Forming of staged thermoset composite materials

Patent metadata

Field	Value
Publication number	US-9539767-B2
Application number	US-201414561900-A
Country	US
Kind code	B2
Filing date	Dec 5, 2014
Priority date	Dec 5, 2014
Publication date	Jan 10, 2017
Grant date	Jan 10, 2017

Abstract

A method of forming a composite article may include 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. The method may initially include heating the initially-cured composite laminate to an intermediate temperature higher than the initial temperature and above a resin glass transition temperature. In addition, the method may include 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. Furthermore, the method may include 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.

First claim

What is claimed is:

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.

Assignees

• Boeing Co

Inventors

• Butler Geoffrey A

Classifications

• B29C35/02

  Heating or curing, e.g. crosslinking or vulcanizing {during moulding, e.g. in a mould}(cold vulcanisation B29C35/18 {; vulcanising tyres, presses therefor B29D30/0601}) · CPC title

• B29K2105/243

  Partially cured · CPC title

• B29C73/10

  using patches sealing on the surface of the article (B29C73/14 takes precedence) · CPC title

• B29C70/30 Primary

  Shaping by lay-up, i.e. applying fibres, tape or broadsheet on a mould, former or core; Shaping by spray-up, i.e. spraying of fibres on a mould, former or core · CPC title

• B29C70/44

  using isostatic pressure, e.g. pressure difference-moulding, vacuum bag-moulding, autoclave-moulding or expanding rubber-moulding · CPC title