Composite Patch Vacuum-mold Repair System Transferred to Commercial Industry

Prior to the development of vacuum-mold repair, the most effective way to repair metal aircraft structures depleted from excessive wear and fatigue or damaged in combat was to fly the aircraft to a maintenance depot or complete the repairs at a field location using conventional splash-mold techniques. Splash-mold techniques, using plastic or ceramic curing compounds, are effective in repairing multiple contour structures; however, they are also costly and time-consuming, since they requireone-time use molds. Splash-mold techniques require large quantities of repair materials to complete several repairs. They also necessitate an unacceptably longdowntime of an equivalent undamaged aircraft while the mold is curing. Another disadvantage of splash-mold techniques is that the compositematerial handling and processing methods employed require cold storageof materials using “clean room” equipment that is bulky, heavy, expensive,and requires extensive training and experience. Transport of aircraft to maintenance depots for metal aircraft structure repair is very expensiveand often creates logistics problems, since maintenance workers work the repairs in around periodic maintenance already scheduled or in progress. VMRS employs a mechanically hardened tooling technique that uses a sealed rubber bag containing lightweight granular filler. Once positioned over the damage location of an equivalent aircraft, the maintenance technician draws a vacuum within the bag, which causes the rubber skin to constrict on the filler, locking it in a firm arrangement and replicatingthe surface geometry of the damage location.