This shows the effect better - http://www.fibermax.eu/shop/images/4.JPG
you don’t happen to have the force vs displacemnt graphs for these samples do you? I’d love to take a look at them to compare the stiffnesses. i’d also love to know the cross sectional dimensions.
I’m currently doing the same type of testing but with unidirectional, 2x2, and a mixture of both trying to find theb est resistance to bending without using a core. I’m also playing around with adding sleeving material in both carbon and kevlar materials.
I should start testing within the next week, and i’ll be happy to post up my results as well.
Please do, post up any photos or findings…
Yes, I have the graphs for each test. But that’s why I put the force and displacement values on the images.
As for max stiffness, unidirectional carbon in the orientation of the load will get you the best result.
yeah, we have several samples of unidirectional that we will be testing. the sleeving is there to try and deter delamination between layers and to resist any torsional forces our prototype piece (not the test samples) may incur.
will you be doing a 3 point bend test similar to TET or different?
yes, 3 point bend testing.
Is there a standard material sample length and width when doing 3 point tests for composite materials?
Awesome, is there a reason why you are not doing it with epoxy? I thought that was the strongest combination.
ASTM D 790 - 03
ASTM D 6272 - 02 for 4pt. bend
it mostly all depends on thickness, which changes the W and L sizes. Also, sometimes depends on fiber ori, but not always.
There’s no reason, this is simply what we were testing at the time for a specific project. Just trying to show the customer the relative strengths of the different construction options, no trying to achieve the highest ultimate strength.
we got our first set of testing done today. I’ll hopefully be able to post up some pictures and test results early next week.
on a similar note, TET, do you have a good source that shows good examples for failure modes in composites. We have a few samples that all look ever so slightly different at the failure point, and I want to make sure I document to correct mod of failure whether it be delaminatation, buckling, etc…I’m quite new to composites and don’t want to be wrong about the mode of failure when analizing the samples.
PM me next week, I’ll see if I can find the correct ASTM standard, and if they have pics of failure modes.
Could I get a copy of those failure modes as well if you find them Riff?
It depends on the type of testing. Tensile, compression, and bending failures will all be different.
well we are doing a 3 point test, so I’ll only need bending failures.
riff, I think I saw that spec at some point when first doing research on composite testing, but I have no idea which one it is now.
ASTM D 790 - 03 for 3 point bend
ASTM D 6272 - 02 for 4pt. bend
that’s the spec (D790) we “followed” (as close as we could), and I don’t believe it has modes of failure in it. Maybe I don’t have the full spec, but i think it’s just test set-up and result caclulations. I’ll have to look it over again.
Aloha Tet ,
What core were you using? What do you think caused the failure?
Bobhexa
Hey there,
could you please share your test lab contact info? I would like to have them test a few pieces as well. What size do they need to be?
Thank you,
JoR