ANAHEIM, CALIF. - McDonnell Douglas Corp. takes polymer matrix composites seriously in moving toward lean production. McDonnell Douglas, for in-stance, uses a composite tool to make composite side panels for the AV-8B fighter and is designing a horizontal tail of polymers for the C-17 cargo aircraft.
Composites offer the possibility of large unitized parts, fewer tools and higher performance, Gerald Ennis told attendees of the Society for the Advancement of Material and Process Engineering meeting in Anaheim on March 26. He is the McDonnell Douglas vice president of the Phantom Works prototype center for advanced systems and technology.
``We have reformatted our business'' to transition assembly and process improvements and overcome the composite industry's past ``inability to get our product to the airplane or automobile,'' he said. An effort to reduce the cost of bond tools succeeded on the AV-8B program.
``We went to a metal-arc spray [and] developed a cryogenic process,'' Ennis said.
Technicians prepare an inexpensive polyurethane foam tool, spray on a thin film of tin zinc and apply about 0.375 inch of room-temperature-curing carbon epoxy. ``When it's removed, we have a composite bond tool that appears to be a metal bond tool,'' Ennis said.
Advanced Composites Group of Tulsa, Okla., makes the LTM-10 carbon epoxy.
The C-17 tail development project ``is right on cost at 50 percent,'' he said. ``Maybe the expectation should be 60 percent, but it shows an order of magnitude of change is possible.'' The tail is about the size of a MD-80 wing and, using AS4 fiber and 3501-6 resin, would replace a metal tail.
Other C-17 work seeks to reduce the number of tools. ``For every part, you probably have 2.3 tools'' that require ``lots of people to manage, to deliver, to find, to lose, to expedite, to schedule and to plan,'' Ennis said.
In a C-17 part-count reduction, the company places fiber automatically on part of the 62-foot-long landing gear pods.
``We lay fiber over the top of honeycomb for the inside mold line skin and put [it] in one of those tools with the metal arc coating and go to the autoclave,'' he said.
On March 15, McDonnell Douglas rolled out a prototype of its Delta Clipper DC-XA space craft carrying a composite bismaliemide inner tank that takes all the landing loads and launch loads as well as a composite hydrogen tank, he said.
A new $5 million Ingersoll-Rand Co. fiber placement machine ``takes us away from the hand layup process,'' Ennis noted. ``We put glass in as energy arresters'' and use inexpensive foam tools in producing serpentine ducts.
He envisions carrying fiber from wingtip to wingtip.
``We need to steer fibers around doors and still maintain continuity without ever breaking the fibers,'' he said. ``We will not have wings as in the past; we will have a wing fuselage structure in big pieces with fibers that go from one end to the other.''
Resin and fiber processes will be separated with a $9 million Ingersoll stitching machine with four heads being installed at the McDonnell Douglas facility in Long Beach, Calif.
The resulting one-piece blade stiffener is used to make a skin panel and torque box for a National Aeronautical and Space Administration advanced-composite-technology program.
Stitching cuts inspection ``because you can afford some delam[ination] without any real major problems,'' Ennis said. The structure has no fasteners, is easier to stitch in dry format and uses a resin film infusion process to place resins throughout the product.
In mid-March, McDonnell Douglas unveiled a 28-percent-scale remotely piloted tailless research vehicle that used metal arc spray tools and laser technology with LTM-10 on fuselage skins and IM7/977 on wings.