High current-carrying capacity study of cnt enhanced composites

The structural components of many aircraft platforms are transitioning from metals to carbon fiber reinforced composites (CFRPs) to achieve lighter weight (up to 80% weight reduction compared to traditional airplanes) and better performance. However, lightning strike protection (LSP) is a major technical challenge for using these materials in aircraft structures in terms of safety and durability, considering a commercial aircraft is struck by lightning strikes on average 1-2 times per year. This is due to the inadequate electrical properties of normal CFRPs, since they lack metal-like high conductivity for LSP applications [1, 2]. This study investigated the use of carbon nanotubes (CNTs) to enhance composite conductivity and explored their basic current-carrying capability. A custom-made test was setup for a current-carrying capability evaluation, as shown in Figures 1 and 2. During testing, samples were exposed at atmospheric condition to high temperatures due to electrical current-induced thermal heating. High electrical currents generated Joule heating causing thermal degradation at over 600°C (main failure mechanism) of the resultant samples. Microstructure changes of the samples were observed using scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis. The results show resin evaporation at the sample notch area and nucleation of Fe and Ti particles. CNTs and buckypapers, which are preformed thin CNT films, enhanced the current carrying capability of the CFRPs. However, performance improvement differed based on the manufacturing method and the types of resin and nanotubes. In addition, higher conductivity of the samples contributed to higher current-carrying density at the breakdown point. These results provided a preliminary understanding of the current-carrying capability and the electrical properties of CNTs enhanced CFRPs and BP composites.