CMC Rotor Blade Root Attachment with Sacrificial Datum Machining

The patent applies preliminary action by pre-forming the root region with an oversized geometry that includes built-in datums and attachment fillet radii during the CMC manufacturing process itself. This preliminary formation of precise geometric features eliminates the need for subsequent machining that would cut through critical composite plies, thereby maintaining both manufacturing precision and structural reliability.

The patent changes the size parameter of the root region by forming it oversized relative to the final attachment interface. This parameter change allows the use of non-cutting removal methods (such as abrasion or chemical etching) to achieve final dimensions without cutting through plies, thus resolving the contradiction between achieving tight tolerances and maintaining ply integrity.

The patent embeds the datum features and attachment fillet radii directly into the CMC root region during the manufacturing process itself, rather than requiring subsequent complex machining operations. This preliminary action transfers the precision requirements to the molding/forming stage where CMC processes can more easily achieve the required tolerances without excessive complexity.

The patent introduces an oversized root region as an intermediary form between the CMC manufacturing process and the final attachment interface. This intermediary allows the CMC process to work with larger, more tolerable dimensions while still achieving the final precise fit through non-cutting removal methods, thereby reducing processing complexity.

The patent pre-forms the outer composite plies with the correct geometry and attachment fillet radii during the CMC manufacturing process. This preliminary action ensures that the plies are never cut or damaged during subsequent machining operations, thereby preserving the full strength of the outer plies while still achieving the required attachment profile tolerances.

The patent changes the approach from cutting-based precision achievement to abrasion/etching-based precision achievement. By using parameter changes in the material removal method (from mechanical cutting to surface abrasion or chemical etching), the outer plies can be precisely shaped without compromising their structural integrity and attachment strength.