Frangible airfoils

1. An airfoil defining a span extending between a root and a tip, the airfoil further defining a chord at each point along the span extending between a leading edge and a trailing edge, the airfoil comprising:

at least one frangible airfoil portion;

a residual airfoil portion adjacent to the at least one frangible airfoil portion; and one or more zones within the at least one frangible airfoil portion and within the residual airfoil portion,

wherein the at least one frangible airfoil portion and the residual airfoil portion further comprise a plurality of cavities,

wherein the plurality of cavities comprise inclusions,

and

wherein the inclusions comprise one or more materials.

2. The airfoil of claim 1 , wherein the one or more materials comprise at least one of ceramic materials, viscous-elastic materials, and metal materials.

3. The airfoil of claim 1 , the airfoil further comprising:

a core comprising a functionally graded material, the functionally graded material comprising a parent material elasticity.

4. The airfoil of claim 3 , wherein the inclusions comprise an inclusion elasticity, and wherein a ratio of the inclusion elasticity to the parent material elasticity is between 0.5 to 1.5.

5. The airfoil of claim 1 , wherein the at least one frangible airfoil portion extends along at least part of the tip, and wherein the inclusions comprise 1% volume to 10% volume of the at least one cavity of the plurality of cavities.

6. The airfoil of claim 1 , wherein the at least one frangible airfoil portion extends along an outer portion of the span, and wherein the inclusions comprise 10% volume to 20% volume of the at least one cavity of the plurality of cavities.

7. The airfoil of claim 1 , wherein the at least one frangible airfoil portion extends along at least one of the leading edge and the trailing edge, and wherein the inclusions comprise 20% volume to 99% volume of the at least one cavity of the plurality of cavities.

8. The airfoil of claim 3 , wherein the plurality of cavities comprise a shape of one or more of the following: circle, an ellipse, a rectangle, and a square.

9. An airfoil defining a span extending between a root and a tip, the airfoil further defining a chord at each point along the span extending between a leading edge and a trailing edge, the airfoil comprising:

a functionally graded material comprising a parent material elasticity; and

one or more zones comprising at least one frangible airfoil portion and a residual airfoil portion,

wherein the at least one frangible airfoil portion and the residual airfoil portion further comprise a plurality of cavities,

wherein the plurality of cavities comprise inclusions, the inclusions comprising an inclusion elasticity between 0.5 to 1.5 the parent material elasticity, and

wherein the one or more zones further comprise:

the residual airfoil portion adjacent to the at least one frangible airfoil portion at one or more fusion lines, wherein the plurality of cavities define one or more stress paths within the one or more zones, the at least one frangible airfoil portion, and the residual airfoil portion.

10. The airfoil of claim 9 , wherein the inclusions comprise one or more materials.

11. The airfoil of claim 10 , wherein the one or more materials comprise at least one of ceramic materials, viscous-elastic materials, and metal materials.

12. The airfoil of claim 11 , wherein the inclusions comprise greater than 20% volume of the at least one of the plurality of cavities.

13. The airfoil of claim 12 , wherein a ratio of the inclusion elasticity to the parent material elasticity is between 0.5 to 1.

14. The airfoil of claim 9 , wherein the inclusions comprise between 10% to 20% volume of the at least one of the plurality of cavities.

15. The airfoil of claim 14 , wherein a ratio of the inclusion elasticity to the parent material elasticity is between 0.5 to 1.2.

16. The airfoil of claim 9 , wherein the inclusions comprise less than 10% volume of the at least one of the plurality of cavities.

17. A gas turbine engine defining a central axis, the gas turbine engine comprising:

an engine shaft extending along the central axis;

a compressor attached to the engine shaft and extending radially about the central axis;

a combustor positioned downstream of the compressor to receive a compressed fluid therefrom;

a turbine mounted on the engine shaft downstream of the combustor to provide a rotational force to the compressor; and

a plurality of airfoils operably connected to the engine shaft, each of the plurality of airfoils defining a span extending between a root and a tip, each of the plurality of airfoils comprising:

a functionally graded material comprising a parent material elasticity; and

one or more zones comprising at least one frangible airfoil portion and a residual airfoil portion,

wherein the at least one frangible airfoil portion and the residual airfoil portion further comprise a plurality of cavities,

wherein of the plurality of cavities comprise inclusions, the inclusions comprising an inclusion elasticity between 0.5 to 1.5 parent material elasticity, and

wherein the one or more zones further comprise:

the residual airfoil portion adjacent to the at least one frangible airfoil portion at one or more fusion lines.

18. The gas turbine engine of claim 17 , wherein a ratio of the inclusion elasticity to the parent material elasticity is between 0.5 to 1.

19. The gas turbine engine of claim 17 , wherein a ratio of the inclusion elasticity to the parent material elasticity is between 0.5 to 1.2.

20. The gas turbine engine of claim 17 , wherein the inclusions comprise less than 10% volume of the at least one of the plurality of cavities.