The technique works as follows. If a small hole or crack appears in an aircraft (for example, due to wear or a tiny solid object hitting the aircraft), from nearby built-in conduits you will need to “bleed” epoxy resin, which will quickly seal the hole, restoring structural integrity. By mixing dye into the resin, any “self-repair” can be seen as a colored patch that can be easily identified during subsequent ground inspections, and a full repair can then be carried out if necessary.
This simple but ingenious technique similar to the process of bleeding and scarring What we see after we sustain a cut hand, for example, has the potential to be applied anywhere in an aircraft where fiber-reinforced polymer composites are used. These lightweight, high-performance materials are becoming increasingly popular, not just in airplanes but also in cars, wind turbines, and even in the manufacture of space vehicles. The new self-repair system could have notable utility in all of these fields.
So this strategy is expected to take care of damage that is not visible to the naked eye and does not present a serious problem. Therefore, it is not intended to replace maintenance routines but to complement them.
Source: Plastic Environment Magazine