Carbon Fiber-Carbon Nanotube Yarn Hybrid Reinforcement

NASA's new material is a toughened triaxial braid made from ductile carbon nanotube (CNT) yarn hybridized with carbon fiber, which is ultimately used as reinforcement material to make toughened polymer matrix composites. The CNT yarn component of the reinforcement is solely responsible for adding toughness, while the processes used to optimize the fiber braiding parameters and tensile properties of the carbon fiber-CNT yarn hybrid tow material determine the overall improvement in tensile strength for resin impregnated fiber tows. Bundles of continuous carbon nanotube yarns are combined with a similar format of carbon fiber, yielding an easily scalable process. Advantages of the material include reduced cost by eliminating use of toughening agents, increased ability to conform to highly complex geometries, greater environmental stability compared to aramid fiber reinforcements such as Kevlar, and possibly decreased density. Many hybrid reinforcements exhibit interfacial compatibility issues, which could lead to premature failure via crack propagation at the polymer matrix interface. In contrast, chemical similarities between the CNT yarn and carbon fiber constituents impart NASA's hybrid reinforcement material with excellent interfacial compatibility. Potential applications include aerospace components, composite pressure vessels, wind turbine blades, automotive components, prosthetics, sporting equipment, construction reinforcement material, and other use-cases where strength-to-weight ratio is of utmost importance. Innovators at the NASA Glenn Research Center have developed a toughened hybrid reinforcement material made from carbon fiber and carbon nanotube (CNT) yarn for use in polymer matrix composites (PMCs). The new material improves toughness and damping properties of PMCs, enhancing impact resistance, fatigue life, and structural longevity. Historically, PMCs have provided insufficient toughness for some aerospace structures. Rubber toughening agents and thermoplastics are often employed to increase material toughness, but such additives increase viscosity of polymer resins and increase processing difficulty and cost. Other reinforcements like aramids exist, but also have inherent issues (e.g., Kevlar absorbs moisture which adds weight and is susceptible to degradation upon UV exposure). NASA's new carbon fiber-CNT yarn hybrid material displays excellent toughness and strength for reinforcing PMC materials while also mitigating issues associated with current hybrid reinforcements like rubber, thermoplastics, and aramids.