Influences of contact characteristics of composite fasteners on protection against lightning damage

The high-energy arc generated by lightning strikes seriously threaten the flight safety. When the lightning pulse passes through the contact part of the structure, it will produce arc and spark, resulting in local instantaneous high temperature and raise the potential risk of igniting the fuel tank. In this study, the electrical contact properties and heat conduction characteristics at the contact interface between metal fasteners and composite materials were changed, and the temperature rise, damage and breakdown of composite protective structures under different treatment conditions were investigated under lightning currents with different amplitude and waveform. The influence of different protection design parameters on current conduction path and structural potential distribution is explored.Firstly, the relationship between the contact resistance, pressure and current between fasteners and composites under static conditions is studied by experiments and simulations. By establishing a simple abaqus thermal-electric structure model, it is found that the interface conductivity increases, the stress and strain increase significantly, the interface current distribution and temperature rise tend to be uniform, and the arc is less easy to produce.Based on the test and simulation results, a protective method was proposed to change the contact electrical properties of the filling material between the contact surface of CFRP and TC4 fastener. The electrical conductivity of the contact surface will greatly affect the conduction mode. Filling conductive materials makes lightning flow more smoothly diffuse through the fastener, while filling insulating materials makes lightning flow more evenly distributed throughout the conductive path. The comprehensive effects of contact surface conductivity or insulation threshold, fastener arrangement and wing surface protection layer on lightning current distribution and material damage are explored in this study, which provides a new idea for aircraft lightning protection.