Current distribution and capability on carbon fibre composite materials, copper foil and fasteners

This article explores (1) how to carry electrical currents on the
CFRP structure using non-bolted metallic conductors, (2) the
current capability of a fastened junction between an element
representing an A/C skin (CFRP+ECF) and a metallic element
representing an A/C frame and (3) how the AC is distributed
in the presence of fasteners.

For all cases (1)/(2)/(3), tests were carried out; additionally, in
case (3) simulations were also performed.
Precisely, in each (1)/(2)/(3) case, following use case were
tested:
(1) Transferring currents in the internal CFRP structure:
● Use of co-cured and co-bonded copper foil
(2) Current capability of the junction:
● Different countersank fastener installation
(3) Current distribution:
● A test varying the frequency of the AC from 50 to
5000 Hz was performed
Following relevant magnitudes were recorded in the junctions
during the tests:
Figure 1 - Example of installation of metallic strips on A/C
● Electrical resistance
● Thermal elevation for a permanent injection current
● Thermal elevation for a sudden injection of current
● Current distribution among the fasteners
Furthermore, in case (3), simulations have been performed in
order to analyze the behaviour of the current distribution in
the bolts. The simulated model represents the fastened
junction between the skin (metal or CFRP) and a metallic
frame, with a cable running parallel to the skin and
perpendicular to the frame. A current is injected in the cable
to the metallic frame and extracted through the skin.