Just a heads up, using epoxy resin and mat together is a bad idea. The epoxy is way to thick and you will shred the mat trying to wet it out and work out any air especially with limited lay up experience


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. Never had a issue with epoxy and mat


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It has to do with the bonding agent in the mat not dissolving and causing the mat to keep its form.

Normally very noticeable when trying to contour.

GT

.  I still have never had a problem. But I guess you could from what you are saying. But we were talking about a flat 3" wide patch  I like the bond you get with it for the hard to get to areas where prep maybe questionable. JMO


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.  I still have never had a problem. But I guess you could from what you are saying. But we were talking about a flat 3" wide patch  I like the bond you get with it for the hard to get to areas where prep maybe questionable. JMO

The problem is actually with the resin bonding properly to the fibers.  The styrene-based adhesive used to hold the short fibers (while on the roll) dissolves in polyester resin during the wetting out process.  This doesn't happen with epoxy.  The styrene-based adhesive does not dissolve and will actually act like a masking agent causing the epoxy to bond to it rather than to the actual fibers.

Improper bonding to the fibers reduces the overall tensile strength of the part because the fibers are not properly supported in the resin/fiber matrix.  The fibers actually have a a higher tensile strength than the resin.  The tensile strength of the finished product is an average of the the that of the fibers and resin.  If the fibers are not bonded properly, they can actually pull through the resin on failure.