Expandable bladders as tooling for composite parts

1. A method for fabricating a composite part, the method comprising:

laying up a preform that is made of fiber reinforced material and that includes a cavity;

inserting one or more bladders that are loaded with expandable pellets into the cavity;

inserting filler pellets into the cavity that are external to the one or more bladders;

inflating the one or more bladders in response to a triggering condition that increases volumes of the expandable pellets and causes the pellets to force flexible casings of the one or more bladders outward;

consolidating the preform while the one or more bladders are inflated;

deflating the one or more bladders by cooling the one or more bladders; and

removing the one or more bladders from the cavity.

2. The method of claim 1 further comprising:

hardening the preform into a composite part while the one or more bladders are inflated.

3. The method of claim 1 further comprising:

increasing volumes of the expandable pellets is performed via a foaming agent within the pellets, wherein:

inflation of the one or more bladders is caused by the volumes of the pellets increasing, and wherein:

deflating the one or more bladders comprises cooling the expandable pellets below a foaming temperature of the foaming agent.

4. The method of claim 1 wherein:

the filler pellets comprise additional expandable pellets.

5. The method of claim 1 further comprising:

inserting an additional bladder that is loaded with additional expandable pellets into the cavity.

6. The method of claim 1 further comprising:

arranging the one or more bladders within the cavity based on a cross-sectional shape of the cavity.

7. The method of claim 1 further comprising:

selecting shapes of the one or more bladders based on a cross-sectional shape of the cavity.

8. The method of claim 1 further comprising:

laying the preform up against a mandrel prior to inflating the one or more bladders.

9. The method of claim 1 wherein:

increasing the volumes of the pellets via releasing gas by triggering a foaming agent.

10. The method of claim 1 wherein:

the triggering condition is selected from the group consisting of: temperature triggered reactions, depressurization, ultraviolet triggered chemical reactions, and mixing of additional parts.

11. The method of claim 1 further comprising:

hardening the preform to form a portion of an aircraft.

12. The method of claim 1 wherein:

laying up the preform that is made of fiber reinforced material comprises laying up a preform that is made of Carbon Fiber Reinforced Polymer (CFRP).

13. The method of claim 1 wherein:

inserting the one or more bladders that are loaded with expandable pellets comprises inserting one or more bladders that are loaded with pellets that each comprise a matrix of flexible material having airtight pockets.

14. The method of claim 1 wherein:

inflating the one or more bladders comprises activating a foaming agent.

15. The method of claim 14 wherein:

activating the foaming agent causes the expandable pellets increase in size.

16. The method of claim 1 wherein:

inflating the one or more bladders applies forces to an elastically deformable material of the flexible casings of the one or more bladders.

17. The method of claim 1 wherein:

deflating the one or more bladders comprises piercing the one or more bladders.

18. The method of claim 1 wherein:

deflating the one or more bladders comprises operating a port at the one or more bladders.

19. The method of claim 1 further comprising:

including one or more bars of rigid material within the one or more bladders.

20. The method of claim 19 wherein:

including the one or more bars of rigid material comprises inserting one or more bars that are hollow.

21. A non-transitory computer readable medium embodying programmed instructions which, when executed by a processor, are operable for performing a method for fabricating a composite part, the method comprising:

laying up a preform that is made of fiber reinforced material and that includes a cavity;

inserting one or more bladders that are loaded with expandable pellets into the cavity;

inserting filler pellets into the cavity that are external to the one or more bladders;

inflating the one or more bladders in response to a triggering condition that increases volumes of the expandable pellets and causes the pellets to force flexible casings of the one or more bladders outward;

consolidating the preform while the one or more bladders are inflated;

deflating the one or more bladders by cooling the one or more bladders; and

removing the one or more bladders from the cavity.

22. The non-transitory computer readable medium of claim 21 wherein:

the method further comprises hardening the preform to form a portion of an aircraft.