Originally Posted by
57mm
What effect does a lightning strike have on carbon fibre composite structures, if any?
It's more likely to do damage on carbon fiber composites than on aluminum (or other metals). Carbon conducts electricity fairly well, but has a much higher electrical resistance than aluminum (about two orders of magnitude if I recall correctly). This means there is much more local heating due to the strike and hence greater potential for damage.
I don't know about the F-18, but on the 787 there is a copper wire mesh incorporated into the composite layup during build to improve the electrical resistance and hence improve it's lightning protection. I suspect they do something similar on the F-18.
Shortly before I retired, I was observing a flight test on a 767 when we took a lightning strike during our descent to Paine (i.e. Everett). I was in the flight deck observing EICAS indications for my test when it happened - it didn't literally scare the crap out of me, but it came close
Based on the post flight inspection, it attached near the cockpit and exited at the wing root - doing a fair amount of damage to the (composite) wing-body fairing.