Forming of staged thermoset composite materials

1. A method of forming a composite article, comprising:

initially curing a composite laminate at an initial temperature to an initial cure stage of 30-50 percent of full cure and beyond a gel point to form an initially-cured composite laminate;

heating the initially-cured composite laminate to an intermediate temperature higher than the initial temperature and above a resin glass transition temperature;

intermediately curing the composite laminate to an intermediate cure stage of 50-70 percent of full cure while on a final forming tool to form an intermediately-cured composite laminate;

removing the intermediately-cured composite laminate from the final forming tool; and

finally curing the intermediately-cured composite laminate at a final temperature higher than the intermediate temperature to a final cure stage.

2. The method of claim 1 , further including the step of:

laying up the composite laminate on a flat initial forming tool prior to initially curing the composite laminate.

3. The method of claim 1 , further including the step of:

laying up multiple plies of thermoset prepreg to form the composite laminate prior to initially curing the composite laminate.

4. The method of claim 1 , further including the step of:

laying up multiple plies of dry fiber; and

infusing the plies with resin to form the composite laminate prior to initially curing the composite laminate.

5. The method of claim 1 , further including the step of:

consolidating the composite laminate prior to and/or during the initially curing of the composite laminate.

6. The method of claim 5 , wherein the step of consolidating includes:

consolidating the composite laminate with vacuum pressure applied by a bagging assembly.

7. The method of claim 1 , further including the step of:

trimming the initially-cured composite laminate into a perimeter shape prior to intermediately curing the composite laminate.

8. The method of claim 1 , wherein the step of heating the initially-cured composite laminate to the intermediate temperature comprises:

heating the initially-cured composite laminate to at least approximately 20 degrees F. above the resin glass transition temperature.

9. The method of claim 1 , wherein the step of initially curing the composite laminate comprises:

initially curing the composite laminate to approximately 40 percent of full cure.

10. The method of claim 1 , wherein the step of intermediately curing the composite laminate comprises:

intermediately curing the composite laminate to 60 percent of full cure.

11. A method of reworking an existing composite structure, comprising:

heating a thermoset composite laminate to an initial temperature for an initial dwell time period;

initially curing the composite laminate at the initial temperature to an initial cure stage of 30-50 percent of full cure and beyond a gel point to form an initially-cured composite laminate;

heating the initially-cured composite laminate to a temperature higher than the initial temperature and above a resin glass transition temperature;

forming the initially-cured composite laminate at the higher temperature to a contour of an existing composite structure; and

finally curing the composite laminate at the higher temperature to a final cure stage with the composite laminate conformed and joined to the contour of the existing composite structure.

12. The method of claim 11 , wherein the step of heating the composite laminate to the temperature higher than the initial temperature and finally curing the composite laminate includes:

heating the composite laminate to an intermediate temperature and holding for an intermediate dwell time during forming of the composite laminate to the contour; and

directly ramping from the intermediate temperature to a final temperature above the intermediate temperature to finally cure the composite laminate.

13. The method of claim 11 , further including the step of:

consolidating the composite laminate prior to and/or during the initially curing of the composite laminate.

14. The method of claim 13 , wherein the step of consolidating includes:

consolidating the composite laminate with vacuum pressure applied by a bagging assembly.

15. The method of claim 11 , wherein the step of initially curing the composite laminate comprises:

initially curing the composite laminate to approximately 40 percent of full cure.

16. The method of claim 11 , further including the step of:

trimming the initially-cured composite laminate into a perimeter shape to form a patch complementary to a rework area of the existing composite structure.

17. The method of claim 16 , wherein the step of trimming the initially-cured composite laminate into a patch includes:

machining an edge treatment onto a perimeter edge of the patch to match a scarf angle formed in the rework area of the existing composite structure.

18. The method of claim 11 , wherein the step of heating the initially-cured composite laminate comprises:

heating the initially-cured composite laminate to at least approximately 20 degrees F. above the resin glass transition temperature.

19. The method of claim 11 , further including the step of:

laying up multiple plies of thermoset prepreg to form the composite laminate prior to initially curing the composite laminate.

20. A method of reworking an existing composite structure, comprising:

heating a composite laminate to an initial temperature;

initially curing the composite laminate at the initial temperature to an initial cure stage of 30-50 percent of full cure and beyond a gel point to form an initially-cured composite laminate;

heating the composite laminate to an intermediate temperature and holding for an intermediate dwell time while forming to a contour of the existing composite structure;

ramping up the temperature of the composite laminate from the intermediate temperature to a final temperature above the intermediate temperature and holding for a final dwell time; and

finally curing the composite laminate at the final temperature to a final cure stage while bonding to the existing composite structure during the final dwell time.