Numerical study on lightning strike protection method for composite rotor blade based on air breakdown and insulating adhesive layer

The protection effectiveness of traditional Lightning Strike Protection (LSP) for composite rotor blade of helicopter can be diminished due to the explosion risk in overlapping attachment under lightning strike, so a new protection method based on Air Breakdown and insulating adhesive layer (AB-LSP method) was designed to avoid it. In this study, a numerical method was developed to simulate the electrical breakdown, and verified by experiment results. Based on this method, a Finite Element Model (FEM) was established to investigate the effect of two factors (breakdown strength and initial ablation temperature of adhesive layer) on the LSP effectiveness. The results show that the breakdown strength impacts more to the ablation damage in composite than that of high-temperature resistance. Then, another FEM was established to predict the ablation damage by lightning strike in the AB-LSP method protected composite rotor blade. The mechanisms and potential key parameters (magnitude of lightning current, discharge channel location, adhesive layer thickness, and air gap width) that could affect the protection effectiveness were analyzed. The introduction of air breakdown changes the current conduction path and reduces explosion risk. After rational design, this method can offer effective lightning protection for composite helicopter rotor blade and other composite structures.