Hi, does anyone have any ideas on how to maintain stiffness in a single ply of Biaxial glass or carbon epoxy skin? Warping occurs whichever way material is cut, 0/90 or
±45. It is basically a flat panel of roughly 1msq? I would appreciate some help in finding a solution as ply thickness and weight is key.
Do you mean a single sheet of biaxial which is one layer at +45 and the other at -45 or is this a biaxial of woven cloth with one layer ±45 and the other layer 0/90?
Plain weave at 0/90 is the most reliable method of getting a flat piece, however if your stress calcs don’t allow plain weave you would need to use 2 or more finer layers balancing the overall laminate
Yes it is a single ply of biaxial at ±45 but weight and cost are key so building up thinner plies is a non-starter. The saving grace is that the skin will be bonded into a frame so it will stiffen eventually but was hoping for a quick fix to make future skins easier to manage post-cure. Tried panels cut at 0/90 and warping was reduced slightly but still apparent.
In the end, no matter what the material is, somehow, something will have more stress than something else. So it’s VERY hard to avoid warping, unless everything is cured slowly, and the fabric is VERY VERY even.
for post curing, just put a large plate on top of it, or weigh the edges down and do a SLOW ramp up and down.