Variable geometry structure

1. A variable geometry structure comprising:

a flexural element having a distal end;

a tensioning element having a forward end and a distal end, the distal end of the tensioning element being connected to the distal end of the flexural element; and

an actuator comprising an actuator mechanism directly connected to the forward end of the tensioning element for adjusting the tensioning element to change the load placed on the flexural element, thereby bending the flexural element to change the geometry of the structure, the actuator being secured to the flexural element and the actuator mechanism being configured to adjust the tensioning element by pulling the forward end of the tensioning element, wherein

the tensioning element has at least first, second and third configurations, the flexural element being substantially planar when the tensioning element is in the first configuration, the flexural element being curved in a first direction when the tensioning element is in the second configuration, the second configuration placing a higher load on the flexural element than the first configuration, and the flexural element being curved in a second, opposite direction and being unstressed by the tensioning element in the third configuration,

the actuator being configured to move the tensioning element between the at least first, second and third configurations.

2. A variable geometry structure as claimed in claim 1 , wherein

the actuator is configured to pull the tensioning element in a longitudinal direction.

3. A variable geometry structure as claimed in claim 2 , wherein

the actuator is selected from the group consisting of a ball screw and a spool around which the tensioning element is wound.

4. A variable geometry structure as claimed in claim 1 , wherein

the tensioning element and flexural element are separated by a spacing member.

5. A variable geometry structure as claimed in claim 1 , wherein

the flexural element is elastically deformable.

6. A variable geometry structure as claimed in claim 1 , wherein

the tensioning element has a fixed length.

7. A component comprising a variable geometry structure as claimed in claim 1 .

8. A component as claimed in claim 7 , wherein

the component is selected from the group consisting of a nozzle, a radiator, a heat exchanger intake, an inlet particle separator, a vane, a combustor, a spoiler, a wing, a slat, a flap and a rudder for airframe control.

9. A variable geometry structure comprising:

a flexural element having a distal end;

a forcing element having a forward end and a distal end, the distal end of the forcing element being connected to the distal end of the flexural element; and

an actuator comprising an actuator mechanism directly connected to the forward end of the forcing element for adjusting the forcing element to change the load placed on the flexural element, thereby bending the flexural element to change the geometry of the structure, the actuator being secured to the flexural element, the actuator mechanism being configured to control the forcing element to move the flexural element between at least first, second and third fixed positions, the first fixed position being a substantially planar position, the actuator mechanism moving the flexural element in a first direction from the first fixed position to the second fixed position, and the actuator mechanism moving the flexural element in a second direction opposite from the first direction from the first fixed position to the third fixed position.

10. A variable geometry structure comprising:

a flexural element having a distal end;

a tensioning element having a forward end and a distal end, the distal end of the tensioning element being connected to the distal end of the flexural element, the tensioning element having a fixed length, the tensioning element comprising a material which returns to its original shape when a mechanical deforming load is removed, the tensioning element and the flexural element being separated by at least one spacing member, the at least one spacing member securing the tensioning element and the flexural element together; and

an actuator comprising an actuator mechanism directly connected to the forward end of the tensioning element for adjusting the tensioning element by exerting the mechanical deforming load on the tensioning element to change the load placed on the flexural element, thereby bending the flexural element to change the geometry of the structure, the actuator being secured to the flexural element.

11. A variable geometry structure comprising:

a flexural element having a distal end;

a tensioning element having a distal end, the distal end of the tensioning element being connected to the distal end of the flexural element, and the tensioning element having a proximal end, the proximal end of the tensioning element being connected to a cover member, the cover member forming an aerodynamically smooth surface with the tensioning element; and

an actuator for adjusting the tensioning element to change the load placed on the flexural element, thereby bending the flexural element to change the geometry of the structure, the actuator being configured to push or pull a portion of the tensioning element in a transverse direction, the actuator being configured to control the tensioning element to move the flexural element between at least first and second fixed positions, the first fixed position being a substantially planar position, the actuator mechanism moving the flexural element in a first direction from the first fixed position to the second fixed position.

12. A variable geometry structure as claimed in claim 11 , wherein

the portion of the tensioning element comprises a shape memory material, and the actuator is configured to heat the shape memory material above a predetermined temperature thereby changing the shape of the shape memory material and changing the load on the flexural element.

13. A variable geometry structure comprising:

a flexural element having a distal end;

a tensioning element having a distal end, the distal end of the tensioning element being connected to the distal end of the flexural element, the tensioning element comprising a cavity; and

an actuator for adjusting the tensioning element to change the load placed on the flexural element, thereby bending the flexural element to change the geometry of the structure, the tensioning element having a proximal end, the proximal end of the tensioning element being connected to a cover member, the cover member covering the flexural element, the actuator being configured to use a pressurised fluid to inflate or deflate the cavity thereby changing the shape of the cavity and changing the load on the flexural element.

14. A variable geometry structure as claimed in claim 13 , wherein

the tensioning element comprises first and second layers and wherein the cavity is formed between the first and second layers, the first and second layers being substantially planar and parallel to each other in the first fixed position.

15. A variable geometry structure comprising:

a flexural element having a distal end;

a tensioning element having a distal end, the distal end of the tensioning element being connected to the distal end of the flexural element, a cavity being formed between the tensioning element and the flexural element; and

an actuator for adjusting the tensioning element to change the load placed on the flexural element, thereby bending the flexural element to change the geometry of the structure, the tensioning element having a proximal end, the proximal end of the tensioning element being connected to a cover member, the cover member covering the flexural element, the actuator being configured to use a pressurised fluid to inflate or deflate the cavity thereby changing the shape of the cavity and changing the load on the flexural element.