Optimized composite flexbeam for helicopter tail rotors

Details Optimized composite flexbeam for helicopter tail rotors Optimized composite flexbeam for helicopter tail rotors

1996-07-18

1997-11-25

Kwon, John T.

Fluid reaction surfaces (i.e., impellers)

Articulated, resiliently mounted or self-shifting impeller...

Nonmetallic resilient mounting

B64C 2738

Patent

active

056904746

ABSTRACT:
An optimized composite flexbeam (10) having a pitch region (PR) which includes a core laminate (50) of unidirectional fiberglass material (U.sub.F), and face laminates (52) of unidirectional graphite material (U.sub.G) bonded to mating surfaces (50.sub.M) defined by the core laminate (50). The core laminate (50) and face laminates define an aspect ratio which is greater than or equal to 10 and define chamfered edge surfaces (54.sub.S). Each chamfered edge surface (54.sub.S) defines a critical acute angle .alpha. with respect to the flapwise bending neutral axis (X.sub.A) of the pitch region (PR) and defines a lateral edge (54.sub.E) disposed a vertical distance X from the flapwise bending neutral axis (X.sub.A). The critical acute angle .alpha. is between about 14 degrees to about 22 degrees and the vertical distance X is about 12.5% to about 37.5% of the pitch region thickness dimension (T.sub.PR). The optimized composite flexbeam (10) further includes an inboard transition region (ITR) having a first transition subregion (ITR-1) and a second transition subregion (ITR-2). The second transition subregion (ITR-2) defines a width conic and a critical width transition subregion (Cr.sub.wt). Furthermore, the first and second inboard transition regions (ITR-1, ITR-2) are composed of a combination of unidirectional and off-axis composite materials (U, O) wherein the off-axis composite material (O) defines a percentage %O of off-axis composite material (O) and wherein the percentage %O in the critical transition subregion (CR.sub.wt) is defined by an optimized curve (100).

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