Stength of US compsites Epoxy & 5.7 oz

[cookerq62]

For one of my classes we had to build part of a go-kart frame. The material we chose was carbon fiber. So I went ahead & ordered some 5.7 oz plain weave carbon from us composites & used some left over resin from one of my builds to lay it up. When we were done I had some left over so I made some samples to put in our test machine. I threw some scrap strips on wax paper & let them cure for about 20 hours & then stuck 'em in the test machine. Over all I broke 16 samples that had an average break strength of 44,000psi. The samples were all over the map from 30,000 psi to 73,000 psi. I expected that because the samples looked like a monkey layed them up. The really cool thing about the carbon is it doesn't behave like a metal at all. There is zero plastic deformation right up to when it breaks giving it working strength better than mild steel. So basically if any reinforcements you do or parts you build using the resin & carbon USComposites sells are going to be stronger than mild steel no matter how bad of a job you did. All of the pieces broke as a result the crimp in the fabric. Crimp is essentially an internal shear that results in the fabric due to it's weave. The effects of this are less pronounced in twill fabrics and nearly non existent in stitched & unidirectional fabrics. So those fabrics will be stronger. I attached a pic of one one of our samples under an electron microscope after it broke. You can easily make out the carbon & the epoxy. I hope some one else finds this stuff as interesting as I did.

 

[Motorheads5]

That's cool Thank's for sharing, WOW 44,000 psi That's impressive.

 

[onesojourner]

very cool.

 

[aussiemat]

very interesting you wouldn't have any numbers on plain fiberglass to compare would you.

Cheers
Matty

 

[yamaslut]

good stuff, thanks for posting that.

 

[shawn_NJ]

Really cool. I would love to see the results if you bagged the samples. Did you get to use varying layers?

 

[Mark Gomez]

hell yeah thats good to know I used that exact Carbon on my ski when i reinforced it again. The stuff looks great too, been a few months, some gnarly conditions and the carbon still looks show room quality, no blurring like cheaper carbons.

 

[WAB]

Nice post. I'd also like to a the comparison with regular S glass cloth.

I really like the US comp 'house' brand of epoxy. It's really cheap and easy to work with.

 

[cookerq62]

Really cool. I would love to see the results if you bagged the samples. Did you get to use varying layers?

I basically took strips and folded them back & forth on them selves which came out to about 4 -5 layers. The weave was all over the place & so was the thickness, plus the resin wasn't fully cured. With a controlled layup 60,000 psi shouldn't be a problem. Most of the better looking pieces were already there. The pieces with globs of resin in were the weak ones. I wish I had access to these kinds of machines all of the time so I test more stuff like fillers, glass & Kevlar.

 

[shawn_NJ]

I basically took strips and folded them back & forth on them selves which came out to about 4 -5 layers. The weave was all over the place & so was the thickness, plus the resin wasn't fully cured. With a controlled layup 60,000 psi shouldn't be a problem. Most of the better looking pieces were already there. The pieces with globs of resin in were the weak ones. I wish I had access to these kinds of machines all of the time so I test more stuff like fillers, glass & Kevlar.

Great info. I was doing some panel testing a few months back. I was playing around with standard weave 5oz kevlar. If you pay attention to the weave and lay up 2 layers +-45deg, and 2 layers +-90deg, with one layer of 9oz sglass (sglass @ 45/45) on the top and bottom.....then vac it down....its absolutly amazing how strong the piece comes out.

 

[cookerq62]

One of the coolest things about the stuff is being able orient the strands in the direction of your load to get maximum reinforcement. We used just the tow to reinforce most of what we did. It ended up looking kind of like one of the composite air cylinders.