Casing with tunable lattice structure

1. A casing defining a radial direction, an axial direction, and a circumferential direction, the casing comprising:

an annular inner wall extending along the axial direction;

an annular outer wall extending along the axial direction, the outer wall spaced apart from the inner wall along the radial direction; and

an auxetic structure extending from the inner wall to the outer wall, the auxetic structure including a plurality of lattice elements, each lattice element extending along the circumferential direction and from the inner wall to the outer wall along the radial direction, the plurality of lattice elements spaced apart from one another along the axial direction,

wherein at least one aperture is defined in the auxetic structure for a flow of fluid from one portion of the auxetic structure to another portion of the auxetic structure,

wherein the inner wall, outer wall, and auxetic structure are integrally formed as a single monolithic component,

wherein the inner wall is discontinuous along the axial direction such that the inner wall comprises a plurality of inner wall segments, and

wherein an opening is defined between adjacent inner wall segments.

2. The casing of claim 1 , wherein the auxetic structure adjacent a first inner wall segment of the plurality of inner wall segments is structurally different from the auxetic structure adjacent a second inner wall segment of the plurality of inner wall segments.

3. The casing of claim 2 , wherein the auxetic structure comprises a plurality of lattice members, each lattice member extending at an angle with respect to the axial direction, and wherein the angle of the lattice members adjacent the first inner wall segment is different from the angle of the lattice members adjacent the second inner wall segment.

4. The casing of claim 1 , wherein the outer wall is discontinuous along the axial direction such that the outer wall comprises a plurality of outer wall segments, and wherein an opening is defined between adjacent outer wall segments.

5. The casing of claim 4 , wherein the auxetic structure adjacent a first outer wall segment of the plurality of outer wall segments is structurally different from the auxetic structure adjacent a second outer wall segment of the plurality of outer wall segments.

6. The casing of claim 5 , wherein the auxetic structure comprises a plurality of lattice members, each lattice member extending at an angle with respect to the axial direction, and wherein the angle of the lattice members adjacent the first outer wall segment is different from the angle of the lattice members adjacent the second outer wall segment.

7. The casing of claim 1 , wherein the auxetic structure defines an inner flow path defined adjacent the inner wall and an outer flow path defined adjacent the outer wall, and wherein the inner flow path is separated from the outer flow path by a divider member extending along the axial direction.

8. An additively manufactured casing defining a radial direction, an axial direction, and a circumferential direction, the additively manufactured casing comprising:

an annular inner wall extending along the axial direction;

an annular outer wall extending along the axial direction, the outer wall spaced apart from the inner wall along the radial direction; and

an auxetic structure extending from the inner wall to the outer wall, the auxetic structure including a plurality of lattice elements, each lattice element extending along the circumferential direction and from the inner wall to the outer wall along the radial direction, the plurality of lattice elements spaced apart from one another along the axial direction,

wherein the auxetic structure is configured to vary the thermal characteristics of the casing along the axial direction,

wherein the outer wall is discontinuous along the axial direction such that the outer wall comprises a plurality of outer wall segments, wherein an opening is defined between adjacent outer wall segments,

wherein the auxetic structure varies between at least two adjacent outer wall segments, and

wherein the auxetic structure comprises a first auxetic section and a second auxetic section, the first auxetic section differing structurally from the second auxetic section.

9. The additively manufactured casing of claim 8 , wherein the inner wall is discontinuous along the axial direction such that the inner wall comprises a plurality of inner wall segments, wherein an opening is defined between adjacent inner wall segments, and wherein the auxetic structure varies between at least two adjacent inner wall segments.

10. The additively manufactured casing of claim 8 , wherein the casing is a housing of a gas turbine engine, and wherein the first auxetic section is defined adjacent a first module of the gas turbine engine and the second auxetic section is defined adjacent a second module of the gas turbine engine, the second module axially spaced from the first module.

11. The additively manufactured casing of claim 8 , wherein the casing is a housing of a gas turbine engine, and wherein the first auxetic section is defined adjacent a first stage of a turbine section of the gas turbine engine and the second auxetic section is defined adjacent a second stage of the turbine section, the second stage downstream of the first stage.

12. The additively manufactured casing of claim 8 , wherein each lattice element comprises a plurality of lattice members, each lattice member extending at an angle with respect to the axial direction, and wherein the angle of the lattice members in the first auxetic section is different from the angle of the lattice members in the second auxetic section.

13. The additively manufactured casing of claim 8 , wherein the outer wall includes an outer wall flange that extends outward along the radial direction from the outer wall and is integral with the outer wall.

14. The additively manufactured casing of claim 13 , wherein a flange opening is defined in the outer wall flange.

15. The additively manufactured casing of claim 14 , wherein the flange opening receives a fastener to assemble the additively manufactured casing with a mating structure.

16. A method of manufacturing a casing, the method comprising:

depositing a layer of additive material on a bed of an additive manufacturing machine; and

selectively directing energy from an energy source onto the layer of additive material to fuse a portion of the additive material and form the casing, the casing defining a radial direction, an axial direction, and a circumferential direction, the casing comprising:

an annular inner wall extending along the axial direction;

an annular outer wall extending along the axial direction, the outer wall spaced apart from the inner wall along the radial direction; and

an auxetic structure extending from the inner wall to the outer wall, the auxetic structure including a plurality of lattice elements, each lattice element extending along the circumferential direction and from the inner wall to the outer wall along the radial direction, the plurality of lattice elements spaced apart from one another along the axial direction,

wherein at least one aperture is defined in at least one lattice element,

wherein the outer wall is discontinuous along the axial direction such that the outer wall comprises a plurality of outer wall segments, and

wherein an opening is defined between adjacent outer wall segments.

17. The method of claim 16 , wherein the inner wall, outer wall, and auxetic structure are integrally formed as a single monolithic component.

18. The method of claim 16 , wherein the auxetic structure adjacent a first outer wall segment of the plurality of outer wall segments is structurally different from the auxetic structure adjacent a second outer wall segment of the plurality of outer wall segments.

19. The method of claim 18 , wherein the auxetic structure comprises a plurality of lattice members, each lattice member extending at an angle with respect to the axial direction, and wherein the angle of the lattice members adjacent the first outer wall segment is different from the angle of the lattice members adjacent the second outer wall segment.