Helicopter rotor yoke and method of making same

1. A rotor yoke for a helicopter, comprising:

a blade attachment portion;

a mast attachment portion;

an intermediate portion extending between the blade attachment portion and the mast attachment portion, wherein the intermediate portion, the blade attachment portion, and the mast attachment portion define an inner edge, such that the inner edge defines an opening; and

a peripheral, outer edge extending about the blade attachment portion, the intermediate portion, and the mast attachment portion;

wherein both the outer edge and the inner edge include reduced thickness portions exhibiting thicknesses that are less than thicknesses of portions of the rotor yoke adjacent the reduced thickness portions;

wherein the reduced thickness portion extends substantially along an entirety of the outer edge and the inner edge; and

wherein the blade attachment portion, the mast attachment portion, and the intermediate portion are formed from a plurality of loop layers and a plurality of reinforcement layers, the loop layers being configured with a unidirectional fiber roving, the reinforcing layers being comprised of a cross-ply of fibers.

2. The rotor yoke, according to claim 1 , wherein the reduced thickness portion exhibits a thickness that is less than a thickness of an immediately adjacent portion of the rotor yoke.

3. The rotor yoke, according to claim 1 , wherein the reduced thickness portion is frustotriangular in cross-section.

4. The rotor yoke, according to claim 1 , wherein the reduced thickness portion comprises:

a first tapered surface;

a second tapered surface; and

an edge flat extending between the first tapered surface and the second tapered surface.

5. The rotor yoke, according to claim 4 , wherein at least one of the first tapered surface and the second tapered surface exhibits a taper of about 30 degrees.

6. The rotor yoke, according to claim 1 , wherein the reduced thickness portion comprises:

a first tapered surface; and

a second tapered surface extending to the first tapered surface.

7. The rotor yoke, according to claim 6 , wherein at least one of the first tapered surface and the second tapered surface exhibits a taper of about 30 degrees.

8. The rotor yoke, according to claim 1 , wherein the reduced thickness portion exhibits a radius.

9. The rotor yoke, according to claim 8 , wherein the radius corresponds to the thickness of the rotor yoke adjacent to the reduced thickness portion.

10. The rotor yoke, according to claim 1 , wherein the reduced thickness portion comprises:

a first radiused surface;

a second radiused surface; and

an edge flat extending between the first radiused surface and the second radiused surface.

11. The rotor yoke, according to claim 1 , wherein the reduced thickness portion is located in an area of high interlaminar shear strain when the rotor yoke is in service.

12. The rotor yoke, according to claim 1 , further comprising:

a second blade attachment portion;

wherein the intermediate portion extends between the mast attachment portion and the blade attachment portions; and

wherein the outer edge extends about the blade attachment portions, the intermediate portion, and the mast attachment portion.

13. A rotor yoke for a helicopter, comprising:

a pair of spaced apart longitudinal, side portions having ends;

a transverse, central portion interconnecting the side portions; and

a pair of outboard portions interconnecting the ends of the side portions;

wherein the side portions, central portion, and end portions define an outer edge and an inner edge, such that the inner edge defines an opening; and

wherein both the outer edge and the inner edge include reduced thickness portions exhibiting thicknesses that are less than thicknesses of portions of the rotor yoke adjacent the reduced thickness portions;

wherein the reduced thickness portion extends substantially along an entirety of the outer edge and the inner edge; and

wherein the blade attachment portion, the mast attachment portion, and the intermediate portion are formed from a plurality of loop layers and a plurality of reinforcement layers, the loop layers being configured with a unidirectional fiber roving, the reinforcing layers being comprised of a cross-ply of fibers.

14. A rotor yoke assembly, comprising:

a plurality of rotor yokes, fixedly clocked with respect to one another;

wherein at least one of the plurality of rotor yokes comprises:

a blade attachment portion;

a mast attachment portion;

an intermediate portion extending between the blade attachment portion and the mast attachment portion, wherein the intermediate portion, the blade attachment portion, and the mast attachment portion define an inner edge, such that the inner edge defines an opening; and

a peripheral, outer edge extending about the blade attachment portion, the intermediate portion, and the mast attachment portion;

wherein both the outer edge and the inner edge include reduced thickness portions exhibiting thicknesses that are less than thicknesses of portions of the rotor yoke adjacent the reduced thickness portions;

wherein the reduced thickness portion extends substantially along an entirety of the outer edge and the inner edge; and

wherein the blade attachment portion, the mast attachment portion, and the intermediate portion are formed from a plurality of loop layers and a plurality of reinforcement layers, the loop layers being configured with a unidirectional fiber roving, the reinforcing layers being comprised of a cross-ply of fibers.