Composite gas turbine engine component

1. A platform for a gas turbine engine comprising:

a platform body including a gas path surface extending axially between a leading edge and a trailing edge and extending circumferentially between opposed mate faces;

a plurality of platform flanges extending from the platform body to define one or more slots, the one or more slots dimensioned to receive a respective flange of a rotatable hub, and each platform flange includes a retention member dimensioned to receive a retention pin to mount the platform body;

wherein a composite wrap extends about a perimeter of the platform body to define an internal cavity and the plurality of platform flanges; and

at least one honeycomb core including a plurality of cells that is disposed in the internal cavity.

2. The platform as recited in claim 1 , wherein the composite wrap includes a plurality of composite layers that join together to define the internal cavity.

3. The platform as recited in claim 2 , wherein the composite wrap extends about a perimeter of the at least one honeycomb core.

4. The platform as recited in claim 3 , wherein the retention member is co-molded with the plurality of composite layers and the at least one honeycomb core.

5. The platform as recited in claim 3 , wherein the perimeter of the at least one honeycomb core is dimensioned such that circumferential walls of the at least one honeycomb core taper radially inwardly towards the plurality of platform flanges.

6. The platform as recited in claim 3 , wherein the retention member is a bushing between the composite wrap and the perimeter of the at least one honeycomb core.

7. The platform as recited in claim 6 , wherein the composite wrap includes one or more composite layers that loop about the at least one honeycomb core and the bushing to define a respective one of the platform flanges.

8. The platform as recited in claim 1 , wherein the at least one honeycomb core is dimensioned to span between at least two of the platform flanges.

9. The platform as recited in claim 8 , wherein the at least one honeycomb core is dimensioned to span across each of the platform flanges.

10. The platform as recited in claim 1 , wherein the at least one honeycomb core includes first, second and third platform cores, and the platform body includes a plurality of internal ribs that divide the internal cavity into first, second and third compartments that receive respective ones of the first, second and third platform cores.

11. The platform as recited in claim 10 , wherein:

each of the first and third platform cores is axially aligned with at least one of platform flanges, and the second platform core is spaced apart axially from the platform flanges; and

the first, second and third platform cores include first, second and third constructions, respectively, and the second construction differs in density from at least one of the first and third constructions.

12. A rotor assembly for a gas turbine engine comprising:

a rotatable hub extending along a longitudinal axis and carrying an array of airfoils; and

an array of platforms, each one of the platforms defining a gas path surface between adjacent airfoils of the array of airfoils, and wherein each of the platforms comprises:

first, second and third platform cores;

a composite wrap defining a platform body and a plurality of platform flanges that mount the platform to the hub, and the composite wrap extending about a perimeter of the first, second and third platform cores; and

a plurality of internal ribs that divide the internal cavity into first, second and third compartments that receive respective ones of the first, second and third platform cores such that the first and third platform cores are axially aligned with the plurality of flanges and such that the second platform core is spaced apart axially from the plurality of flanges with respect to the longitudinal axis.

13. The rotor assembly as recited in claim 12 , wherein the second platform core is between the first and second platform cores.

14. The rotor assembly as recited in claim 12 , wherein the first and third platform cores define the plurality of platform flanges.

15. The rotor assembly as recited in claim 12 , wherein the first, second and third platform cores include first, second and third constructions, respectively, and the second construction differs in stiffness from each of the first and third constructions.

16. The rotor assembly as recited in claim 15 , wherein at least one of the first, second and third platform cores is a honeycomb core including a plurality of cells.

17. The rotor assembly as recited in claim 12 , wherein each platform flange includes a retention member dimensioned to receive a retention pin to mount the platform body to the hub.

18. A gas turbine engine comprising:

a fan section;

a compressor section;

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

a rotor assembly comprising:

a hub rotatable about an engine longitudinal axis, the hub including a plurality of flanges;

an array of airfoils circumferentially distributed about an outer periphery of the hub, each one of the airfoils including an airfoil section extending from a root section mounted to the hub;

an array of platforms circumferentially distributed about the outer periphery of the hub to define an inner gas path boundary between adjacent airfoils of the array of airfoils, and each of the platforms comprising:

at least one honeycomb core including a plurality of cells; and

a composite wrap extending about the at least one honeycomb core to define a plurality of platform flanges; and

a plurality of retention pins, each one of the retention pins extending through the flanges of the hub and through the platform flanges of a respective one of the platforms to mechanically attach the respective one of the platforms to the hub.

19. The gas turbine engine as recited in claim 18 , wherein the fan section comprises the rotor assembly.

20. The gas turbine engine as recited in claim 18 , wherein:

the at least one honeycomb core includes first, second and third platform cores; and

each platform includes a plurality of internal ribs between respective ones of the first, second and third platform cores such that the first and third platform cores are axially aligned with the platform flanges and such that the second core is spaced apart axially from the platform flanges with respect to the engine longitudinal axis.

21. The rotor assembly as recited in claim 13 , wherein:

each platform flange includes a retention member dimensioned to receive a retention pin to mount the platform body to the hub; and

the plurality of internal ribs extend circumferentially between opposed sidewalls bounding the internal cavity such that the second platform core is axially spaced apart from the first and second platform cores.

22. The gas turbine engine as recited in claim 20 , wherein:

the retention members of the respective platform are axially aligned along a pin axis and are dimensioned to slideably receive a common one of the retention pins to mount the respective platform to the hub;

the retention member is a bushing between the composite wrap and the perimeter of the at least one honeycomb core; and

the composite wrap includes one or more composite layers that loop about the first, second and third platform cores and each of the bushings to define the platform flanges.