Damaged composite structures are definitely repairable, shown clearly in the before and after images below.
However, there are challenges:
Hidden damage issues, including manufacturing defects. (for example, a low velocity impact, which normally wouldn’t cause much damage may cause a sandwich structure to disbond between the skin and core due to poor adhesion during manufacture. If this disbond is the only damage, there may be no visible trace of it from the surface.)
Unexpected damage sources. (for example, an aircraft vertical tail part may be designed to withstand hailstone impact but not able to resist damage from being dropped during shipping or removal for inspection)
“Best” repair techniques are heavily dependent on details of the structure. In other words, because composites excel at being tailored to meet very specific needs, there are few “universal” materials and methods that can be used to achieve successful results. Composite repair specifics really have to be determined on a case-by-case basis.
Basic Repair Process
The very basic fundamentals of composite repair include the following steps: