TM 1-1500-204-23-11
K-Cor requires an adhesive to bond the core to
the face sheets similar to a traditional honeycomb.
(EMI). Fiberglass is not conductive at all and car-
bon iber is not conductive enough. Lightning strike
protection is to prevent a catastrophic failure of the
composite. The most likely electrical material that will
require repair is the lightning strike mesh. However,
electrical grounding of avionics to the structure or
modiications to install new antennas may also require
these materials.
a. Lightning Strike Protection. Lightning strike
materials are typically an expanded perforated foil or
ine mesh of copper or aluminum. While aluminum is
considerably lighter than copper, it is not galvanically
compatible with carbon iber. The additional protec-
tive layers that are required to isolate the aluminum
from the carbon make copper the preferred choice.
Aluminum wire mesh is commonly used on iber-
glass components. In some instances, a conductive
paint or a metallized iberglass pre-preg, such as
1
When removing damaged X-Cor
ThorstrandTM, is used in manufacturing for lightning
and K-Cor, the same techniques
strike protection. Lightning strike protection is typically
are used when removing honeycomb
measured in pounds per square foot. Be very careful
except that embedded X-Cor pins
handling the mesh as it is easy to tear and damage
must be removed from the face sheet
it.
with a pair of pliers.
Repairing X-Cor and K-Cor use
2
the same procedures as other sand-
wich parts. X-Cor can be repaired
DO NOT use aluminum lightning mesh on
with a pre-cured foam sheet or tra-
carbon iber composite structure.
ditional honeycomb.
K-Cor can
be repaired with K-Cor or honey-
b. EMI Shielding and Electrical Grounding. Any
comb. Pre-cured foam usually does
electronic components that must be grounded to the
not have the properties required to
aircraft may also require provisions in the composite
repair K-Cor.
structure. Electrically conductive tapes may be applied
Since X-Cor and K-Cor pin orien-
3
installed on the exterior of the aircraft. Conductive
tation and number of pins can be tai-
adhesives may also be used to connect composite
lored to a speciic part design, like the
components to existing airframe components. Prior
ribbon direction in honeycomb, they
to bonding, the metal components are conversion
do have an orientation requirement.
coated to promote adhesion while permitting electrical
4
Replacement cores for one part may
that an electrical path between carbon and aluminum
not be applicable to other parts on
is avoided which will corrode the aluminum. Refer
the aircraft with X-Cor and K-Cor.
to the system speciic technical manual for detailed
Always refer to the system speciic
electrical grounding requirements. In metal aircraft,
technical manual for replacement
the structure provides shielding to protect avionics
core selection.
and other electrical components from EMI. Composite
components generally provide shielding through the
4-11. LIGHTNING STRIKE PROTECTION, ELEC-
lightning strike protection. Extensive damage to the
shielding may require repair even if the structure does
ELECTRICAL GROUNDING. Since composites do
not. Some systems use electrically conductive tape
not conduct electricity like metals, additional materials
for battle damage and repair of composite components
are required to protect against lightning strikes and
just to address EMI for the electronics.