Triaxial mat wetout

[jimrudholm]

I am running some test samples of a single layer of 30 oz. triaxial mat using Aeromarine epoxy. The triaxial is 50% 0, 25% 45 deg and 25% -45 deg and stitched. The 50% rovings are hard to saturate with a roller and squeege. The part, a top hat section 1" tall and with 1" diagonals and 1" flanges, is made using a section of metal roofing for a mold. Its vacuum bagged on a UHMW covered table and 4-mil plastic film for the bag. Vacuum is 18-20". There are excessive air bubbles along the rovings, the bias layers are saturated.
Any suggestions to get the air out?

[Landlubber]

sounds like you have done a good setup job, how cold was the resin?

[jimrudholm]

Shop temperature in the afternoon was in the high 70s.

[Jimbo1490]

How long between mixing and application?

Their web page shows a viscosity spec of 600 CPS (which I assumed to be rated at ISO Std temp of 25C or 77F) which should have been plenty thin to wet out even triax. The spec sheet also says the work life is 30 minutes @ 70F. Work life *usually* means time for a 100 gram approximately cuboid mass to double in viscosity @ ISO Std. I can't be sure if that's what their spec means since they seem to 'mix 'n' match' some of the spec parameters like temperature. A much bigger mass left in a small container rather than spread out would be expected to get warm and start curing pretty quickly. A warm mass will thin out considerably while warm, but then it may immediately cool and thicken upon application to the work surface, reducing wet-out. Work life can be a misleading spec (if you let it be so ) since cure times aren't linear once exotherm hits. So while it may take 30 minutes to double in viscosity, and doubling from 600 to 1200 CPS still leaves you with a reasonably workable viscosity, in the next 5 minutes the viscosity may go up 10X, leaving a rather UNworkable 12,000 CPS I don't know if this is what's going on with your layup, just offering some possibilities.

Jimbo

[Herman]

Are the roving bundles not saturated, or are they spaced apart a bit, and is the space between the bundles not filled with resin?

How did the stuff look when you were ready laminating?

Are you absolutely certain that none of these fabrics are using using styrene soluble binders? We're starting to see Chinese product that mixes epoxy compatible and non-epoxy compatibles.

[AndrewK]

Sounds like the air is between the 0 fibers? did you use a breather fabric?

Recently I also had the same problem as fg1, I got some what I thought would be very nice +45/90/-45 560gsm weft triaxial tape unfortunately the 90 fibers do not impregnate completely and I returned the unopened rolls. The supplier tels me that the sizing is compatible with epoxy, so I got them to test it them selves and they confirmed the problem. But they are still selling it.

[SamSam]

The corners on the metal roofing mold may be too sharp for that heavy of a lamination even with a vacuum bag. If you are vacuum bagging by wetting out the laminate on the mold and then putting on the plastic and then applying vacuum, that won't eliminate bubbles, it will just make them smaller. You have a better chance of eliminating bubbles by infusing, that is, setting up the whole bag system dry, applying the vacuum and then sucking the resin in one or a few places while sucking the air out in others. Like using a straw.

[GG]

Hey guy does the woven roving have a binder ( chop ) back and if so it is not compatible with epoxy and to tell you the truth i have seen binders tear away from the fabric on new boats even though though they ( S2 YACHTS) were told using a chop back fabric like 1708 would be fine in there build and compatible for use with epoxy ......... Not and to tell you the truth i have seen this problem happen at more then one Boat Co . who went to an all epoxy build in years past .