Dual rotor blades having a metal leading airfoil and a trailing airfoil of a composite material for gas turbine engines

1. A rotor blade for a rotor of a gas turbine engine comprising a first airfoil component extending radially between a root and a tip and a second airfoil component, separate from the first airfoil component, extending radially between a root and a tip, the second airfoil component positioned downstream, in series, of the first airfoil component, the first airfoil component being metal and the second airfoil component being of a composite material, the first airfoil component forming the leading rotor blade component while the second airfoil component forms the trailing rotor blade component whereby the first airfoil component is suitable for transonic tip speeds while resisting foreign damage and erosion, and the composite material of the second airfoil component is a relatively lighter material, wherein an axial gap is defined between the leading airfoil component and the trailing airfoil component, and wherein the axial gap is filled with an elastomer.

2. The rotor blade as defined in claim 1 wherein the metal of the first airfoil component is selected from a group of metals containing titanium and stainless steel while the composite material of the second airfoil component is made of a light composite material such that the weight of the two-component rotor blade is less than a similar rotor blade made of solid metal.

3. The rotor blade as defined in claim 1 wherein the composite material of the second airfoil component comprises carbon nanotubes such that the weight of the two-component rotor blade is less than a similar rotor blade made of solid metal.

4. The rotor blade as defined in claim 1 wherein the composite material of the second airfoil component comprises carbon fibers placed in multiple layers and embedded with a polymer resin so that the weight of the two-component rotor blade is less than a similar rotor blade made of solid metal.

5. The rotor blade as defined in claim 1 wherein the rotor blade is a fan blade in a turbofan turbine engine.

6. The rotor blade as defined in claim 1 wherein the rotor blade is a rotor blade in any of a compressor and turbine section in a gas turbine engine.

7. A fan rotor for a turbo fan engine comprising an array of circumferentially spaced transonic dual rotor blades with each dual rotor blade having a leading blade component and a separate trailing blade component arranged in series with the leading blade component; the leading blade component made of a metal to resist foreign object damage and erosion, and the trailing blade component made of a relatively lighter material providing a light weight to the dual rotor blade such that the weight of the dual rotor blade is less than a similar rotor blade made of solid metal, wherein an axial gap is defined between the respective leading blade component and the trailing blade component, the axial gap being between 1% and 5% of the blade pitch, and wherein each of the axial gaps is filled with an elastomer.

8. The fan rotor as defined in claim 7 wherein leading rotor blade component is made of a strong metal selected from a group containing titanium or stainless steel.

9. The fan rotor as defined in claim 8 wherein the trailing blade component is made of composite material including carbon nanotubes such that the weight of the dual rotor blade is less than a similar rotor blade made of solid metal.

10. The fan rotor as defined in claim 8 wherein the trailing blade component is made of a composite material comprising carbon fibers placed in multiple layers and embedded with a polymer resin such as an epoxy-based resin so that the weight of the dual rotor blade is less than a similar rotor blade made of solid metal.