The effect of local copper mesh geometry on the damage induced in composite structures subjected to artificial lightning strike

Abstract

Artificial Current Component A lightning strike tests were performed on three different types of composite panels. Panels of type A were not equipped with lightning strike protection; panels of types B and C were protected against lightning strike with two different types of copper mesh. The measured back surface velocity of the panels seems to be proportional to the peak current normalized with the panel weight. Post-test inspections revealed extended delamination inside panels of type A. For panels of types B and C no delamination was found. Panels of type B and C showed characteristic circular smuts on the impacted surface as well as diamond shaped evaporation of the copper mesh. For panels of type B, the dimensions of the copper evaporation were significantly larger than for panels of type C. it was also found that the orientation of the evaporation zone seems to be related to the geometry of the copper mesh. Multi-physical simulations considering the electro-explosion of the copper mesh were carried out in order to assess if the shape and extent of the evaporation zone could be traced back to electro-explosion of the copper mesh. The predicted damage correlates well with the inner damage zone, but is not able to reproduce the full amount of copper evaporation.

On the Relationship between Lightning Strike Parameters and Measured Free Surface Velocities in Artificial Lightning Strike Tests on Composite Panels

“…The material used in [16] was the Aerospace grade CFRP prepreg material AS4/8552 distributed by Hexcel. Several types of panels were produced with quasi-isotropic stacking sequence (0/45/90/-45) 2s .…”

“…Two kinds of data are analyzed: the total pre-test weights of the panels and the pre-test weights of the protection. This form of data analysis differs from [16], where the electric current was normalized with the total panel weight only. This approach was selected in order to separate the effects of total panel weight and the weight of the copper mesh.…”

“…This approach was selected in order to separate the effects of total panel weight and the weight of the copper mesh. If the same normalization had been chosen as in [16], data for the unprotected panels would go towards infinity for the case of normalization with the weight of the copper mesh (division by zero). By inversion of the fraction, this problem is suppressed.…”

“…The measured peak currents and maximum back-surface velocities reported in [16] are summarized in Table 1. The recorded peak velocities are on the order of several tens of meters per second (35.6 m/s to 86 m/s), which is in line with test reports by Karch et al [20].…”

“…Also, it remains unclear if the backsurface velocity can be correlated to the extent of damage observed in the composite panels. This manuscript therefore analyzes the relationship between the peak current of the artificial lightning and the measured back-surface velocity based on experimental data presented in [16]. If a correlation can be found, this could be a first indicator that the mechanical forces affect the back surface velocity.…”