REPAIRING SANDWICH CONSTRUCTION
Facing-to-core voids of less than 2.5 inches in
diameter can usually be repaired by drilling a series of
The repairs discussed here are applicable to
holes 0.06 to 0.10 inch in diameter in the upper facing
structural-type sandwich construction, which consists
over the void area. An expandable forming resin, such
of aluminum alloy facings bonded to aluminum
as Thermofoam 607 or equivalent, is then injected
honeycomb and balsa wood cores.
through the holes with a pressure-type caulking gun.
Repairing Minor Surface Damage
When the void is on the lower surface of the panel, only
sufficient resin must be injected to completely fill the
The most common types of damage to the sur-
void. With voids on the upper surface, the core area
face are abrasions, scratches, scars, and minor dents.
should be filled until the resin comes out of the
These minor surface damages require no repair
injection holes. These holes should be sealed with a
other than the replacement of the original protective
thermosetting epoxy resin adhesive, and the entire
coating to prevent corrosion if no breaks, holes, or
assembly cured with lamps, as required for the adhesive
Figure 5-16.--Sandwich construction puncture repair (honeycomb core).