REFLECTOR: Carbon fiber

Ken C. Baker kenb at velocityaircraft.com
Fri May 9 09:07:29 CDT 2008


Alex and Noel,

I was actually going to mention stiffness too - but a lot of factors come
into play there as well. There are some texalium fibers that are even
stiffer than a lot of the carbon that I've seen. And I've used a lot of
legitimate carbon fiber that is softer and more pliable than some of the
e-glass that we use. The 2K carbon twill that we use at the factory right
now is actually much more pliable than 7725 BID. 

"Fake" glasses and low-cost glasses for non-aerospace applications are
sometimes sold as "loom state" goods. That is, they aren't treated with
surface finishes like the Volan-A that our 7725 BID is treated with to allow
proper chemical binding with the resin matrix. As such, the starches from
the weaving process are sometimes left on the raw glass, and the feel is
much stiffer. This is all to say that stiffness isn't necessarily a
fool-proof way of determining whether carbon is fake or not. Comparing
stiffness can certainly be helpful if you're familiar with the fabric weave
style that you intended to buy - but there are so many different weaves,
styles, and surface finishes - it can be difficult to be conclusive. 

Another thing I've noticed - if you take a look at the selvedge edge of
almost all fabrics, there is a twist of fiber that binds together the
structural fibers, so that they do not fray. Most carbon fibers that I've
seen use a yellow kevlar fiber for this purpose. Most e-glass weaves use
another strand of e-glass for this purpose.

Best,

-Ken Baker

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Alex Balic
Sent: Friday, May 09, 2008 8:52 AM
To: 'Velocity Aircraft Owners and Builders list'
Subject: Re: REFLECTOR: Carbon fiber

Also- carbon cloth is very stiff as compared to similar weight glass cloth-
if it handles just like glass, then it probably is.

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Ken C. Baker
Sent: Friday, May 09, 2008 7:28 AM
To: 'Velocity Aircraft Owners and Builders list'
Subject: REFLECTOR: Carbon fiber

Noel,

When Airbus and Boeing started buying up all of the carbon fiber on the
aerospace market there was a severe lack of the stuff for all of the little
guys. This gave a number of the major loom houses and weavers a good reason
to market 'texalium' and other cosmetic fabrics for places where the look of
carbon, but the stiffness and structural properties weren't entirely
necessary. Unfortunately, some people try to pass the stuff off as the real
deal.

Here's one way to tell the difference: In most woven styles of e-glass,
there is a bit of twist in the fiber bundles, whereas with most carbon fiber
weaves there is no twist at all (Carbon has a tendency to lose much of its
structural stiffness if it is twisted at all.) On a roll of carbon fabric,
each of the fiber bundles will appear flat, and almost ribbon-like. It can
be difficult to detect.

Out of curiosity, what are you using the carbon on? 

-Ken Baker
kenb at velocityaircraft.com

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of gattenby at tulsaconnect.com
Sent: Thursday, May 08, 2008 6:07 PM
To: Brett Ferrell; Velocity AircraftOwners and Builders list
Subject: REFLECTOR: Carbon fiber



I was just surfing the Wicks web site...
They have a blurg about someone on e-bay selling "fake carbon fiber bid"
I may have been one of the unlucky,
Anybody got a suggestion as to how to tell "fake" carbon fiber from "real"
carbon fiber?

Noel
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