Process method to repair bismaleimide (BMI) composite structures

• US 20030188821A1
• Filed: 04/09/2002
• Published: 10/09/2003
• Est. Priority Date: 04/09/2002
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Owen, Wesley S., Keller, Russell L.
• Granted Patent: US 6,761,783 B2
• Time in Patent Office: Days
• US Class Current: 156/94
• CPC Class Codes: B29C 2043/3644 Vacuum bags; Details thereof, e.g. fixing or clamping
• CPC Class Codes: B29C 43/12 using bags surrounding the moulding material or using membranes contacting the moulding material
• CPC Class Codes: B29C 43/203 Making multilayered articles
• CPC Class Codes: B29C 73/10 using patches sealing on the surface of the article B29C73/14 takes precedence
• CPC Class Codes: B29C 73/34 for local heating
• CPC Class Codes: B29L 2031/3076 Aircrafts blades, propellers B29L2031/08
• CPC Class Codes: B29L 2031/3082 Fuselages
• CPC Class Codes: B29L 2031/3085 Wings

Abstract

A method for repairing a damaged area, referred to as the repair area, of a composite structure comprises steps of: making alignment markings on the repair area; fabricating a pair of alignment templates; preparing the repair area for a hot bonded, vacuum bagged repair; assembling a repair patch; consolidating the repair patch; heating the repair patch; transferring and aligning the repair patch to the repair area; vacuum bagging, heating, and cooling the repair patch for a partial cure at the repair area; heating and cooling the repair patch in an oven; and bonding the repair patch to the repair area.

Claims

1. A method for repairing a damaged repair area of a composite structure, comprising steps of:

making alignment markings on the repair area;

fabricating a pair of alignment templates;

preparing the repair area for a hot bonded, vacuum bagged repair;

assembling a repair patch;

consolidating said repair patch;

heating said repair patch;

transferring and aligning said repair patch to the repair area;

vacuum bagging, heating, and cooling said repair patch at the repair area;

heating and cooling said repair patch in an oven; and

bonding said repair patch to the repair area.

2. The method of claim 1 further comprising a step, before said step of making alignment markings, of preparing the repair area wherein damaged material is removed from the repair area and a surface of the repair area is cleaned.

3. The method of claim 1 wherein said step of making alignment markings comprises marking a hinge line and a 90°

line.

4. The method of claim 1 wherein said fabricating step comprises steps of centering a piece of transparent bagging film over the repair area;

and tracing said alignment markings onto said transparent bagging film.

5. The method of claim 1 wherein said preparing step comprises steps of:

installing thermocouples in the repair area;

removing a flash tape in a bond area of the repair area and leaving the flash tape outside of the bond area; and

covering the repair area with a solid separator film.

6. The method of claim 5 wherein said assembling step comprises:

cutting to size plies of fiber-reinforced BMI repair material;

fabricating a ply lay-up template;

taping a first of said pair of alignment templates on said ply lay-up template;

laying up said plies on said first of said pair of alignment templates; and

affixing a second of said pair of alignment templates to said repair material.

7. The method of claim 1 wherein said consolidating step comprises steps of:

covering a center area of a plate with an insulation;

covering said insulation with a heating blanket;

placing a thin copper sheet over said heating blanket;

covering said copper sheet with a non-porous separator film;

transferring said repair patch onto said non-porous separator film;

removing one of said pair of alignment templates from said repair patch;

placing thermocouples around said repair patch;

placing a porous separator film onto said repair patch;

placing a pricked non-porous separator film onto said porous separator film;

placing a first fiberglass cloth over said pricked non-porous separator film;

vacuum bagging said insulation, said heating blanket, said copper sheet, said non-porous separator film, said repair patch with one of said pair of alignment templates, said thermocouples, said porous separator film, said pricked non-porous separator film, and said first fiberglass cloth using a lower vacuum bag;

applying a first vacuum to said lower vacuum bag;

placing a second fiberglass cloth onto said lower vacuum bag;

placing a rigid box onto said second fiberglass cloth wherein said rigid box is substantially centered over said repair patch;

placing a third fiberglass cloth over said rigid box;

vacuum bagging said rigid box using an upper vacuum bag; and

applying a second vacuum to said upper vacuum bag, wherein said second vacuum is at a level ranging between zero inches to approximately one inch of mercury less than said first vacuum.

8. The method of claim 7 wherein said heating step comprises:

heating said repair patch at a rate of 3°

F. per minute to approximately 250°

F.;

holding said repair patch at approximately 250°

F. for approximately 15 minutes;

releasing said second vacuum from said upper vacuum bag, opening said upper vacuum bag, and removing said rigid box;

said third fiberglass cloth, and said second fiberglass cloth;

holding said repair patch at approximately 250°

F. for approximately 15 minutes; and

removing said repair patch from said lower vacuum bag.

9. The method of claim 6 wherein said transferring and aligning step comprises:

transferring said repair patch to the repair area;

aligning one of said pair of alignment templates with said alignment markings on the repair area; and

rotating said repair patch to contact said solid separator film covering the repair area; and

removing said one of said pair of alignment templates from said repair patch.

10. The method of claim 1 wherein said vacuum bagging, heating, and cooling step comprises:

placing a precut perforated separator film over the repair patch;

placing a fourth fiberglass cloth over said precut perforated separator film;

placing a second solid separator film over said fourth fiberglass cloth;

placing a heat blanket over said second solid separator film;

placing a fifth fiberglass cloth over said heat blanket;

vacuum bagging said repair patch;

heating said repair patch at a rate of 3°

F. per minute to approximately 350°

F.;

holding said repair patch at approximately 350°

F. for approximately 3 hours; and

cooling said repair patch at a rate of 3°

F. per minute to approximately ambient temperature.

11. The method of claim 1 wherein said heating and cooling step comprises:

marking orientation on the repair patch;

removing the repair patch from the repair area;

placing the repair patch in an oven;

heating said repair patch at a rate of 3°

F. per minute to approximately 375°

F.;

holding said repair patch at approximately 375°

F. for approximately 3 hours;

heating said repair patch at a rate of 3°

F. per minute to approximately 440°

F.;

holding said repair patch at approximately 440°

F. for approximately 6 hours; and

cooling said repair patch at a rate of 3°

F. per minute to approximately ambient temperature.

12. A method for repairing a damaged repair area of a composite structure, comprising steps of:

making alignment markings on the repair area;

fabricating a pair of alignment templates;

preparing the repair area for a hot bonded, vacuum bagged repair by;

installing thermocouples in the repair area,

removing a flash tape in a bond area of the repair area and leaving the flash tape outside of the bond area, and

covering the repair area with a solid separator film;

assembling a repair patch by;

cutting to size plies of fiber-reinforced BMI repair material,

fabricating a ply lay-up template,

taping a first of said pair of alignment templates on said ply lay-up template,

laying up said plies on said first of said pair of alignment templates, and

affixing a second of said pair of alignment templates to said repair material;

consolidating said repair patch;

heating said repair patch;

transferring and aligning said repair patch to the repair area by;

transferring said repair patch to the repair area,

aligning one of said pair of alignment templates with said alignment markings on the repair area,

rotating said repair patch to contact said solid separator film covering the repair area, and

removing said one of said pair of alignment templates from said repair patch;

vacuum bagging, heating, and cooling said repair patch at the repair area;

heating and cooling said repair patch in an oven; and

bonding said repair patch to the repair area.

13. The method of claim 12 further comprising a step, before said step of making alignment markings, of preparing the repair area wherein damaged material is removed from the repair area and a surface of the repair area is cleaned.

14. The method of claim 12 wherein said step of making alignment markings comprises marking a hinge line and a 90°

line.

15. The method of claim 12 wherein said step of fabricating alignment templates comprises steps of centering a piece of transparent bagging film over the repair area;

and tracing said alignment markings onto said transparent bagging film.

16. The method of claim 12 wherein said consolidating step comprises steps of:

covering a center area of a plate with an insulation;

covering said insulation with a heating blanket;

placing a thin copper sheet over said heating blanket;

covering said copper sheet with a non-porous separator film;

transferring said repair patch onto said non-porous separator film;

removing one of said pair of alignment templates from said repair patch;

placing thermocouples around said repair patch;

placing a porous separator film onto said repair patch;

placing a pricked non-porous separator film onto said porous separator film;

placing a first fiberglass cloth over said pricked non-porous separator film;

vacuum bagging said insulation, said heating blanket, said copper sheet, said non-porous separator film, said repair patch with one of said pair of alignment templates, said thermocouples, said porous separator film, said pricked non-porous separator film, and said first fiberglass cloth using a lower vacuum bag;

applying a first vacuum to said lower vacuum bag;

placing a second fiberglass cloth onto said lower vacuum bag;

placing a rigid box onto said second fiberglass cloth wherein said rigid box is substantially centered over said repair patch;

placing a third fiberglass cloth over said rigid box;

vacuum bagging said rigid box using an upper vacuum bag; and

applying a second vacuum to said upper vacuum bag, wherein said second vacuum is at a level ranging between zero inches through approximately one inch of mercury less than said first vacuum.

17. The method of claim 16 wherein said heating step comprises:

heating said repair patch at a rate of 3°

F. per minute to approximately 250°

F.;

holding said repair patch at approximately 250°

F. for approximately 15 minutes;

releasing said second vacuum from said upper vacuum bag, opening said upper vacuum bag, and removing said rigid box;

said third fiberglass cloth, and said second fiberglass cloth;

holding said repair patch at approximately 250°

F. for approximately 15 minutes; and

removing said repair patch from said lower vacuum bag.

18. The method of claim 12 wherein said vacuum bagging, heating, and cooling step comprises:

placing a precut perforated separator film over the repair patch;

placing a fourth fiberglass cloth over said precut perforated separator film;

placing a second solid separator film over said fourth fiberglass cloth;

placing a heat blanket over said second solid separator film;

placing a fifth fiberglass cloth over said heat blanket;

vacuum bagging said repair patch;

heating said repair patch at a rate of 3°

F. per minute to approximately 350°

F.;

holding said repair patch at approximately 350°

F. for approximately 3 hours; and

cooling said repair patch at a rate of 3°

F. per minute to approximately ambient temperature.

19. The method of claim 12 wherein said heating and cooling step comprises:

marking orientation on the repair patch;

removing the repair patch from the repair area;

placing the repair patch in an oven;

heating said repair patch at a rate of 3°

F. per minute to approximately 375°

F.;

holding said repair patch at approximately 375°

F. for approximately 3 hours;

heating said repair patch at a rate of 3°

F. per minute to approximately 440°

F.;

holding said repair patch at approximately 440°

F. for approximately 6 hours; and

cooling said repair patch at a rate of 3°

F. per minute to approximately ambient temperature.

20. A method for repairing a damaged repair area of a composite structure, comprising steps of:

making alignment markings on the repair area;

fabricating a pair of alignment templates by centering a piece of transparent bagging film over the repair area and tracing said alignment markings onto said transparent bagging film;

preparing the repair area for a hot bonded, vacuum bagged repair by;

installing thermocouples in the repair area,

removing a flash tape in a bond area of the repair area and leaving the flash tape outside of the bond area, and

covering the repair area with a solid separator film;

assembling a repair patch by;

cutting to size plies of fiber-reinforced BMI repair material,

fabricating a ply lay-up template,

taping a first of said pair of alignment templates on said ply lay-up template,

laying up said plies on said alignment template, and

affixing a second of said pair of alignment templates in an alignment template assembly to said repair material;

consolidating said repair patch by;

covering a center area of a plate with an insulation,

covering said insulation with a heating blanket,

placing a thin copper sheet over said heating blanket,

covering said copper sheet with a non-porous separator film,

transferring said repair patch onto said non-porous separator film, largest ply down,

removing one of said pair of alignment templates from said repair patch,

placing thermocouples around said repair patch,

placing a porous separator film onto said repair patch,

placing a pricked non-porous separator film onto said porous separator film,

placing a first fiberglass cloth over said pricked non-porous separator film,

vacuum bagging said insulation, said heating blanket, said copper sheet, said non-porous separator film, said repair patch with said alignment template assembly, said thermocouples, said porous separator film, said pricked non-porous separator film, and said first fiberglass cloth using a lower vacuum bag,

applying a first vacuum to said lower vacuum bag,

placing a second fiberglass cloth onto said lower vacuum bag,

placing a rigid box onto said second fiberglass cloth wherein said rigid box is substantially centered over said repair patch,

placing a third fiberglass cloth over said rigid box,

vacuum bagging said rigid box using an upper vacuum bag, and

applying a second vacuum to said upper vacuum bag, wherein said second vacuum is at a level ranging between zero inches through approximately one inch of mercury less than said first vacuum;

heating said repair patch by;

heating said repair patch at a rate of 3°

F. per minute to approximately 250°

F.,

holding said repair patch at approximately 250°

F. for approximately 15 minutes,

releasing said second vacuum from said upper vacuum bag, opening said upper vacuum bag, and removing said rigid box;

said third fiberglass cloth, and said second fiberglass cloth,

holding said repair patch at approximately 250°

F. for approximately 15 minutes, and

removing said repair patch from said lower vacuum bag;

transferring and aligning said repair patch to the repair area by;

transferring said repair patch to the repair area, aligning said alignment template assembly with said alignment markings on the repair area,

rotating said repair patch to contact said solid separator film covering the repair area, and

removing said alignment template assembly from said repair patch;

vacuum bagging, heating, and cooling said repair patch at the repair area by;

placing a precut perforated separator film over the repair patch,

placing a fourth fiberglass cloth over said precut perforated separator film,

placing a second solid separator film over said fourth fiberglass cloth,

placing a heat blanket over said second solid separator film,

placing a fifth fiberglass cloth over said heat blanket,

vacuum bagging said repair patch,

heating said repair patch at a rate of 3°

F. per minute to approximately 350°

F.,

holding said repair patch at approximately 350°

F. for approximately 3 hours, and

cooling said repair patch at a rate of 3°

F. per minute to approximately ambient temperature;

heating and cooling said repair patch in an oven by;

marking orientation on the repair patch;

removing the repair patch from the repair area,

placing the repair patch in an oven,

heating said repair patch at a rate of 3°

F. per minute to approximately 375°

F.,

holding said repair patch at approximately 375°

F. for approximately 3 hours,

heating said repair patch at a rate of 3°

F. per minute to approximately 440°

F.,

holding said repair patch at approximately 440°

F. for approximately 6 hours, and

cooling said repair patch at a rate of 3°

F. per minute to approximately ambient temperature; and

bonding said repair patch to the repair area.

21. The method of claim 20 further comprising a step, before said step of making alignment markings, of preparing the repair area wherein damaged material is removed from the repair area and a surface of the repair area is cleaned.

22. The method of claim 20 wherein said step of making alignment markings comprises marking a hinge line and a 90°

line.