NASA Langley Research Center has developed a simple mechanism for the clean cutting of high-strength and high-toughness carbon nanotube/poly-mer fiber composites on demand without high blade wear or replacement rates, and related high costs. The cutter is comprised of a set of blades both to score through any resin coating the fibers, and to provide an electrical current to cut through the fiber/composite reinforcement and any remaining resin in yarns, tapes, and sheets.
This technology offers the potential for a very meaningful advance in a critical subsystem area (CNT/composite cutting) in a growing industry. Industry experts recognize the issue as extremely important and one with unsatisfactory solutions for much of the industry, in particular for product manufacturers who turn the CNT/ composite raw materials into products of many varieties and properties. The initial application of this technology addresses a rapidly growing component of the market: 3D CNT printing. In this application, the high strength of CNTs — and especially reinforcements such as yarns, tapes, and sheets — makes them very difficult to cut.
This filament cutting mechanism takes advantage of the electrical conductivity and chemistry of CNT fiber reinforcement to provide a means to achieve clean and precise cuts while utilizing a low amount of energy. The technology employs an opposing set of blades (knives, cursors, or wheels) that serves as both cutter and electrodes, and between which the region of the filament to be cut is isolated. The blades serve to score and degrade any resin coating in the reinforcement fiber, enabling the oppositely DC charged blades to come into contact with the electrically conductive fiber, completing an electrical circuit. This completion of the circuit causes a surge of electrical current to flow through the fiber in the small region between the blades, and thus causes the fiber to rapidly heat up. The rapid heating causes the oxidation of any polymer that is on the fiber surface. Additionally, rapid heating also causes ablation/vaporization of the fiber and/or polymer coating. There is no shearing action required to cut the very strong, tough fibers, which eliminates unintended damage to the fibers due to them being dragged by the blade. Increased blade life is thus an additional benefit. A key aspect of the technology is that it is designed as an in-line, embedded technology for applications such as its initial design goal: 3D printing.