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Archive for February, 2016
Posted by lincoln | Feb 16, 2016 @ 06:00 PM | 32,592 Views
This is a reference for this post: https://www.rcgroups.com/forums/show...2&postcount=78

This is just about wing skin stiffness in bending, without the core material.

I remember that, after some time, I couldn't interpret my old notes for experiments I did on this stuff. So I'll do a reality check on this stuff with other people's data. Unfortunately, I didn't find data on epoxy/paper, so I'm using data for phenolic and paper, which ought to be comparable. It's my understanding that the basic grade of phenolic/paper uses kraft paper, which is the paper I'm talking about. Can't be sure of it. Anyway, there's enough uncertainty here that we can't say anything except we may be in the ballpark, or we're not in the ballpark.

Here are the material properties I'm using:
Style 1581 glass cloth with epoxy:
(this cloth is much heavier than you'd use on a wing, but I'd expect that the bulk properties are similar.)
Elastic modulus, flexural: 3.6 mpsi (this seems much higher than other sources but is what the paper says, and may be explained by a higher than usual fiber volume) Seeing as it's nearly as stiff at 280F, the epoxy must be some special stuff
2.0mpsi is what I've usually heard
Flexural strength: the paper only gives ultimate strength, I've usually heard about about 30kpsi yield. This stuff is about 68 kpsi ultimate, but I don't know what it is in yield.
Resin by weight: 33 percent I think usually this number is closer to 40 or 50 percent! Long ago, in MAN...Continue Reading