3-4. CONSUMABLE MATERIALS.
ilms, and breather are selected to maximize air and
materials are single use products. The following con-
volatiles escaping the repair while also only allowing
sumable materials are used in the repair of advance
a certain amount of resin to leave the patch. Release
ilms allow the bagging materials to be removed after
cure. Peel ply is used for surface preparation for
a. Vacuum Bag Materials. The following para-
graphs discuss selection of materials used in vac-
(2) Peel Ply. Peel plies are used to provide
uum bagging. When selecting bagging materials, the
most important factor is matching material temperature
a surface that is ready for bonding; however, further
capability to the expected cure temperatures. Typical
surface preparation, such as scuff sanding, may be
material temperature capabilities are provided in table
required. The material is peeled from the repair after
3-2. If you have special needs, contact engineering
the repair is cured. Peel plies are manufactured
or the bagging ilm manufacturer for guidance.
from polyester, nylon, Fluorinated Ethylene Propylene
(FEP) or coated iberglass. They can be dificult to
remove if overheated. Some coated peel plies can
(1) General. Vacuum bag materials are usually
nylon materials that form a barrier and isolate the
The preferred peel ply material is polyester which has
composite material from the local atmosphere. Once
been heat-set to eliminate shrinkage and scoured to
this is accomplished and the air is drawn out of the bag
eliminate contaminates. Follow your speciic repair
using a vacuum pump, the earth s atmosphere exerts
guidelines for the selection of peel ply and any
pressure on the laminate (approximately 14.7 psi at
subsequent surface preparation procedures; if in doubt
sea level) which aids in the removal of porosity and
after the removal of the peel ply, scuff sand and
volatiles. Vacuum bag materials must be non-porous.
perform a water break test (refer to the Glossary for
If they are to come in contact with the resin, they
Water Break Test).
must be compatible with the resin system in use.
Several bagging materials are commercially available.
(3) Release Film. Release fabrics and ilms
For most ield repair applications using a 350 °F or
less curing system, nylon ilm of 2 to 5 mils thick is
are also referred to as separator ilm, parting ilm or
suficient. Underneath the bag; the bleeder, release
release fabric. They are sometimes referred to by