Talk Composites - The Forum for Advanced Composites

First infusion has porosity

http://www.talkcomposites.com/Topic23186.aspx

By Roo2 - 4/24/2017 7:13:27 AM

Hello there,
I've just completed my first infused part. It's a shell for a home made metal detector coil. I'm generally happy with the result but would like to improve the surface finish on future parts.
The part is made with 2 layers of 200gsm fibreglass and a low viscosity epoxy that uses a very slow hardener. It took over 4 hours to start to gel in a warm environment. I'm using a pump that can get down to about -28" and  after I infused the resin it was turned off. No evidence of leaks where seen and the vacuum gauge needle didn't move for the entire cure duration.
If you look at the attached photo of the shell on the scales there are a few areas that appear to have porosity. Small holes between the fibre weave. Could that be caused by using hardener that is too slow and all the resin has been squeezed, drawn out of the very thin laminate? Or is it just evidence of tiny air leaks I couldn't see or measure?
Thanks
By Warren (Staff) - 5/2/2017 9:49:52 AM

Also remember there will be some small amount of air in the fabric that comes out during the infusion process.  You always introduce a little bit through the resin feed  line initially.