According to this article, composites on the F-35 are used almost exclusively in skin applications. (Below are excerpts from the article. Please read the original for more details)
During the F-35’s SDD phase, production of skin sections has differed, depending on the supplier, the part’s complexity and cost effectiveness. ATK, for instance, uses automated fiber placement (AFP) technology to produce many of the wing composite parts. Lockheed internally chose to produce the forward fuselage skins using hand layup.
At Lockheed Martin in Fort Worth, forward fuselage skins are hand-layed on Invar 35 tooling and cured in one of three large autoclaves built by Taricco Corp. (Long Beach, Calif.). Sacrificial plies cured into the laminates are subsequently machined to control thickness of the skins. At ATK, fiber-placed skins for the wing are cured and, following cure, skin thickness is precisely measured using a process developed by Lockheed Martin’s Manufacturing Technology & Production Engineering personnel. If needed, additional plies are layed up and the entire structure is cured a second time in a process called cured laminate compensation (CLC).
Once the composite skins are molded, trimmed and inspected, they are ready for attachment to constituent airframe structures. This is accomplished with fasteners drilled through the skin and into the frame at predetermined locations. Management and optimization of drilling on the weight-sensitive F-35 has become a significant effort, and part of the SDD process involves evaluation of drills, drilling tool geometry, tool efficiency, tool life, hole-drilling time, cost per hole drilled and other variables.
Born says the substructure provides backing for the skin and, therefore, helps prevent delamination.
