Cary,
You didnt really give us enough info to give a good answer.
I did talk to a couple of people here where I work (gulfstream aerospace)
who work with composits.
Our composit guy, Steve, said that composits can be checked for
de-laminating with a simple "tap" test. If you tap the composit with a coin
or key, you should hear a sharp tap. If you get to an area that is
de-laminating you will hear a clearly different "thud" kind of sound. He also
said that if you are working with a thin "painted on" type of coating over
metal, the easiest might be to sand it off, check for cracks and "re-paint"
the composit.
His best suggestion for anything critical would be "X-ray".
When I talked to the people in NDT (non destructive testing), they did not
put much faith in ultra-sonic testing. As the waves pass thru 2 different
materials, they deform (picture a straw in a glass of water), making it
difficult to determine the depth and exact location of a crack.
Again, they suggested X-ray as being the best method of testing wether you
have solid composite, laminate over composite, or composite over metal.
Bear in mind that we are working on aircraft, not cars, so we may be a bit
more picky than necessary for whatever part you have in question. If it is
any critical part, however, I would lean toward their suggestions of X-ray.
If you have an aircraft service facility nearby, they may be able to do the
testing for you, or be able to send it out to someone who can. Its not cheap,
but if its something your life (or even the survival of your car) depends on,
its cheap insurance ..
Hope this was of some help...
Tom
http://www.fot-racing.com/spit/caption/tom_strange.htm
#4 white spitfire
--- On Mon, 4/12/10, Group44TR7@aol.com <Group44TR7@aol.com> wrote:
From: Group44TR7@aol.com <Group44TR7@aol.com>
Subject: [Fot] Testing for Composite Cracking ?
To: fot@autox.team.net
Date: Monday, April 12, 2010, 2:46 PM
Guys
What would be the cheapest, but reliable testing method to determine if
crack lines on the surface coating a high performance composite (think
advanced type composite) are simply cosmetic surface coating cracks or are the
surface lines of actual fractures in the underlying composite.
The item being examined is approximately a 1 to 1 1/2 inch diamter
hollow tube with a wall thickness of about 3/8 inch of the composite at the
point of observable lines, the object is about 30 inches long. The item must
not
be damaged by the testing procedure.
Thanks in advance.
Cary
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