Composite airfoil for gas turbine

1. An airfoil for a gas turbine engine comprising:

an airfoil section extending between a leading edge and a trailing edge in a chordwise direction and extending between a tip and a root section in a spanwise direction, the airfoil section defining a suction side and a pressure side separated in a thickness direction;

wherein a composite core defines the root section and a portion of the airfoil section such that the composite core is spaced apart from the tip, and the composite core includes a three-dimensional network of woven fibers;

wherein first and second skins extend along opposed sides of the composite core for at least some span positions of the airfoil section and join together to define the tip, and each of the first and second skins is a composite skin including a two-dimensional network of woven fibers; and

wherein the airfoil section is free of the core for at least a majority of span positions of the airfoil section.

2. The airfoil as recited in claim 1 , wherein the three-dimensional network of woven fibers is formed from a dry fiber preform.

3. The airfoil as recited in claim 2 , wherein the composite core and the first and second skins are formed together by resin transfer molding or by resin pressure molding to define the airfoil section and the root section.

4. The airfoil as recited in claim 3 , wherein the two-dimensional network of fibers is formed from a pre-impregnated fabric or a pre-impregnated tape.

5. The airfoil as recited in claim 4 , wherein the composite core terminates in the spanwise direction along the airfoil section prior to about 25% span.

6. The airfoil as recited in claim 5 , wherein the core is skewed toward the leading edge.

7. The airfoil as recited in claim 6 , wherein a center of mass of the composite core is between the leading edge and a reference plane, and the reference plane is defined as a plane equidistant between the leading edge and the trailing edge for each span position of the airfoil section.

8. The airfoil as recited in claim 7 , wherein the center of mass is along a mean camber line bisecting the airfoil section in the thickness direction.

9. The airfoil as recited in claim 1 , wherein the first and second skins are joined at both the leading edge and the trailing edge.

10. The airfoil as recited in claim 9 , wherein the composite core extends between the leading edge and trailing edge at a first span position inward of a second span position relative to the spanwise direction, and wherein the first and second skins are joined together at the leading edge and the trailing edge at the second span position.

11. A gas turbine engine comprising:

a fan section including a fan hub that carries a plurality of fan blades, the fan hub rotatable about an engine longitudinal axis;

a compressor section;

a turbine section that drives the compressor section and the fan section; and

wherein each of the plurality of fan blades comprises:

a root section received in a respective slot defined by the fan hub; and

an airfoil section extending between a leading edge and a trailing edge in a chordwise direction and extending between a tip and the root section in a spanwise direction, the airfoil section defining a suction side and a pressure side separated in a thickness direction;

wherein a composite core defines the root section and a portion of the airfoil section such that the composite core is spaced apart from the tip;

wherein first and second skins extend along opposed sides of the composite core for at least some span positions of the airfoil section and join together to define the tip, and each of the first and second skins is a composite skin including a two-dimensional network of woven fibers; and

wherein the airfoil section is free of the core for at least a majority of span positions of the airfoil section.

12. The gas turbine engine as recited in claim 11 , wherein the composite core includes a three-dimensional network of woven fibers formed from a dry fiber preform, the two-dimensional network of fibers is formed from a pre-impregnated fabric or a pre-impregnated tape, and the composite core and the first and second skins are formed together by resin pressure molding or by resin transfer molding to define the airfoil section and the root section.

13. The gas turbine engine as recited in claim 12 , wherein the core terminates in the spanwise direction along the airfoil section prior to about 25% span.

14. The gas turbine engine as recited in claim 13 , wherein the root section defines a dovetail geometry that interfaces with the respective slot, and the first and second skins extend along the dovetail geometry to space apart the core from walls of the respective slot.

15. The gas turbine engine as recited in claim 11 , wherein a center of mass of the composite core is between the leading edge and a reference plane, and the reference plane is defined as a plane equidistant between the leading edge and the trailing edge for each span position of the airfoil section.

16. The airfoil as recited in claim 15 , wherein the composite core and the first and second composite skins include a network of woven fibers.

17. The airfoil as recited in claim 15 , wherein the center of mass is along a mean camber line bisecting the airfoil section in the thickness direction.

18. The airfoil as recited in claim 15 , wherein the first and second skins are joined at both the leading edge and the trailing edge.

19. The airfoil as recited in claim 18 , wherein the composite core extends between the leading edge and trailing edge at a first span position inward of a second span position relative to the spanwise direction, and wherein the first and second skins are joined together at the leading edge and the trailing edge at the second span position.

20. An airfoil for a gas turbine engine comprising:

an airfoil section extending between a leading edge and a trailing edge in a chordwise direction and extending between a tip and a root section in a spanwise direction, the airfoil section defining a suction side and a pressure side separated in a thickness direction;

wherein a composite core defines the root section and a portion of the airfoil section such that the composite core is spaced apart from the tip;

wherein first and second composite skins extend along opposed sides of the composite core for at least some span positions of the airfoil section and join together to define the tip; and

wherein the composite core terminates in the spanwise direction along the airfoil section prior to about 25% span and includes a center of mass between the leading edge and a reference plane, and the reference plane is defined as a plane equidistant between the leading edge and the trailing edge for each span position of the airfoil section.