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Carbon Fiber Roll has Gaps?

rockitdoc

Well Known Member
Sponsor
This is the carbon fiber uni-web I got from ACP Composities. I wasn't expecting the gaps. Is this normal. Obviously, I'm a noob with CF. If normal, won't the gaps affect performance?

Carbon Fiber Uni Web.jpg
 
Carbon fiber

That's weird. Intrested to read what the experts comment.

I just use this stuff. I buy a yard of the 60".
https://www.aircraftspruce.com/pages/me/carbonfiber/bigraphite.php
I cut strips off the width needed. Any fibers get trimmed off and used for carbon fiber flox. I run the rotary cutter back and forth over the scrap fibers. Works great to fill and repair small areas where matching carbon fiber is needed.
 
If I understand the photo, the white lines are places where there's no carbon, and the black stripes are unidirectional carbon with the fibers parallel to the stripes. Assuming this is correct....

The gaps add nothing to the strength or stiffness of your lay up.For loads parallel to the fibers, the lay up will have its strength and stiffness reduced by the percentage of area under the white lines.

For loads perpendicular to the carbon fibers, there's very little strength or stiffness, with or without the white stripes. Uni has only unidirectional effects.

For shear (there's always shear in an airplane structure), uni lay ups have little strength or stiffness by themselves. But if they are oriented in a +/- 45 degree direction, then they are primarily good for shear, but not much for axial loads.

There's little occasion to use uni carbon on an RV. I can think of only two places, really, where they might be remotely useful, and this is as an outer surface ply, inner and exterior, in the area of the cowl-firewall joint, and then only if you're using discrete fasteners like nutplates of Skybolts; and between the hinge and the latch as outer surface plies (also interior and exterior surface plies) on your oil door.

In both cases, use a thin layer of glass as a barrier between any carbon and metals.

In both these cases, bidirectional carbon or unidirectional glass will also suffice.... no point going crazy with this. Uni carbon is one of those things that's best left to people with structural engineering knowledge. Otherwise you're likely adding unnecessary weight, complexity and thickness.

Dave
 
Was curious about it...
From the manufactures website - SKU: XS-UD-CF-2.9-12
Carbon Fiber "Uni-Web" Unidirectional Fiber is a non-woven sheet of unidirectional carbon fibers that can be easily cut without any fraying. Ideal for high strength, weight critical applications. Clearance: Contain Gaps
 
Was curious about it...
From the manufactures website - SKU: XS-UD-CF-2.9-12
Carbon Fiber "Uni-Web" Unidirectional Fiber is a non-woven sheet of unidirectional carbon fibers that can be easily cut without any fraying. Ideal for high strength, weight critical applications. Clearance: Contain Gaps

Yeah, I bought the ‘clearance’ stuff prior to buying this sheet. The previous gaps were much larger. This still has gaps, though. Guess I should have done more diligence!
 
Why are you using unidirectional? Twill weave cloth is the best for whatever an RV builder needs. In fact I would always use glass cloth as it is cheaper and easier to use.
 
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