Weight of fiber glass

[jfblouin]

For example, I assume a projet that need 100 Kg of fiber and with a ratio 33% fibers I also need 200 Kg of polyester resin.

The total weight will be 300 Kg at laminate time.

But what will be the weight after curing and styrene evaporation??

[Raggi_Thor]

Not much less :-)
I think the evaporation is so small that you can disregard it.

[Herman]

I have done some testing with that. For your purposes, you can disregard weight loss due to evaporation. It's in the 1% range.

[rxcomposite]

Evaporation would be the least of your problem. Different glass have different glass to resin ratio. You may be able to wet the glass with more resin but it will not add strength, only weight. You may use less resin content but you get a laminate that is resin starved and cause delamination problem. the industry standard is (with a little variation from other countries):

Glass Glass content
Veil cloth 5%
CSM300 30%
CSM450 33%
Woven Roving 50%

You will need a spreadsheet for that as your laminate schedules become more complex.

[Dutch Peter]

Here's some more info:

Resin infusion and resin content
Resin infusion
how much resin?

[rxcomposite]

Peter,

Thanks. I visited the thread and was surprised at the variations.

True. I myself have used prepregs, vacuum bagged and high temperature cured. Resin content was at 38%. But the guy who designed the laminate was using FEA program.

My data was from a hand lay up contact mold use common for boatbuilders. Still most of the guys in the shop could not maintain the ratio. Only the most experienced guys can do it with consistency.

The more sophisticated laminate design program you have, the more you can dial in the glass ratio, fiber orientation, type of glass (or kevlar or carbon, ect) and thickness.

Rx

[Dutch Peter]

Rx,

Glad to be of help. Guess with what your telling that's just the reason that Class Societies are a bit conservative!

Regards,

[rxcomposite]

Dutch Peter,

Class Societies are always conservative because they are the ones who pay when it breaks. Hahaha.

Rx

[newo eloc]

I was qouted by the supplier 1/3 fibre 2/3 poly resin on duo matt which is a complex w/roven with a ch/strand backing .In a trial run where I measured and weighed everything it turned out exactly 50/50. How can I price a 60 m2 job on that ,live and learn I suppose. How can I get a more even spread of resin if i'm not vac/baging and what is "pre preg" I'll appreciate your advice.

[marshmat]

prepreg = pre-impregnated, meaning a cloth that has activated resin put into the cloth as it is woven, at exactly the correct ratio. It is stored frozen and parts are cured by autoclave.

Getting an even and correct distribution of resin is simply a matter of practice. Lots and lots of practice. Vac-bag helps a lot with getting excess resin out and keeping the laminate tight and in the proper shape as it cures; if you can afford it, it's definitely helpful.

[rxcomposite]

You should know the weight of the mat and the rovings in the complex glass material you have. You cannot lump it together.

Anyway, i think you are just about right. I would guess what you have is a very thin mat on double layer rovings. The mat is there to promote good bonding between rovings. Say Mat, Roving, Mat, Roving, ect. Or Roving+roving,Mat, Roving+roving,Mat. Everytime you lay up, the mat side should face the already laminated roving side.

As a guide, break it down and you shoud get,

30% glass on CSM 300g/m2 or lighter
33% glass on CSM 450g/m2 or heavier
50% glass on Rovings as a rule
53 to 55% glass on Rovings with good packing density.

Marshmat is correct. Practice, practice, practice. Always use a measuring cup and proportion the resin accordingly. Sounds like an overkill but even small shops retain the discipline.