galinhdz(at)gmail.com
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 Posted: Fri Aug 14, 2015 5:47 pm Post subject: Lay up |
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THANKS to Charlie for forwarding this post since I did not get it. I was just curious and wondering as to which is the best way to skin this cat. 
On Fri, Aug 14, 2015 at 9:34 PM, Charlie Smith <smith.smithcts(at)gmail.com (smith.smithcts(at)gmail.com)> wrote:
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It was his post on the forum.
PostPosted: Fri Aug 14, 2015 6:02 am Post subject: Fiberglass vs Carbon Fiber for my layup Reply with quote
Hi Galin,
I will be up there soon. Really. I just have a lot of catching up to do.
The choice between carbon and glass is not that simple. Yes, carbon is about 2.5 times as strong and as stiff as glass. But they way they are used actually can have a larger impact on strength and stiffness. For example in bending a solid layup of 10 plies of glass is stronger and stiffer than a solid layup of 5 plies carbon since the glass is twice as thick. Keep in mind that when you double the thickness you about quadruple the bending strength and the stiffness increases about 8 times.
So to replace the 20 total plies of glass you would need a total of about 13 plies of carbon to get the same bending strength. But to get the same bending stiffness you would need about 15 plies of carbon.
Since your repair is more of a local stiffness issue you really need to meet (or beat) the original stiffness.
That being said, since the outer plies are doing more work a glass and carbon sandwich can work very well. But this will require a semi balanced layup with carbon on both sides. Or the original layup in glass with the addition of carbon more as an integrated backing plate.
There are many ways to do this that will work. But if it was me I would also want to make it so it will never happen again. I like 8 plies glass and 3 plies carbon from the outside (bottom) and 10 plies glass and 5 plies carbon from the inside. It can also be done all carbon and this would save about 5 plies total so would maybe be a little neater.
Mark Kettering
Sent from Mail for Windows 10
From: Galin Hernandez
Sent: Friday, August 14, 2015 7:23 PM
To: Charlie Smith
Subject: Re: Lay up
For some reason I did not get Mark's e-mail. Can somebody re-send it. 
On Fri, Aug 14, 2015 at 7:07 PM, Charlie Smith <smith.smithcts(at)gmail.com (smith.smithcts(at)gmail.com)> wrote: | Quote: |
Galin,
Mark’s advice seems on target to me. I’d take it if he were offering it to me. Just remember that the failure wasn’t caused by a lack of strength of the composite. The metal washer was over stressed so it rightly was a failure of the metal components and the rubber barrier. The rest happened due to fretting and that will happen if metal rubs against composite materials (carbon or glass) regardless of thickness. The thickness will only change the time it takes to wear through.
Charlie
Sent from Mail for Windows 10
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