Technical data

13773-001
51-20
Page 730 Nov 2000
(i) Lay-up all remaining repair plies (largest to smallest) using the previous steps as guide-
lines. The remaining repair plies must be staggered from largest to smallest. Each repair
ply must have an even amount of overlap around all edges of the previously installed
repair ply.
(j) Place the second sheet of plastic directly over the stacked and evenly centered repair
plies.
(k) Work out trapped air bubbles and excess resin out from between the plastic sheets with a
squeegee.
Note: The plastic sheets stabilize the materials, preventing distortion.
(l) Wipe up excess resin.
(m) Carefully peel the second sheet away from the last repair ply laid-up on the stack (smallest
repair ply, but first repair ply placed onto the damaged laminate).
(n) Apply a thin coat of mixed resin onto the previously prepared damaged laminate.
CAUTION: Center each ply over the damage. Each ply must have half of the total over-
lap on all sides of the damaged area or over the previous repair ply. The first
repair ply must be 0.5 inch to 1.0 inch larger than the damaged area. Each
additional repair ply must be 0.5 inch to 1.0 inch larger than the previous
repair ply. Place each repair ply in the same direction as the original plies
were positioned. Every other repair ply must have the directional fiber orien-
tation staggered to prevent the repair from warping.
(o) Turn all of the stacked-up plies over together and immediately place all plies over center of
damage.
(p) Carefully peel plastic sheet away from the outer repair ply (largest).
(q) Ensure that each repair ply has an even amount of overlap around all edges of the dam-
aged area and the previously installed repair ply.
(r) Work trapped air bubbles and excess resin out to the edge of the repair and wipe up
excess resin. Ensure that each repair ply has an even amount of overlap around all edges
of the damaged area and the previously installed repair ply.
(s) Lay-up peel ply if required.
(t) Fully cure repair. (Refer to 51-20)
E. Backing Plate
Backing plates are used to repair laminated composites that have puncture damage. The backing
plate can be bonded to the inner or outer surface of the repair area. The backing plate bridges the hole
left by the removal of damaged laminate. Backing plates are constructed from the same material used
for repairing the laminate.
(1) Backing Plate Construction
Manufacture a backing plate to bridge the puncture using Hexcel glass-fiber cloth and Shell
Epon 862/heloxy 68 & Teta 3234 resin system (Type 2 Class 1).
CAUTION: Do not use the MGS L418/418 resin system for manufacturing backing plates.
The aforementioned resin system will not cure at room temperature to a condition
suitable for handling or processing in any manner. At room temperatures this resin
system will only reach an early stage of cure and will be very brittle and easy to
irreparably damage. Do not bend, twist, pull, or push the laminate prior to initial-
cure.