What are the methods for repairing composite aircraft structures?

Composite repair methods include: Bolted patch (external doubler with fasteners - fastest, adds weight, aerodynamic penalty), Bonded external patch (pre-cured or wet layup, good for minor damage), Bonded scarf repair (removes damage, tapered scarfed edges for load transfer, flush surface), Resin injection (for small delaminations), and Stepped-lap repair (alternative to scarf). Selection factors: damage extent and location, repair category (permanent vs temporary), available facilities, and certification requirements. Repair design uses original laminate strength as target; knockdowns account for repair quality. Hot bonder or autoclave curing may be required. Repair documentation includes NDI verification and return-to-service approval.