Design studies supported by laboratory test data have shown that graphite fiber composite fan blades in subsonic turbofan engines offer significant potential reductions in weight for both the fan rotor and containment structure as well as reduced sensitivity to fatigue failure from foreign object damage. However, substantial progress in the application of composite material technology including mechanical properties, design, development, processing and inspection methods must be accomplished in order to realize these potential improvements over conventional titanium fan blade materials. Turbofan aircraft engines are subjected to foreign object impact by birds, ice balls, ice slabs, rocks, sand, rain, and miscellaneous objects like blown tire treads in addition to operation with inlet distortion. Graphite composite blades must be designed to tolerate these types of damage and still produce power comparable to current engines before they can seriously be considered for flight applications.
In 1969, the General Electric Company selected a high bypass engine as the test vehicle for initial application of graphite fiber composite fan blades. A two phase design, manufacturing and development program was initiated to produce a graphite composite first stage fan rotor suitable for flight application. The first phase of this program, completed in 1970, was directed toward identifying the problems and producing graphite composite fan blades for engine test evaluation with unshrouded titanium blades in the same rotor.
This report presents a status summary of the composite fan blade design, manufacturing and development effort including the results of the crosswind engine testing of these blades at General Electric's engine test facility at Peebles, Ohio.