A new fastening technology on the F/A-18 Program in El Segundo will save time and money in assembly, while helping add strength to the airframe without adding weight. Composites technicians and aircraft mechanics are now using “Z-Pin” carbon composite rods to fasten “hats” to the composite skins of select parts in the F/A-18. Hats are one type of stiffener used on an aircraft’s skins to strengthen them while maintaining a minimum weight design.
The Z-Pins are composite fiber rods that act like thousands of nails to connect two composite pieces and create an extremely strong bond after curing. In January, composite inlet duct skins manufactured with Z-Pins were installed for the first time in the F/A-18 Super Hornet center fuselage section. “Z-Pins is one of many F/A-18 affordability initiatives in process to lower the unit cost of the airplane,” said John Kern, manager, F/A-18 Structural Integrity and Test. “We wanted a way to affix hats to the composite structures without fasteners and worked with our supplier to use their fiber rod technology in an aeronautical application. We are the first to use their technology on a production aircraft.” The supplier, Aztex, Inc., holds a patent on Z-Fiber®, a process that inserts a series of rods through composite materials.
It took approximately four years of joint testing and manufacturing development on this new technology by Boeing, the F/A-18 prime contractor; Northrop Grumman; and Aztex to prepare it for use in production on the F/A-18 line. Plans call for the Super Hornet to have multiple skin sections that will utilize Z-Pin bonding. Composites Center IPT leader Tom Hurka said structures mechanics have told him the Z-Pin composites structures delivered to F/A-18 Product Delivery fit very well into the aircraft’s metallic substructure.
“Composites technicians affix the carbon rod tape on uncured structures, and a structures mechanic uses a special tool to insert the rods,” Hurka said. Mechanics complete a 28-hour classroom and hands-on certification process to gain this new skill. Hurka calls Z-Pin a leading-edge method for composite assembly, cutting three to five days off cycle time in structure production.
“Z-Fiber technology is one the biggest innovations I have seen in the composites industry in the last twenty years,” added George Rodgers, manager, ACS Materials and Manufacturing Technology. “It opens up a new world of opportunities for integrated composite structures applications.”
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