Composite rotor blade manufacturing method and apparatus
Apparatus and methods are disclosed for manufacture of a composite structure, such as a composite rotor blade spar or composite rotor blade. A first mold may define a first mold surface and a second mold may include a rigid layer and a heated layer secured to the rigid layer and defining a second mold surface. A plurality of heating elements embedded in the second mold may be activated according to different temperature progressions to cure portions of the uncured composite rotor blade positioned coextensive therewith. In some embodiments, the second mold defines a root portion and first and second branch portions. A shear web placed between the branch portions may be bonded to a blade skin positioned within the mold. The rotor blade may include a rotor blade spar having leading and trailing edge fairings secured thereto or the blade spar may define a complete airfoil contour.
1. A method for manufacturing a rotor blade comprising:
providing a first mold defining a first mold surface;
providing a second mold comprising a rigid core and a heated layer secured thereto, the heated layer defining a second mold surface;
providing a plurality of pressure sensors embedded in the heated layer;
the second mold further comprising at least one heating elements embedded therein;
placing an uncured composite rotor blade between first and second molds, such that the uncured composite rotor blade is positioned between the first and second mold surfaces, the uncured composite rotor blade having non-uniform thickness, the first and second mold surfaces being contoured corresponding to an outer surface of the uncured composite rotor blade;
activating a plurality of heating elements effective to cure the uncured composite rotor blade; and
controlling activation of the plurality of heating elements according to outputs of the plurality of pressure sensors detecting different pressures corresponding to desired pressures for a plurality of zones of the uncured composite rotor blade in accordance with cure dynamics of the non-uniform wall thickness within the plurality of zones.
2. The method of claim 1 , wherein the heated layer further comprises a thermally expandable material having an anisotropic layer thickness across the plurality of heating elements effective to provide a desired anisotropic pressure in accordance with cure dynamics of the non-uniform wall thickness of the uncured composite blade when the plurality of heating elements are activated according to the plurality of different temperature progressions.
3. The method of claim 2 , wherein activating the plurality of heating elements comprises simultaneously activating the plurality of heating elements according to a plurality of different temperature progressions effective to cure portions of the uncured composite rotor blade coextensive with each heating element of the plurality of heating elements.
4. The method of claim 1 , wherein the heated layer includes a thermally expandable material having a coefficient of thermal expansion effective to cause volumetric expansion of the heated layer of at least 10 percent during activating of the plurality of heating elements.
5. The method of claim 1 , wherein the heated layer includes a thermally expandable material having a coefficient of thermal expansion effective to cause volumetric expansion of the heated layer of at least 20 percent during activating of the plurality of heating elements.
6. The method of claim 1 , wherein the uncured composite rotor blade is hollow such that one of the first mold surface and the second mold surface defines a contour of an outer surface of the uncured composite rotor blade and the other of the first mold surface and second mold surface defines a contour of the inner surface of the uncured composite rotor blade.
7. The method of claim 6 , wherein the second mold surface defines the contour of the inner surface of the uncured composite rotor blade.
8. The method of claim 6 , wherein the uncured composite rotor blade has a proximal end and a distal end and has a non-uniform wall thickness that decreases with distance from the proximal end along a substantial portion of the uncured composite rotor blade.
9. The method of claim 6 , wherein:
the uncured composite rotor blade comprises a plurality of ply allocations; and
placing the uncured composite rotor blade between the first and second molds comprises, for each ply allocation placing the ply allocation between the first and second mold surfaces; and
debulking the ply allocation.
10. The method of claim 9 , wherein debulking the ply allocation comprises applying at least one of heat and pressure.
11. The method of claim 10 , wherein debulking the ply allocation further comprises:
placing a shim over the ply allocations; and
placing one or more of the first and second molds such that the ply allocation and shim are captured between the first and second mold surfaces.
12. The method of claim 1 , wherein the second mold includes a first mold section and a second mold section, the first and second mold section being separable from one another and each including a portion of a one or more of the rigid layer and the heated layer, the method further comprising:
placing a composite structure between the first mold section and the second mold section, the composite structure contacting the uncured composite rotor blade.
13. The method of claim 12 , further comprising placing the composite structure having the composite structure contacting opposing portions of an inner concave surface of the uncured composite rotor blade.
14. The method of claim 13 , wherein:
the composite structure comprises a cured composite structure;
a chord of the uncured composite rotor blade defines a helical contour along the longitudinal axis thereof; and
the composite structure has a helical shape corresponding to the helical contour of the chord of the uncured composite rotor blade.