Layering various cloth weights for added strength?

General Discussion
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Basic test program starting!

4oz plain weave E and S glass samples being laid-up with epoxy, polyester and a bio resin (sugar product). All will be vac bagged, infusion not possible with the bio resin as it is SO viscous.

Initially simple tensile and flex tests will be done in 0/90/45 directions. There are so many tests that could be done as shown on this thread, and would be interesting, but one has to start somewhere.

Keep the suggestions comming.

“Industry” over here a little slow in responding so if anyone has materials they want testing and can be bothered to send them over please do so, PM me for an address.

Just to make you think how’s this…

A uni-carbon sample we made for the chainplates of a racing yacht measured 50mm wide by .75mm thick broke at a tensile load of 2580kg…As a wooden boatbuilder I do love composites!

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Ooouu… this is exciting.

Quick calculation and some questions before I head off and hurt some nails.

You’ve referred to 2580 kg as a force, can I assume that 2580 kg actually means 2580x9.81 newtons (N) or 25.31 kN? If so then the breaking stress would be

675 MN/mm (97902 psi)? Which is good stuff for a composite. carbon/resin 350-1050 MN/mm, glass/resin same ballpark.

Questions:

Can you pick off a working Young’s modulus during the test?

Can you pick off strain during the test?

Can you get a density (so we can do strength/weight comparisons)?

Would you describe the preparation of samples (pre-stressed or not)?

And of course, even knowing that I’ve already asked too much, is there any way you can post a plot? If not post, offer one up as an attachment? Its not critical, just something a geek would want to see. (Actually I want to play with the numbers, strain energy calculations and stuff. I don’t expect anything new, but more to just put the whole thing in context with theory.)

I will start to contact suppliers. As I do I will post those suppliers I’ve contacted (and the outcome) on this thread, so as to prevent duplication. I’m assuming others might want to see a little testing too.

Like I said, ‘ooooouuu’ … but please add a ‘weeee’ to that. This looks like it might be fun. Thanks!

kc

Unit Conversion/Prefix Notes:

1 N/m*m = 0.00014504 psi

1 psi = 6 894.76 N/mm = 6894.76 Pa = 144 lb/ftft

1 MN = 1 000 000 N

1 kN = 1 000 N

1 kip = 1 000 lb

1 inch = 2.54 cm = 25.4 mm = 0.0254 m

1 atmosphere (atm) = 14.7 psi = 101.3 kPa

e.g. 97 902 psi = 6 660 atm

It gets better, consider…

1 psi = 144 lb/ft*ft

e.g. The pressure generated by having someone who weighs 144 lb stand on tile 12 inches by 12 inches. So 97 902 psi is mind boggling -it’s 14 097 888 lb/ft*ft. It’s like having every one in a modest size town stand on each others shoulders, the (poor) bottom guy standing on a tile 12 inches square. (And that’s assuming he could somehow manage to distribute the load over the 12 square inches.) So why do surfboards break again? (That’s a rhetorical question, but what the heck, take a shot at it if you like.)

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Questions:

Can you pick off a working Young’s modulus during the test?

Yes

Can you pick off strain during the test?

No, may extensometer committed suicide, awaiting new one.

Can you get a density (so we can do strength/weight comparisons)?

Definitely.

Would you describe the preparation of samples (pre-stressed or not)?

Materials will be laid up on a glass plate and vac bagged, no pre-stress except those resulting from contraction on cure.

And of course, even knowing that I’ve already asked too much, is there any way you can post a plot?

The machine automatically generates a plot. I’m sure I can post them somehow, maybe have to scan them.

Attached an excel sheet of some tests I did for a longboard layup. Hope its of interest…