ORIGINAL: davidfee
The way I've done the peel ply skin hinges, the peel ply (dacron/nylon fabric) goes between the outer glass (or carbon, whatever) layers and the core material. The epoxy which penetrates the peel ply acts like a million tiny rivets holding the whole thing together. There is a ton of bonding area, relatively speaking.
If you think about the loads on the hinge, you can break them down into shear and tension loads. In shear, there's no way you're ever going to pull the hinge out with flight loads... the core material would fail first. In tension, practice peeling up a fully saturated strip of peel ply from a cured laminate. First you have to get it started... and then the forces required are still very much greater than anything a flying surface will see in use.
I hear you saying that, I know how tough it can sometimes be to separate a peel ply, still in my mind I see the thousands of times that hinge will flex and I couldn't use peel ply. Glass or better kevlar so you don't cut it making the score. That's just me, you understand.
The trick is to scribe through the outer layers of glass/carbon/epoxy and stop just shy of the peel ply. Then scribe the inside also (need to cut the lower surface free first). Then you gently flex the hinge to fracture the epoxy along the hingeline. The more you flex, the more free the hinge becomes. I typically cut the peel ply on a bias to further reduce hinge stiffness.
Ah, so you do have to fracture the matrix. I couldn't see...... I'd have to lay it all up with whatever I need for the wing and control surface and then just one ply of kevlar for the hinge. To lay up the wing and control surface as one lamination I'd have to have some kind of precision machine to cut through all but one layer of laminate and leave the last one intact. Again, that's just me.
Also I couldn't see how to keep the matrix out of the hinge cloth. I figured I'd have to just score and break it like cutting a piece of window glass.
As you say, just go make one. It helps to boot El Diablo out of the details.
