TM 1-1500-204-23-11
(c) Vacuum core and sanding residue from
points. DO NOT USE lammable solvents
repair area. Wipe inner skin surface
near open lames. Inhaling solvent vapors
using clean, dry cloth to remove remain-
and mists may cause respiratory irritation.
ing sanding residue. Tape barrier mate-
In extreme cases, exposure can cause luid
rial or release ilm over the area to pre-
accumulation in the lungs and central ner-
vent contamination.
vous system depression. In case of accidental
ingestion, a physician or local poison control
center shall be contacted immediately.
(5) Vacuum core and sanding residue from
repair area. Wipe inner skin surface using
clean, dry cloth to remove remaining sand-
ing residue. Tape barrier material or release
ilm over the area to prevent contamination.
All surfaces must be wiped before solvent
evaporates. DO NOT leave solvent soaked
e. Defect Removal Assessment. When material
cloths on surfaces.
is removed in an attempt to remove a defect, the
part must be re-inspected to verify all the damaged
a. Surface Cleaning Requirements. Prior to the
area was actually removed. Two considerations make
part being processed for repair, the part surface
this necessary. First, most NDI methods, including
must be cleaned and dried to remove dirt, grease,
all ultrasonic and resonance methods, are capable of
aircraft luids, and Nondestructive Inspection (NDI)
inding only irst layer damage. For example, deeper
couplant. This prevents potential contamination of the
delaminations are masked (covered) by the delami-
repair adhesive bondline as well as contamination of
nation nearest the transducer or probe. Thus, after
equipment and facilities. Hand sanding will remove
removing what initially appears to be all the damage
dry contaminants and improve the bonding surface.
present, it is necessary to conirm that no hidden
Whenever possible, sand parallel to the iber direction
defects are present. Second, certain defects tend to
with ine grit sandpaper. Cleaning solvents may
propagate during the material removal operations. For
then be used to remove any remaining contaminants.
example, delamination in a laminate skin may grow
Always refer to the system speciic technical manual
larger during the sanding or grinding operation that
for any particular cleaning procedures.
removes the delamination. Thus, material removal
in the vicinity of the original defect may not ensure
(1) Wiping Cloths. Approved cloths are low
complete removal of all defects. For this reason, it
lint and are tested to contain a minimal amount of
is important to inspect the material surrounding the
contaminates; see Chapter 3 for selection of approved
defect for additional damage prior to patch application.
cloths. Care should be taken to ensure the solvent
of choice does not affect the wipe cloth. Methyl Ethyl
6-5. CLEANING PROCESS. Proper preparation of
Ketone (MEK) dissolves polyester blend cloths and
the repair area before any bonded repair process
most other synthetic blend cloths, leaving a residue
proceeds is crucial in ensuring a quality bond is
on the surface that will affect the bond strength.
achieved. Strength and durability of the bonded
patch will be adversely affected if the repair area
(2) Solvents. Solvents are used to clean an
is not prepared properly. Poor surface cleaning and
area of dust, oils, adhesives, and other contaminants
improper vacuum sealing will greatly compromise the
prior to bonding or painting. See Chapter 3 for
ultimate strength of the repair. This section discusses
selection of approved solvents and cloths. Care
the materials and techniques for preparing composite
must be taken to prevent these solvents from being
and metal surfaces for composite patches. If you
contaminated.
are preparing a metal surface for a composite patch,
you must use special surface preparation techniques
b. Wiping Process. Several applications of the
on the metal; refer to the system speciic technical
cleaning solvent should be used and applied each
manual. In some cases, system speciic technical
time with a clean, dry, lint-free wiping cloth. Clean
manuals may omit the solvent wipe step; this step
an area at least twice the size of the repair. Use
should only be omitted when authorized by the system
one of the following methods:
speciic technical manual or engineering authority.
(1) Method 1. Start from the center of the repair
area and wipe towards the outside. After one pass
has been made, fold or lip the rag so a clean
Use solvents in a well ventilated area. Sol-
area of the rag will be used. Dry wipe before solvent
vents must be used only when wearing
evaporates. Switch to clean cloths frequently. Repeat
approved health and safety equipment. Most
until the entire area is clean before applying adhesive
solvents are lammable and have low lash
or repair plies. Repeat the entire wiping process until
6-10
