(10) Cover the layup with 4 plies of Style 120
glass breather cloth cut at least 1 inch larger
than the heat blanket that will be used.
Reduced strength will result if the incorrect
(11) Obtain a heat blanket at least two inches
mix ratio is used, if an excessive amount
larger than the largest ply of the laminate.
of air is introduced into the adhesive during
Center over the layup and tape in place.
mixing, or if mixing is inadequate and may
result in loss of structural integrity.
(12) Cover with 2 layers of breather cloth.
Pressure must be applied to adhesive within
(13) Seal the assembly in a vacuum bag. Apply
the pot life of the resin. For ambient temper-
a minimum of 20 inches of mercury vacuum
atures in excess of 90 °F, decrease this time
to the bag.
by 50%. An unsatisfactory repair will result
if the resin gels before adequate pressure is
applied and may result in loss of structural
integrity. Select and prepare a heat blanket
(if required) and all necessary vacuum bag
Failure to properly cure adhesive in accor-
materials prior to mixing resin.
dance with the speciied cure cycle will result in
reduced repair strength may not be detectable
by visual or nondestructive inspection. This
may result in loss of structural integrity.
Apply to part and laminate bonding surfaces
(14) Heat at 35 °F per minute to to the tempera-
ture and time from the system speciic tech-
Failure to observe the correct number of repair
(15) Hold at the temperature for the time from
plies, the correct repair ply orientation, the
the system speciic technical manual or table
correct repair ply overlap and removal of all
7-6. Begin timing when coldest thermocou-
pieces of vacuum bagging ilm will reduce the
ple reaches the minimum temperature toler-
strength of the repair and may result in the
ance. Maintain a minimum of 20 inches of
loss of structural integrity.
mercury vacuum on the vacuum bag.
(6) Apply the laminate containing adhesive to
(16) Cool laminate to below 140 °F with a max-
the part surface containing the adhesive and
imum cool down rate of 5 °F/minute while
scrim cloth. Tape patch in place using lash
maintaining a minimum of 20 inches of mer-
cury vacuum on the vacuum bag.
(7) Cover the layup with the piece of porous
(17) Release vacuum bag and debag part.
release ilm prepared in step (3). Tape in
(18) Perform NDI of laminate and laminate to part
(8) Position at least two monitoring thermocou-
the system speciic technical manual.
ples at the edge of the laminate and tape in
place. (Do not place the thermocouples on
c. Locally Manufactured DVD Tool. A locally
the laminate stack).
manufactured DVD tool can be constructed from
wooden 2 x 4s and 1 inch thick plywood, see igures
(9) Cover the layup with the manually perforated
3-6 and 7-69. The inner vacuum bag must extend
past the wooden box and the outer vacuum bag to
Tape in place.
allow connection of the vacuum port and hoses.