Effect of Lightning Currents on Structural Performance of Composite Material 2001-01-2885
High levels of lightning current through carbon fiber composite material can result in local pyrolization of the resin due to heating of the carbon fibers. The loss of resin in the matrix can liberate the fibers resulting in a reduction or “knockdown” of structural performance. The gas produced during pyrolization can also cause delamination of the structural plies, further reducing the structural performance. Two areas of concern are the direct attachment point and fastener locations.
To measure the effect of lightning current on structural performance, two coupon level configurations were employed. One test configuration was a standard, filled hole tension test specimen which had lightning current driven into the protruding head fastener in the center of the part while grounding two edges of the composite material. Different specimens were exposed to four levels of lightning current and then structurally tested for tensile strength. The results were compared to standard filled hole control samples, to determine the relative effect of the various levels of lightning current. The second test configuration evaluated the structural performance of a notched specimen compared to a lightning damaged specimen. An air discharge attachment was made to the center of the test specimen while grounding two edges of the composite material. The width of the damage caused by the lightning current was comparable to the width of a standard notch used to simulate a crack. The standard notch specimen and the comparable lightning damage specimen were structurally tested and compared to determine the relative effect of lightning damage on carbon fiber composite material.