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Posted for Guy Buchanan <bnn@abac.com>
Subject: Jeffco and Ratio tolerances

Pine,

If you can't get a reply from Jeffco (619-576-9900), I have some basic
information. The Jeffco's "Lancair" system uses its 3102
hardener, which is listed as an aliphatic mannich base hardener. In
general aliphatic hardeners are cross-linking and rely on a
"stoichiometric" mixing ration. Thus, if you supply only 78% of
the hardener required, you will cure only 78% of the available resin.
This sounds worse than it is, because a gross estimate of E/epoxy
bidirectional laminate properties indicates that the bulk properties go
as follows:

Modulus ~ -5% (4.44 Msi to 4.23 Msi)
First ply failure ~ -9% (18.4 ksi to 16.7 ksi)
Ultimate ~ -3% (72.5 ksi to 70 ksi)

Please note that compression properties are notoriously sensitive to resin
stiffness, and my software does not recognize that fact so you could end up
with greater reductions in compression strengths than those noted above.


Respectfully,

Guy Buchanan Buchanan & Newcomer
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