Lightning damage and ignition source study of carbon fiber reinforced polymers composite fuel tank of aircraft

Carbon fiber reinforced polymers composites (CFRPs) are widely used on aircraft because of their superior structural and weight performance. However, compared to conventional metallic components of aircraft, the conductivity of CFRPs is far from satisfying in the case of lightning strike event that may lead to the catastrophic physical damage or ignition of fuel vapor within the fuel tank. So, it is of great value and challenge to produce a total CFRPs fuel tank which can meet all lightning protection standard in spite of its huge out surface area and varied lightning environment. In this manuscript, the lightning effects on a scaled-down model of CFRPs aircraft wing fuel tank with two lightning protection method, laying aluminum mesh and flame spraying alumina are comprehensively investigated. Different combination of lightning current waveforms according to the corresponding lightning zone are exerted to the out CFRPs surface of the fuel tank and the potential safety hazard of which, such as physical damages of surface CFRPs, ignition source of lap-joint structures are detected by visual inspection and nondestructive ultrasonic testing as well as taking photos. The experimental results show that, the two kinds of protecting methods would be effective when relatively moderate currents of lightning zone 2A are injected. However, if more severe lightning currents, namely lightning currents in zone 1B or 2B are injected, the protection effects of these two methods are different and depend on the injecting location on the fuel tank. In addition, the sealant on the fastener or gaps that between fuel tank skin and access doors should be deliberately designed in case of sparks.