Laminate Sample #29: Thin Open Molded Chopped Strand Mat / Polyester Resin

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This laminate sample is about chopped strand mat and how it isn't very strong but has some interesting properties. The sample is very simple - just two plies of 3/4oz (in the US we call mat by weight per square foot - so 6.75oz per yard or about 180g per square meter) mat open-molded with GP polyester resin. Plenty of rolling but no vacuum bag or anything fancy here.
There is a discussion of representative volume elements / unit cell of a lamina and how that really only works when each lamina has fiber pointing an a measurable direction. With chopped strand mat, its more of an all-the-directions thing giving a quasi-isotropic (in-plane isotropic) laminate from even one ply. Fiber volume fraction and the idea of a unit cell is used to estimate laminate properties using the rule of mixtures concept to volume-weight properties of the fiber and the resin matrix.
At the end of the video this sample is compared to #17 (glass/epoxy) and #27 (carbon / epoxy) and you can see just how much of the stiffness of this one comes from thickness. That thickness is mostly resin - and it's heavy - nearly twice the weight of the other samples!
Check out the EC! website for dozens of articles about building with composites - and lots more laminate samples:
explorecomposites.com

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Опубликовано:

2 июл 2024

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Комментарии : 17

@GrantOakes 3 года назад

I'm surprised to see 2 plies of 3/4oz mat being that thick! When I was manufacturing carpet cleaning machines we used 4 plies of 1-1/2oz mat and it was exactly 1/8" thick for the main part of the housing and we added 3 additional plies in the area of the vacuum tank (with a urethane foam stiffening rib) that ended up being 1/4" because of the resin barrier. We used a short nap paint roller to wet out our laminate and the recovery tank portion was so strong that it could stop a .38 caliber bullet at 25 yards!

@ExploreComposites 3 года назад

Yeah it surprised me too... but I wasn't shy about adding resin laying it up so I have no doubt it could be thinner! I'm an epoxy guy so this mat and poly stuff keeps me guessing. Smells bad though. Your laminates for the carpet machines sound very well compacted - that's an impressive thickness for four plies of 1.5oz. Don't doubt it can be done with a good laminator on the roller! Was the .38 at 25 yards a standard QC procedure?

@GrantOakes 3 года назад

@@ExploreComposites I got a call from a customer who accidentally pushed his machine down a flight of stairs, expecting it to be destroyed. Only a rocker switch was damaged and he told me my machines were "bullet proof". That got me thinking, so I took a sample of the laminate from the recovery tank out to a field and shot it with a .38 caliber hand gun and it did leave quite a mark along with some de-lamination, but had it been the actual machine with water in it there would not have been a leak. Right after that my advertising had a caption of "Bullet Proof!"

@mikexhotmail Год назад

You are the best my man.

@hollandsd123 3 года назад

Is your spreadsheet available to the general public to use? Mainly the template rather than the full library?

@ExploreComposites 3 года назад

I could share it - not really much to it. The plan is to make full pages for each sample with the spreadsheet there but I haven't got to it yet. I'd share the huge one but it's so messy and has so many scratch-pad notes off to the side that it'd just be confusing. Email me from the EC! site and I'll send you a clean copy if you want. chris@explorecomposites.com

@flyingrugman 11 месяцев назад

can this fiberglass mat sheet be used as a core? if possible, I want to try it by coloring it black so the color blends better with the carbon.

@ExploreComposites 10 месяцев назад

It could, but it is a heavy way to build thickness. There are carbon chopped mats available - often recycled - that might be better. Also check out the gray Lantor Soric that is an infusion core that blends nicely with carbon visually.

@flyingrugman 10 месяцев назад

@@ExploreComposites thank you for the reply, very appreciated!

@fullsendmarinedarwin7244 2 года назад

What if you vacuum bag the hand layup wouldn't that be a lot better resin to fiber ratio? More like 60/40

@ExploreComposites 2 года назад

Yes. Several samples here are made this way. Chopped strand mat and polyester aren’t the best choice though.

@fullsendmarinedarwin7244 2 года назад

@@ExploreComposites thanks for reply. Love your example videos I ended up binge watching most of them. Given me some good ideas on some methods and materials I want to try. I'm currently building my first plug / mold

@willhull9677 3 года назад

so would you say a gallon is enough to do 5 yards of mat?

@ExploreComposites 2 года назад

Probably - if its 200-300g or 3/4oz mat... but just.

@user-zx5kw9bd1c 3 года назад

OK :-)

@dogodogo5891 Год назад

hi i planned to make some flexible clear sheet like yours its should be transparent as possible because sheet will act as sort of lens, there are some pre-determined grit on the master mold iam thinking about fiberglass+ clear polyester because it's cheapest my question are what mat(chopped, tissue, woven) should i choose that will give me most clarity?

@ExploreComposites Год назад

I am no expert here so this may not be helpful at all, but my understanding is that a fine woven s-glass would be the most optically clear, though a fine e-glass woven would probably be similar. You want minimal fiber bundles. Maybe a few plies of a light glass veil or remay would work too. And there are clear resins used for wood coating, bar tops or surf boards that are very close to clear. Generally I'd go for smallest fibers in smallest bundles - but as a lens, fiberglass may not be a good option. Worth a try though - I've just never seen anybody use it this way before. Have seen fiberglass attempts as windows in boats and it wasn't ideal!