Hi Chris,
While I agree with the basic 'signature'-based root cause assignment as described by Paul, I do not agree that moisture-induced delam is primarily adhesive. 
I have seen more cohesive delams from both causes than adhesive ones.
Werner


 


 

-----Original Message-----
From: Chris Mahanna <[log in to unmask]>
To: [log in to unmask]
Sent: Mon, Oct 19, 2009 9:23 pm
Subject: [TN] delamination signatures










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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