Platform apparatus for propulsion rotor

1. A platform for use between adjacent propulsion rotor airfoils joined to a rotor disk to provide an inner flowpath boundary, the platform comprising:

an axially extending I-beam supporting a radially outer skin having a flowpath surface,

wherein the I-beam includes an inner I-flange disposed at an inner edge of an axially extending I-web, and an outer I-flange disposed at an outer edge of the I-web,

wherein the I-beam includes a forward end flange extending laterally outward from a forward end of the I-web at a location that is radially distanced from a forward end of the inner I-flange and the outer I-flange and an aft end flange extending laterally outward from an aft end of the I-web at a location that is radially distanced from the inner I-flange and an aft end of the outer I-flange,

wherein the radially outer skin is disposed on top of and joined to the outer I-flange,

wherein the radially outer skin includes a forward end wall extending forward of the forward end flange and an aft end wall extending aft of the aft end flange, and

wherein the forward end flange axially abuts the forward end wall of the radially outer skin, and the aft end flange axially abuts the aft end wall of the radially outer skin.

2. The platform of claim 1 , wherein the I-beam is a monolithic whole including the I-web, the inner and outer I-flanges, and the forward and aft end flanges.

3. The platform of claim 1 , wherein the I-beam is made from a thermoplastic material.

4. The platform of claim 1 , wherein the I-beam is made from a nonmetallic composite material.

5. The platform of claim 4 , wherein the I-beam includes reinforcing material extending from the I-web into the forward and aft end flanges.

6. The platform of claim 1 , wherein the I-beam includes back-to-back first and second C-beams joined to each other.

7. The platform of claim 6 , wherein:

the first C-beam includes an axially extending first C-web disposed between first inner and outer C-flanges, and includes first forward and aft end tabs at axial ends thereof;

the second C-beam includes an axially extending second C-web disposed between inner and outer second C-flanges, and includes second forward and aft end tabs at axial ends thereof;

the first and second C-beams open in opposite first and second side directions; and

the first and second C-webs are disposed back-to-back along a planar interface.

8. The platform of claim 7 , further comprising each of the first and second C-beams being a monolithic whole including the respective C-web, C-flanges, and end tabs.

9. The platform of claim 7 , wherein each of the C-beams includes reinforcing material extending from the respective C-web into the respective forward and aft end tabs.

10. The platform of claim 6 , wherein each of the C-beams is made from a thermoplastic material.

11. The platform of claim 6 , wherein each of the C-beams is made from a nonmetallic composite material.

12. The platform of claim 1 , wherein the I-beam is asymmetrical about a center plane of the I-web.

13. The platform of claim 1 , further comprising weight relief holes disposed in the I-web.

14. A propulsion rotor assembly, comprising:

a plurality of circumferentially spaced apart rotor blades extending radially outwardly from a rotor disk,

a platform between each adjacent pair of the blades and joined to the rotor disk, each platform including:

an axially extending I-beam supporting a radially outer skin having a flowpath surface,

wherein the I-beam includes an inner I-flange disposed at an inner edge of an axially extending I-web, and an outer I-flange disposed at an outer edge of the I-web,

wherein the I-beam includes a forward end flange extending laterally outward from a forward end of the I-web at a location that is radially distanced from a forward end of the inner I-flange and the outer I-flange, and an aft end flange extending laterally outward from an aft end of the I-web at a location that is radially distanced from the inner I-flange and an aft end of the outer I-flange,

wherein the radially outer skin is disposed on top of and joined to the outer I-flange,

wherein the radially outer skin includes a forward end wall extending forward of the forward end flange and an aft end wall extending aft of the aft end flange, and

wherein the forward end flange axially abuts the forward end wall of the radially outer skin and the aft end flange axially abuts the aft end wall of the radially outer skin.

15. The assembly of claim 14 , wherein:

the I-beam includes back-to-back first and second C-beams;

the first C-beam includes an axially extending first C-web disposed between first inner and outer C-flanges, and includes first forward and aft end tabs at axial ends thereof;

the second C-beam includes an axially extending second C-web disposed between inner and outer second C-flanges, and includes second forward and aft end tabs at axial ends thereof;

the first and second C-beams open in opposite first and second side directions; and

the first and second C-webs webs are disposed back-to-back and joined together along a planar interface.

16. The assembly of claim 15 , further comprising each of the first and second C-beams being a monolithic whole including the respective C-web, C-flanges, and end tabs.

17. The assembly of claim 16 , wherein each of the first and second C-beams is made from a nonmetallic composite material.

18. The assembly of claim 17 , wherein each of the first and second C-beams includes reinforcing material extending from the respective C-web into the respective forward and aft end tabs.