Compress & de-bulk lightweight ducts used to transport air in commercial aircraft environmental control systems.
Composite ducts layed up on plaster mandrels require external compression during cure process to eliminate voids in duct walls. Manufacturers’ current process specified the use of a cellophane film, wrapped under high tension, to achieve sufficient compaction. After part cure at a temperature of 120°C, the cellophane stuck to the phenolic/glass prepreg, making removal of the film difficult and adding time to part processing. In addition to the difficulty in removal, the cellophane is a non-shrinking film, which tended to wrinkle the outer layer of prepreg on the part.
Replacing the cellophane with Dunstone 220R allowed the operators to continue wrapping the film in the same manner, with lower tension during tape wrapping.
The shrink characteristics of the 220R enabled the tape to shrink and apply its max shrink force at the same time the resin viscosity is dropping, enabling the tape to minimize resin voids between the plys and reduce prepreg wrinkling.