Vane arc segment platform flange with cap

1. A vane arc segment comprising:

an airfoil piece including a first platform, a second platform, and an airfoil section between the first platform and the second platform, at least the first platform being formed of a fiber-reinforced composite (FRC) and defining a radial flange, the radial flange defining opposed circumferential flange sides and a radial face joining the opposed circumferential flange sides, the radial face having a curved profile; and

a cap fitted on the radial flange.

2. The vane arc segment as recited in claim 1 , wherein the cap is formed of a superalloy.

3. The vane arc segment as recited in claim 1 , wherein the cap is friction-fit on the radial flange.

4. The vane arc segment as recited in claim 1 , wherein the cap includes an acute corner.

5. The vane arc segment as recited in claim 1 , wherein the cap includes first and second radial walls and a tangential wall joining the first and second radial walls.

6. The vane arc segment as recited in claim 5 , wherein the cap mechanically constrains the radial flange.

7. The vane arc segment as recited in claim 1 , wherein the FRC is a ceramic matrix composite.

8. A vane ring assembly comprising:

an airfoil piece including a first platform, a second platform, and an airfoil section between the first platform and the second platform, the first platform defining a radial flange, the first platform being formed of a ceramic matrix composite;

a mating component adjacent the radial flange; and

an anti-wear element in an interface between the radial flange and the mating component the anti-wear element including first and second radial walls that provide circumferential sides of the anti-wear element, a tangential wall joining the first and second radial walls, and an aft wall joining the first and second radial walls and the tangential wall.

9. The assembly as recited in claim 8 , wherein the anti-wear element is formed of a superalloy.

10. The assembly as recited in claim 8 , wherein the interface is a radial interface.

11. The assembly as recited in claim 8 , wherein the anti-wear element is friction-fit on the radial flange.

12. A gas turbine engine comprising:

first and second support structures; and

vane arc segments supported between the first and second support structures, each said vane arc segment including

an airfoil piece having a first platform, a second platform, and an airfoil section between the first platform and the second platform, at least the first platform being formed of a fiber-reinforced composite (FRC) and defining a radial flange, the radial flange defining opposed circumferential flange sides and a radial face joining the opposed circumferential flange sides, the radial face having a curved profile, and

a cap fitted on the radial flange.

13. The engine as recited in claim 12 , wherein the cap is non-destructively removable from the radial flange.

14. The engine as recited in claim 13 , wherein the cap is formed of a superalloy and is friction-fit on the radial flange.

15. The engine as recited in claim 14 , wherein the FRC is a laminate that includes radially oriented fiber plies and the cap mechanically constrains the radial flange.

16. The vane arc segment as recited in claim 1 , wherein the curved profile is a cylindrical surface segment.

17. The vane arc segment as recited in claim 1 , wherein the FRC is a laminate of fiber plies, and the fiber plies in the radial flange are radially oriented at a radial face of the radial flange.

18. The vane arc segment as recited in claim 1 , wherein the first platform has first and second circumferential mate faces, forward and aft faces, an inner side from which the airfoil section extends, and an outer side opposite the inner side, and the radial flange is on the outer side and extends along at least 50% of an extent of the first circumferential mate face in a direction between the forward and aft faces.

19. The assembly as recited in claim 8 , wherein the aft wall, the first and second radial walls, and the tangential wall define an inside acute corner.

20. The assembly as recited in claim 8 , wherein the radial flange defines opposed circumferential flange sides and a radial face joining the opposed circumferential flange sides, and the radial face has a curved profile of a cylindrical surface segment.