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Technical Discussions
Emil Hasl
Emil Hasl
07:23 May-19-2001
Fiber orientation in SMC

I am in search of a nondestructive test method to view, or at least detect bad flow conditions, voids and delaminations in a SMC part.
The composite is a vinyl ester based sheet molding compound.
It has 63% glass fiber content, and the glass fibers are 1" long.
The density of the glass is 2,6 g/cm3.
The density of the matrix is 1,15 g/cm3.

I am not interested in checking the whole part, it is pretty large, the total mass is 10kg.
The thickest section I neeed to check is about 25mm thick.

Is anyone aware of a commercially available system for checking something like this?

Thank you!
Emil Hasl
Mechanical Engineer

Tom Nelligan
retired, USA, Joined Nov 1998, 390

Tom Nelligan

Joined Nov 1998
05:05 May-21-2001
Re: Fiber orientation in SMC
: I am in search of a nondestructive test method to view, or at least detect bad flow conditions, voids and delaminations in a SMC part.

It may be possible to find these conditions using a number of commercially available ultrasonic flaw detectors with low frequency transducers. Certainly voids and delaminations will be detectable if they're large enough. Minimum detectable void/delamination size would have to be determined experimentally, and will depend on the sound transmission properties of the material, but it's probably on the order of five or six millimeters. If your particular material is excessively attenuating or scattering the minimum detectable flaw size will be higher.

As for fiber misorintation, I would look at sound velocity and attenuation in good and band samples and see if there are changes that correlate with the condition you're looking for. That test is often useful with graphite/epoxy composites and it may be applicable to your material as well.

We'd be happy to examine samples for you if you're interested.

--Tom Nelligan
Panametrics, Inc.


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