Process method to repair bismaleimide (BMI) composite structures

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 bismaleimide 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 assembled repair patch;
• heating said consolidated repair patch;
• transferring and aligning said consolidated and heated 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 transferred and aligned repair patch at the repair area;
• removing said bagged, heated and cooled repair patch from the repair area heating and cooling said removed repair patch in an oven;
• and
• bonding said oven heated and cooled repair patch to the repair area.

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 bismaleimide 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 assembled repair patch by:
• covering a center area of a plate with 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 consolidated 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 consolidated and heated 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 transferred and aligned 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;
• removing said vacuum bagged, heated and cooled repair patch from the repair area heating and cooling said removed 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 oven heated and cooled repair patch to the repair area.