Core matertal for balanced rotor blade

1. A method of forming a balanced sub-assembly of a rotor blade assembly comprising:

measuring a weight of a plurality of sub-components of the rotor blade assembly excluding a core;

determining, by a processor, responsive to the measured weight of the plurality of sub-components of the rotor blade assembly excluding the core, a configuration of a plurality of cells, based on a weight distribution of the plurality of sub-components, the plurality of cells including a first plurality of cells having a first density creating a first weight in a first area of the core and including a second plurality of cells having a second density creating a second weight in a second area of the core to form the core such that in combination the core having the first weight in the first area and the second weight in the second area and the plurality of sub-components achieve a target weight distribution and moment for the rotor blade assembly, each cell including a cell opening bounded by at least one cell wall;

determining, by the processor, a first anticipated stress in the first area and a second anticipated stress in the second area, the second anticipated stress being lower than the first anticipated stress;

fabricating, via an additive manufacturing process, the core based at least in part on the configuration of the plurality of cells determined by the processor and the first anticipated stress and the second anticipated stress determined by the processor, wherein (1) the second density is lower than the first density and (2) the core is a unitary core; and

assembling the plurality of sub-components and the core to form a rotor blade sub-assembly having the target weight distribution and moment for the rotor blade assembly.

2. The method according to claim 1 , wherein at least one property of the core varies across at least one of a span, chord, and thickness of the rotor blade assembly.

3. The method according to claim 1 , wherein the core comprises a core panel.

4. The method according to claim 1 , wherein determining a configuration of the core further comprises:

determining a weight distribution based of the plurality of sub-components;

determining a weight distribution of the core necessary to achieve a target weight distribution and moment of the sub-assembly.

5. The method according to claim 4 , wherein determining a configuration of the core further comprises:

determining at least one of a shape, density, wall thickness, and material of the core.

6. The method according to claim 5 , wherein the determined at least one of the shape, density, wall thickness, and material is based at least in part on the determined weight distribution based of the plurality of sub-components and the determined weight distribution of the core necessary to achieve a target weight distribution and moment of the sub-assembly.

7. The method according to claim 1 , wherein the configuration of the plurality of cells is determined by the processor based on the weight distribution and anticipated stresses of the rotor blade assembly.

8. The method according to claim 1 , wherein the core comprises a core panel, and the method further includes determining, by the processor, structural and dimensional requirements of the core panel.

9. The method according to claim 1 , further comprising:

forming the plurality of cells, each cell including a cell opening bounded by at least one cell well, wherein at least one cell of the plurality of cells includes end flange connected to a cell wall.

10. The method according to claim 1 , wherein the core is fabricated fabricating the core adjacent to a plurality of integrated fastener locations respectively surrounded by reinforcement zones, the cells in direct contact with the reinforcement zones comprising curved cell walls, and each reinforcement zone in contact with at least one other reinforcement zone via a respective linear cell wall.

11. The method according to claim 1 , wherein the plurality of cells are hexagonal.

12. The method according to claim 1 , wherein the core comprises a core panel, the method further comprising:

determining an optimized configuration of the core panel.