Hi All,

This week I've made some carbon infused door cards. The first 2 out of 4 had defects in a number of random locations but always only on an internal radius and never on a flat, between the duratec sunshield and 1st layer. I'm very certain these arn't due to bridging as I am very cautious and use an assortment of dibbers. Knowing I had an acceptable level of vacuum (3mbar absolute and 5mbar on the other card) with a leak drop test of less than 5mbar/hour I'm certain it isn't an air leak. Also, if it were bridging, it should have just filled the void with resin. I put these defects down to using a different brand of track spray that must have been incompatible.

The second set I made I went back to using tried and tested aerofix3 spray tack, being extra cautious to use the slightest mist and no bridging. However the same results. I've referenced close up pictures against other defects I've had in previous years and they look totally different. I don't believe they are air, but more to do with moisture. A few things to note are is that leaving the part overnight the cloudiness of the 'bubble' disappears and it's less noticeable, like it has evaporated somehow. I've been using Sunshield for awhile now and these parts were sprayed in 25*c, late afternoon and left overnight before I layed up the following morning then infused the morning after (38hours). Part was clean, with no chance of contamination on the surface.
Attached are two images of the new 'moisture bubbles' and the picture with the 12k tow is from a previous job that trapped some air. They look quite different.

Any ideas? Thanks.

Well if you think its moisture you can dry your fabric in an oven, and leave your part under vacuum longer to remove the moisture. The void in the corner looks like a slight bridge, but hard to tell from the photo. Are you degassing your resin before and after mixing the resin? Epoxy resin sucks up moisture. If the container has been open for awhile (and especially not sealed well) it will absorb moisture over time. You can put the resin (unmixed) in a bucket and degass it at higher temps (50-60C), for a couple hours.