IM7/8551-7 uni-directional prepreg was used for leading edge fabrication. Due to shipping error, the prepreg was exposed to ambient conditions during shipping and possibly partially cured. It was possible to fabricate composite panels and blade test articles with no apparent defects after cure using this material, although it is possible that material properties could have been reduced by the prior ambient exposure. Since the purpose of this work was to evaluate relative performance of a baseline composite to composites with embedded material, it was decided that this material would be suitable for this work.
The purpose of the fan blades on high bypass turbofan jet engines is to accelerate air for propulsion, while a smaller fraction is passed into the compressor section of the engine . At take-off and landing, these fan blades are susceptible to potentially damaging bird strike events that could lead to engine shutdown. As a result, blade impact strength specifications are outlined by the Federal Aviation Administration (FAA) and are prerequisite to blade implementation into commercial aircraft.[1] Meeting the standards set forth by the FAA requires a necessary, but costly, full scale engine test where the pass/fail criteria are dependent on engine size. FAA regulations outline three categories of bird strike: large single bird, small or medium flocking bird, and large flocking bird. For a large single bird, the ingestion speed of the FAA test of turbofan engines currently in service is 200 knots (337.5 ft/s). It is understood that the engine will shut down with the ingestion of a large single bird. Following ingestion of small and medium flocking bird(s) the engine must generate 75% of take-off power or thrust and with only a momentary drop of less than three seconds. For large flocking birds, the engine needs to operate for a twenty minute ‘run-on’. The test to meet these criteria includes evaluation of engine performance at different power ratings until shutdown. These standards affect the design parameters of fan blades.
The IM7/8551-7 pre-impregnated tape was cut according to the ply lay-up designations for each panel . An aluminum mold was custom designed to fabricate the leading edge specimen described in this paper. The mold was a mated 7075 aluminum die, shown in Figure 10, and was fitted with a vacuum pump venting attachment and a channel to capture excess resin flow. All blade coupons were processed in an autoclave following the cure cycle recommended by Hexcel. The cured blades were machined on the
Test data presented in References 3 and 4 provide a comparison between laminate lay-ups and these articles provided the basis for the leading edge design features implemented in this paper.
References 3 and 4 summarize efforts where a simplified blade test article was used to evaluate the influence of variation in composite materials and ply configuration on impact resistance. The fan blades were simulated with a double tapered, diamond shape cross section with thickness decreasing from
The purpose of the fan blades on high bypass turbofan jet engines is to accelerate air for propulsion, while a smaller fraction is passed into the compressor section of the engine . At take-off and landing, these fan blades are susceptible to potentially damaging bird strike events that could lead to engine shutdown. As a result, blade impact strength specifications are outlined by the Federal Aviation Administration (FAA) and are prerequisite to blade implementation into commercial aircraft (Ref. 1). Meeting the standards set forth by the FAA requires a necessary, but costly, full scale engine test where the pass/fail criteria are dependent on engine size. FAA regulations outline three categories of bird strike: large single bird, small or medium flocking bird, and large flocking bird. For a large single bird, the ingestion speed of the FAA test of turbo fan engines currently in service is 200 kn (337.5 ft/s). It is understood that the engine will shut down with the ingestion of a large single bird. Following ingestion of small and medium flocking bird(s) the engine must generate 75 percent of take-off power or thrust and with only a momentary drop of less than 3 sec. For large flocking birds, the engine needs to operate for a 20 min ‘run-on’. The test to meet these criteria includes evaluation of engine performance at different power ratings until shutdown. These standards affect the design parameters of fan blades.
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