Airfoil with serpentine fiber ply layup

1. An airfoil comprising:

an airfoil section formed of a fiber-reinforced composite comprised of fiber plies, the fiber plies including

at least one overwrap fiber ply that defines first and second sides and leading and trailing ends of the airfoil section, the at least one overwrap fiber ply circumscribing an internal cavity,

first and second support fiber plies defining respective first and second radial tubes in the internal cavity, and

a serpentine fiber ply that winds i) from the first side and around the first radial tube to the second side, ii) then from the second side back to the first side, and iii) then from the first side and around the second radial tube back to the second side.

2. The airfoil as recited in claim 1 , wherein the serpentine fiber ply is in contact with the first and second sides of the at least one overwrap ply.

3. The airfoil as recited in claim 1 , wherein the serpentine fiber ply is in contact with the first side at first and second chord-length locations that are separated by a first non-contact region where the serpentine fiber ply does not contact the first side.

4. The airfoil as recited in claim 3 , wherein the serpentine fiber ply is in contact with the second side at third and fourth chord-length locations that are separated by a second non-contact region where the serpentine fiber ply does not contact the second side.

5. The airfoil as recited in claim 4 , wherein the serpentine fiber ply is in contact with the first and second radial tubes.

6. The airfoil as recited in claim 1 , wherein the serpentine fiber ply includes a first section that is in contact with the first and second sides of the at least one overwrap fiber ply and is in contact with the first radial tube, and the first section wraps at least 360 degrees around the first radial tube.

7. The airfoil as recited in claim 6 , wherein the serpentine fiber ply includes a second section that is in contact with the first and second sides of the at least one overwrap fiber ply, and the second section is in contact with the second radial tube.

8. The airfoil as recited in claim 1 , wherein the serpentine fiber ply includes a first section that is in contact with the first and second sides of the at least one overwrap fiber ply, and the first section wraps around the first radial tube and overlaps itself.

9. A gas turbine engine comprising:

a compressor section;

a combustor in fluid communication with the compressor section; and

a turbine section in fluid communication with the combustor, at least one of the turbine section or the compressor section having airfoils disposed about a central axis of the gas turbine engine, each of the airfoils includes:

an airfoil section formed of a fiber-reinforced composite comprised of fiber plies, the fiber plies including

at least one overwrap fiber ply that defines first and second sides and leading and trailing ends of the airfoil section, the at least one overwrap fiber ply circumscribing an internal cavity,

first and second support fiber plies defining respective first and second radial tubes in the internal cavity, and

a serpentine fiber ply that winds i) from the first side and around the first radial tube to the second side, ii) then from the second side back to the first side, and iii) then from the first side and around the second radial tube back to the second side.

10. The gas turbine engine as recited in claim 9 , wherein the serpentine fiber ply is in contact with the first and second sides of the at least one overwrap ply.

11. The gas turbine engine as recited in claim 9 , wherein the serpentine fiber ply is in contact with the first side at first and second chord-length locations that are separated by a first non-contact region where the serpentine fiber ply does not contact the first side, and the serpentine fiber ply is in contact with the second side at third and fourth chord-length locations that are separated by a second non-contact region where the serpentine fiber ply does not contact the second side.

12. The gas turbine engine as recited in claim 11 , wherein the serpentine fiber ply is in contact with the first and second radial tubes.

13. The gas turbine engine as recited in claim 9 , wherein the serpentine fiber ply includes a first section that is in contact with the first and second sides of the at least one overwrap fiber ply and is in contact with the first radial tube, and the first section wraps at least 360 degrees around the first radial tube.

14. The gas turbine engine as recited in claim 13 , wherein the serpentine fiber ply includes a second section that is in contact with the first and second sides of the at least one overwrap fiber ply, and the second section is in contact with the second radial tube.

15. The gas turbine engine as recited in claim 9 , wherein the serpentine fiber ply includes a first section that is in contact with the first and second sides of the at least one overwrap fiber ply, and the first section wraps around the first radial tube and overlaps itself.

16. A method for fabricating an airfoil, the method comprising:

forming an airfoil section of the airfoil from a fiber-reinforced composite comprised of fiber plies that include first and second support fiber plies, a serpentine fiber ply, and at least one overlap fiber play by

arranging the first and second support fiber plies around prongs of a forked mandrel to form respective first and second radial tubes,

arranging the serpentine fiber ply to wind around the first and second radial tubes,

arranging the at least one overwrap fiber ply around the first and second support fiber plies and the serpentine fiber ply to define first and second sides of the airfoil section, leading and trailing ends of the airfoil section, and an internal cavity in the airfoil section, such that the serpentine fiber ply winds i) from the first side and around the first radial tube to the second side, ii) then from the second side back to the first side, and iii) then from the first side and around the second radial tube back to the second side.

17. The method as recited in claim 16 , wherein the serpentine fiber ply is in contact with the first and second sides of the at least one overwrap ply.

18. The method as recited in claim 16 , wherein the serpentine fiber ply is in contact with the first side at first and second chord-length locations that are separated by a first non-contact region where the serpentine fiber ply does not contact the first side, and the serpentine fiber ply is in contact with the second side at third and fourth chord-length locations that are separated by a second non-contact region where the serpentine fiber ply does not contact the second side.

19. The method as recited in claim 16 , wherein the serpentine fiber ply includes a first section that is in contact with the first and second sides of the at least one overwrap fiber ply and is in contact with the first radial tube, and the first section wraps at least 360 degrees around the first radial tube.

20. The method as recited in claim 16 , wherein the serpentine fiber ply includes a first section that is in contact with the first and second sides of the at least one overwrap fiber ply, and the first section wraps around the first radial tube and overlaps itself.