TM 1-1500-204-23-11
Figure 3-5. Heat Lamp Temperature Affects (Sheet 2 of 2)
l. Heat Guns. Many times the complexity of a
temperature control, the temperature control on a hot
surface or the materials being used will negate the
bonder can be used.
use of heat blankets for curing. When a heat blanket
cannot be used to heat the surface of a repair, hot
m. Double Vacuum Debulk (DVD) Tool. The DVD
air may be utilized. For small areas that only need to
tool removes entrapped air (porosity) from wet layup
be warmed, a handheld heat gun may be adequate.
laminates. The inished structural properties of a DVD
Larger areas or higher temperatures require other
produced repair patch are better (lower porosity and
controlled hot air generators. Using a hot air tent
higher iber volume) than a standard vacuum bagged
rather than a heat blanket also assists in controlling
wet layup patch, but not as good as an autoclave
heat loss by conduction as a larger area is usually
cured pre-preg repair. See Chapter 7 for details on
heated than with a heat blanket or lamps. Small,
the DVD process. The resin used in this technique
handheld heat guns can be used to warm resins,
must have a fairly long pot life due to the use of
pre-pregs, and part or aircraft surfaces to improve
heat and the time required to perform the process.
material handling. When using a heat gun, the hot
Hysol EA9390 resin has proven to be one of the few
air should not be exhausted directly on the part or
laminating resins capable of meeting this requirement.
material. To minimize the potential of overheating,
After the dry cloth has been impregnated with EA9390
the part should be heated indirectly. A tent of Mylar
resin, the plies cut, and the plies lat ply collated, it is
can be used to improve heating effectiveness and
debulked using a double vacuum bag debulking tool
evenness. If the heat gun does not have an integral
is placed over the vacuum bag (inner vacuum bag)
3-9