High-temperature polymer composites (PMC's) offer lighter weight
and higher specific strengths than titanium alloys for advanced
aircraft engine applications-especially in fan and compressor
components, where temperatures do not exceed 550 °F (288 °C). VCAP,
a polyimide resin developed at the NASA Lewis Research Center,
was filament wound at Lincoln Composites in Lincoln, Nebraska,
with graphite and glass fibers to produce a lightweight compressor
case for an Integrated High Performance Turbine Engine Technology
(IHPTET) engine. This engine application requires a PMC that can
withstand air pressures (60 psi) and temperatures exceeding the
degradation limits of other high-temperature polyimides, such
as PMR-15.
In addition to increased performance characteristics, current
commercial and military engine applications require low-cost fabrication
methodologies. Two filament-winding processes were used to evaluate
low-cost manufacturing techniques for the VCAP compressor case:
"dry" powder tow and wet tow winding. In the dry tow
process, a tow of graphite fibers (typically 3000 to 12,000 strands)
is drawn through a bath of resin and then passed through a furnace
to dry the solvent from the resin-soaked tow.
The product of this process, spools of graphite-fiber tow impregnated
with a resin, can be shipped and handled without the safety concerns
associated with hazardous residual solvents. Similar to the dry
tow process, wet winding methods pass a tow of graphite fibers
through a resin bath, but then the wet tow is placed on the tool
used to shape the compressor case. Wet filament winding techniques
are an established procedure for many aerospace fabricators, whereas
dry tow winding is not. Four VCAP compressor cases have been produced,
and the highest quality case was obtained when a wet filament
winding method was used.
Finite element analysis modeling of the VCAP compressor case simplified the design and demonstrated the in situ mechanical and thermal loads for the compressor case. Static rig tests were performed by AlliedSignal Engines in Phoenix, Arizona, to verify the finite element analysis model and build a data base for further engine tests. Finally, the successful combination of NASA Lewis high-temperature polyimides, well-established manufacturing techniques, and the rigorous application of finite element analysis models enabled a 30-percent weight reduction for the PMC compressor case in comparison to the titanium case.
Previous articleLast updated April 30, 1997
Responsible NASA Official:
Gynelle.C.Steele@nasa.gov
216-433-8258
Point of contact for NASA Glenn's Research & Technology reports:
Cynthia.L.Dreibelbis@nasa.gov
216-433-2912
SGT, Inc.
Web page curator:
Nancy.L.Obryan@nasa.gov
216-433-5793
Wyle Information Systems, LLC
