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October 2009

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Subject:
From:
Chris Mahanna <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Chris Mahanna <[log in to unmask]>
Date:
Mon, 19 Oct 2009 21:23:52 -0400
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Hello TN,

I'm wondering how certain one can be about the root cause of delam. simply by reading its signature.  Our experience is similar to Paul Reid's (post attached below).  One obvious question: what about when it is both co and adhesive failure?
Are there other features to the signature that are important in determining primary root cause?

Chris

------------------------------------------------------------------------------------------

My sense is that moisture induced delamination presents as adhesive
delamination that is horizontal cracks that resemble blisters and are
located at a laminated interface (b-stage to c-stage or copper, or along
bundles of glass). It may be that the vapor pressure exerted by trapped
moisture induces a mechanical failure at laminated interfaces.

Material degradation induced delamination more often presents as
cohesive failure that may exhibit cracks with vertical sections, often
bifurcating and spanning across b-stage and c-stage material, even
through glass bundles, and tend to propagate with sharper angles. This
failure mode appears to be more a chemical degradation of the epoxy
system.

Sincerely,

Paul Reid


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