System and method for fabricating and curing large composite structures
A system and method for fabricating large composite fuselages or other vehicle structures, in which the composite structure is fabricated and cured as on a tool, segmented and removed from the tool without disassembling the tool, and then reassembled off the tool to reform the large structure. The tool includes mandrel segments attached to a substructure. The attachments may be moveable to accommodate differential expansion and contraction during curing, and the tool may be rotatable to facilitate access. A composite material of resin and synthetic fibers is applied over the mandrel segments to fabricate the structure on the tool. Caul plates are secured over the composite material, and the composite material is cured on the tool. The resulting structure is cut into part segments which are then removed from the tool, and the part segments are joined to reassemble the large composite structure off the tool.
1. A tool for supporting a large composite part during a fabrication process and a curing process, the tool comprising:
a substructure and a mandrel segment removably attached to the substructure and providing a surface on which the large composite part is fabricated and cured, wherein the substructure is constructed of a first material having a first coefficient of thermal expansion and the mandrel segment is constructed of a second material having a second coefficient of thermal expansion which is different from the first coefficient of thermal expansion;
a first attachment mechanism attaching the mandrel segment to the substructure at a first location and not allowing relative movement between the mandrel segment and the substructure at the first location; and
a second attachment mechanism attaching the mandrel segment to the substructure at a second location and allowing relative movement in at least one direction due to differential thermal expansion between the mandrel segment and the substructure at the second location.
2. The tool of claim 1 , wherein the large composite part has a length of at least five meters and is part of an aircraft fuselage.
3. The tool of claim 1 , the second attachment mechanism comprising an elongated opening which is oriented along a line in a first direction and which allows the relative movement along the line in the first direction due to the differential thermal expansion between the mandrel segment and the substructure at the second location.
4. The tool of claim 1 , the second attachment mechanism comprising an oversized opening which allows the relative movement on a plane in any direction due to the differential thermal expansion between the mandrel segment and the substructure at the second location.
5. The tool of claim 1 , the second attachment mechanism comprising an elongated opening which is oriented along a line in a first direction and which allows the relative movement along the line in the first direction, and the tool further comprising a third attachment mechanism attaching the mandrel segment to the substructure at a third location and comprising an oversized opening which allows the relative movement on a plane in any direction due to the differential thermal expansion between the mandrel segment and the substructure at the third location.
6. The tool of claim 1 , further comprising:
a center hub extending through a longitudinal axis of the substructure;
a first interface element coupled with a first end of the center hub and a second interface element coupled with a second end of the center hub; and
a rotation mechanism coupled with the first and second interface elements and allowing the tool to be rotated about the longitudinal axis.
7. A tool for supporting a large composite part during a fabrication process and a curing process, the tool comprising:
a substructure and a mandrel segment removably attached to the substructure and providing a surface on which the large composite part is fabricated and cured, wherein the substructure is constructed of a first material having a first coefficient of thermal expansion and the mandrel segment is constructed of a second material having a second coefficient of thermal expansion which is lower than the first coefficient of thermal expansion; and
a plurality of attachment mechanisms attaching the mandrel segment to the substructure, each attachment mechanism comprising a first opening associated with the substructure, a second opening associated with the mandrel segment, and a bolt extending through the first and second openings and removably securing the mandrel segment to the substructure, the plurality of attachment mechanisms comprising:
a first attachment mechanism attaching the mandrel segment to the substructure at a first location, wherein the first and second openings of the first attachment mechanism are a same size and a same shape such that the first attachment mechanism does not allow relative movement between the mandrel segment and the substructure at the first location, and
a second attachment mechanism attaching the mandrel segment to the substructure at a second location and allowing relative movement in at least one direction due to differential thermal expansion between the mandrel segment and the substructure at the second location.
8. The tool of claim 7 , wherein at least one of the first and second openings of the second attachment mechanism is elongated along a line in a first direction such that the second attachment mechanism allows the relative movement along the line in the first direction.
9. The tool of claim 7 , wherein at least one of the first and second openings of the second attachment mechanism is larger than the other such that the second attachment mechanism allows the relative movement on a plane in any direction.
10. The tool of claim 7 , the plurality of attachment mechanisms further comprising a third attachment mechanism attaching the mandrel segment to the substructure at a third location and allowing relative movement along a line in at least one direction due to differential thermal expansion between the mandrel segment and the substructure at the third location.
11. The tool of claim 10 , wherein at least the second and third attachment mechanisms are oriented such that the relative movements at the second and third locations are co-planar.
12. The tool of claim 7 , each attachment mechanism further comprising:
a first surface physically associated with the substructure, wherein the first opening extends through the first surface;
a second surface physically associated with the mandrel segment, wherein the second opening extends through the second surface; and
a bushing and a washer fitted over the bolt.
13. The tool of claim 12 , the bushing comprising a sleeve and a flange, and the bushing is fitted over the bolt such that the sleeve extends into the first and second openings and the flange remains above the second surface.
14. The tool of claim 12 , wherein the washer is fitted over the bolt and between the second surface and the flange of the bushing, and the washer maintains a space of between three thousandths of an inch and twelve thousandths of an inch between the washer and the flange of the bushing to facilitate the relative movement of the mandrel segment and the sub structure.
15. The tool of claim 7 , further comprising:
a center hub extending through a longitudinal axis of the substructure;
a first interface element coupled with a first end of the center hub and a second interface element coupled with a second end of the center hub; and
a rotation mechanism coupled with the first and second interface elements and allowing the tool to be rotated about the longitudinal axis.
16. A tool for supporting a large composite part during a fabrication process and a curing process, the tool comprising:
a substructure and a mandrel segment removably attached to the substructure and providing a surface on which the large composite part is fabricated and cured, wherein the substructure is constructed of a first material having a first coefficient of thermal expansion and the mandrel segment is constructed of a second material having a second coefficient of thermal expansion which is lower than the first coefficient of thermal expansion; and
a plurality of attachment mechanisms attaching the mandrel segment to the substructure, with each attachment mechanism comprising a first opening associated with the substructure, a second opening associated with the mandrel segment, and a bolt extending through the first and second openings and removably securing the mandrel segment to the substructure, the plurality of attachment mechanisms comprising:
a first attachment mechanism attaching the mandrel segment to the substructure at a first location, wherein the first and second openings of the first attachment mechanism are a same size and a same shape such that the first attachment mechanism does not allow relative movement between the mandrel segment and the substructure at the first location,
a second attachment mechanism attaching the mandrel segment to the substructure at a second location and allowing relative movement along a line in a particular direction due to differential thermal expansion between the mandrel segment and the substructure at the second location, and
a third attachment mechanism attaching the mandrel segment to the substructure at a third location and allowing relative movement on a plane in any direction due to differential thermal expansion between the mandrel segment and the substructure at the third location,
wherein at least the second and third attachment mechanisms are oriented such that the relative movements at the second and third locations are co-planar.
17. The tool of claim 16 , wherein at least one of the first and second openings of the second attachment mechanism is elongated along the line in the particular direction such that the second attachment mechanism allows the relative movement along the line in the particular direction.
18. The tool of claim 16 , wherein at least one of the first and second openings of the third attachment mechanism is larger than the other such that the third attachment mechanism allows the relative movement on the plane in any direction.
19. The tool of claim 16 , each attachment mechanism further comprising:
a first surface physically associated with the substructure, wherein the first opening extends through the first surface;
a second surface physically associated with the mandrel segment, wherein the second opening extends through the second surface;
a bushing fitted over the bolt, the bushing comprising a sleeve and a flange and fitted over the bolt such that the sleeve extends into the first and second openings and the flange remains above the second surface; and
a washer fitted over the bolt and between the second surface and the flange of the bushing, the washer maintaining a space of between three thousandths of an inch and twelve thousandths of an inch between the washer and the flange of the bushing to facilitate the relative movement of the mandrel segment and the substructure.
20. The tool of claim 16 , further comprising:
a center hub extending through a longitudinal axis of the substructure;
a first interface element coupled with a first end of the center hub and a second interface element coupled with a second end of the center hub; and
a rotation mechanism coupled with the first and second interface elements and allowing the tool to be rotated about the longitudinal axis.