, shorter production schedules and improved energy efficiency.
The new oxidation technology takes less than half the time of conventional oxidation methods, according to the company. 4M is developing its plasma oxidation ovens in partnership with C.A. Litzler, a global manufacturer of process equipment. The ovens will be smaller and use less energy, yet result in greater throughput than conventional ovens, according to 4M. The plasma chemistry, developed by 4M’s affiliate RMX Technologies, generates a highly reactive process that accelerates the oxidative stabilization process utilizing electrohydrodynamics.
Rob Klawonn, CEO of 4M, explained the difference between traditional oxidation and plasma oxidation. “In a conventional oven, filaments are exposed to warm air to chemically change the fiber. But oxygen molecules are quite stable and don’t jump at the chance to react with the precursor,” he says. “Introducing plasma helps excite the atmosphere inside our ovens, making it more reactive than conventional warm air so that more oxidation occurs in a shorter time. Not only is the oxidation time shortened, but the need to recycle the supply air is reduced, further saving energy.”
While 4M won’t reveal too many details about its proprietary plasma oxidation process, Klawonn says it converts precursor material faster, which significantly reduces fiber handling and enables the production of three times as much product in the same operational footprint as traditional carbon fiber production methods. He adds that a wide range of precursors can be processed with the plasma oxidation technology.
In addition, the process can produce 50 percent larger diameter filaments than conventional methods, says Klawonn. “Compression strength tends to be the weakness of carbon fiber compared to glass,” he notes. “The result is carbon fiber tow with high compression performance and buckling resistance. By targeting larger carbon filaments, this weakness can be mitigated while at the same time lowering fixed costs through higher volumes.”
4M anticipates its first product line will be available at the end of 2019, with full commercial production slated for 2021. “By targeting high-volume production, we are resolving a significant barrier to meeting market demand,” Klawonn notes.