Core material for balanced rotor blade

A rotor blade sub-assembly comprising:

• a plurality of sub-components;
• and
• a core, wherein in combination, the core and the plurality of sub-components achieve a target weight distribution and moment such that the rotor blade sub-assembly is balanced,
• wherein the core comprises a plurality of cells and an interior of each of the plurality of cells extends between an upper skin and a lower skin;
• and
• wherein the balanced sub-assembly of a rotor blade assembly is manufactured by:
• measuring a weight of the 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 the 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 the target weight distribution and moment for the rotor blade assembly, each cell including a cell opening bounded by at least one cell wall, wherein the cell opening extends between the upper skin and the lower skin, and wherein the at least one cell wall is substantially perpendicular to the upper skin and to the lower skin;
• 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 the rotor blade sub-assembly having the target weight distribution and moment for the rotor blade assembly.