Blade tapes and disbonding
Guys
I am aware that there are ADs for some types of blades requiring repaints to supposedly prevent blade disbonding (incorrectly termed delamination). The theory is that the adhesive in the bond between the skin and the spar is eroded sufficiently to cause disbonding. There are also STCs for applying tapes to prevent this erosion of the adhesive.
I have grave doubts that these approaches will be effective. From the evidence I have seen on a number of blades, the failures I have seen are occurring at the interface between the adhesive and the metal. This can not be due to erosion. If an adhesive bond is eroded sufficiently to cause bond failure, then the failure will be cohesion, in other words the adhesive will fracture, leaving some adhesive on both surfaces. It will not cause interfacial (adhesion) failure which results in all the adhesive being left on one surface, or else mixed-mode failure with some adhesion and some cohesion failure.
Interfacial failure is typically related to hydration of the chemical bonds at the interface, and this is a chemical process, not a mechanical process such as erosion.
Having said that, if your aircraft type does not experience disbonding, there may be merit in applying tapes. (I stress that the tapes and paint as well will not prevent interfacial disbonding.) I have seen some of fdr's work and I am impressed by the level of research he has done. I am also impressed by the results he is achieving with his tape system. Not only does it reduce erosion, it improves blade performance. Keep up the good work fdr.
Regards
blakmax