Speedbump59
I am guessing that you have never been involved In composite repair because you simply lack understanding of the subject, the company that I am involved with has been involved with the maintenance and repair of aeronautical composite structures since the late 1960's and myself have been involved since the early 90's. I am the guy who puts his name to the release to service paperwork......... We have yet to have a structural problem with an aircraft we have repaired.
Unlike a metal repair were you aim to have the edges of the repair very smooth to avoid inducing a fatigue crack the surfaces of a scarf joint are comparably rough and I am sure that under a microscope the fibers would look fluffy. This results in both sides of the repair being slightly porus, this allows the resin to soak into both sides of the repair and the fibers to intermingle within the joint in the same was as within the original structure.
As I have said before all critical structural repairs are subject to samples being tested to distruction by the original manufactures, these samples usually fail at 1-3 % above the average fail point for new items........ We have never had a test sample fail to meet the new specification.
The fact of the matter is that Boeing would never have built an aircraft structure using a totaly new Technology, composite structure has been about in aviation for 50 years now and bonding Technology since the Wright brothers, metal bonding since the DH Comet and Dove so the techniques for repair are well understood by all except the metalcentrics.
I have no idea what Boeing are planning for this repair but if it is not a scaf respair the wieght will go up for little structural advantage,