I am including pictures of what all of my composite parts are looking like when held to the light. The parts are made of a single layer of twill weave using the vac-bag method. The parts also look weird ( see last picture ). http://imgur.com/a/Natni
I am editing my first response here
some questions- what material are you using(SP, newport) and what resin content?
what type of mold surface are you laying up on
and what is the vac stack?
it looks to me that the laminate is dry and I will bet you are using a dry peel ply.
If you use 1 layer of twill that is 42% resin and dry peel ply the peel ply will absorb way to much resin leaving the fibers dry. Thats not even getting into the breather material which is sucking out even more.
To you have access to teflon peel ply or better yet pre-preg peel ply.
These pics are of a single layer of SP 200 gm twill laid up on an aluminum plate covered with teflon peel ply and vac stack consisting of pre-preg peel ply, p31 release film and 4 oz breather.
Cure cycle was 4 hours at 100 c, 28 inches of vac.
the only difference in the pic is that the flash is on
What do you mean by balanced laminate
balanced laminate is a laminate that is mirrored top to bottom, after thinking about it this doesnt seem to be the problem here.
Is this moulding off a composite mould? if so then I find this quite normal.
Metal moulds work much better for a vacuum only process or use PTFE.
There is a relation between the surface voids and the fact that you can see through the laminate.
I find that spread tow fabrics like the Primetex fabrics Hexcel uses in their prepregs have less void content on the surface. Im assuming thats because the fibres are filling the gaps so the resin doesn’t have to, therefore it goes to the surface. Laws of physics dictate that any molecule will take the easiest path. If there is gaps between tows, the resin will go there.
As far as structural performance, I don’t think it makes a massive difference.
But to help you, you need to give more info about the materials used, breather stack, bagging technique etc. Also when you say vac bag, Im assuming youre laying the cloth on your mould, wetting it out and applying a vacuum?
1: single layers will have gaps, and you can see through them. Not all fabrics are created equal (as fiberpro shows)…
2: that last pic looks like you didn’t even vacuum bag it!!! I see the tows are not evenly compacted. If so, um yeah, there is your problem right there.
Too much vacuum, you sucked out too much resin. If you just want to get a single laysr part by wet bagging just place a perf film on it and instead of a non wooven use one layer of peelply to make sure that you will not suck out that mich resin.