Jul 14, 2010 at 7:11 pm #1261173
And so it begins…
Jul 14, 2010 at 7:16 pm #1629032
It is still very early days but for anyone interested in the details, this is 0.33 oz/yd² Cuben fiber from Quest Outfitters. The strip you see in the tensometer jaws is precisely 1 inch wide and the whiter area in the center is a 1 inch by 1 inch overlap bonded with 45 milligrams (yes 0.045 grams) of our solvented moisture-cured polyurethane. The strip broke at 17 pounds force and the bond was totally unaffected. I'll experiment over the weekend with progressively smaller bond areas until the bond becomes the failure point. I'll also do peel adhesion tests, this is tensile shear adhesion.Jul 14, 2010 at 7:56 pm #1629041
@climber72Locale: At my desk
The geek in me just giggled! Very cool idea, can't wait to see the data!Jul 14, 2010 at 8:08 pm #1629051
This is absolutely amazing. I can't wait to see all the results!
If I read the cuben fiber spec sheet properly, a 1" strip of the 0.33 cuben should break at 35 lbs. Correct? So with the overlap bond, it is currently breaking at about 50% of the spec. Any chance you can test a piece without a bonded area just to see what it will break at?
I (and probably many others) will be following this thread closely. A big thanks in advance for posting this type of info for the community to learn from.Jul 14, 2010 at 8:12 pm #1629054
Hey Steve, I was hoping you would join in on this thread, glad to see you here already. I tested 5 strips without a bond and all broke at 15-18 pounds force. The alignment in the tensometer jaws was perfect and the failure mode was a sudden catastrophic failure rather than a progressive tear which would indicate poor alignment. A representative picture of the failure mode is below.
Close Up of Failure
Besides, any strip which fails at a spot other than the bond might as well be non-bonded for purposes of characterizing the Cuben fiber itself right?Jul 14, 2010 at 9:08 pm #1629075
Sam FarringtonBPL Member
@scfhomeLocale: Chocorua NH, USA
Could you try some strips of other fly fabrics, like TH silnylon and spintex, for purposes of comparison?
SamJul 14, 2010 at 9:19 pm #1629080
. .BPL Member
@biointegraLocale: Puget Sound
This is fantastic. Thanks for sharing with the community. I am looking forward to seeing the data and would be happy to send you some test swaths of varying weights of cuben scraps and would encourage anyone else to do the same in order to get a more accurate scope of figures from multiple random batches. Depending on the size required, I may have some well used material to supply for comparison, if it would be of any interest to you. Judging by the photograph, the 1" strip looks to be approximately 12" in length, including what is presumably well in the clamp. Am I close?
Did you perchance weigh the fabric samples in order to see if they were true to spec?
Thanks for posting photos as well!Jul 14, 2010 at 10:33 pm #1629107
Scott Van DoeselaarBPL Member
@vandoeLocale: Southern CA
Very nice. It is great to see quantifiable results.
You mentioned "our" polyurethane. Can you shed any more light on this bond material and its characteristics?Jul 15, 2010 at 1:03 am #1629152
@rcaffinLocale: Wollemi & Kosciusko NPs, Europe
Interesting (or curious) that the specimens did not fail at the edge of the clamp.
CheersJul 15, 2010 at 1:04 am #1629153
Sam and Aaron: If anyone would like me to get the true mass and tensile strength of other fabrics, I'm perfectly willing to do so.
Aaron: You are incredibly close, the samples I was cutting were 12.5"x1" by in truth I'll probably switch to 6" long samples since this is still plenty long. And yes, the fabric was first weighed to the nearest milligram to establish its true weight.
Scott: I'm not quite ready to disclose which adhesives I'm using but suffice it to say that Loctite is one of our low-cost (and extremely low performance) competitors. Our materials are more expensive but typically much higher performance as compared to Hysol and other commodity epoxies.
Roger: Japenese indeed, it is a Shimadzu 10,000N rig. The jaws are 100% American designed and fabricated though.Jul 15, 2010 at 1:59 am #1629160
@derekoakLocale: North of England
this is a high tech and hopefully more accurate trial of cuben than my basic attempt with rope, cramps and a bucket of sand attempting to do the same thing. My results are not too far out of line with yours. However all of my failures were at the edge of the clamped area, the edge of the glued area, or failure of the glue bond itself. Were your failures elswhere?
Your results are not anywhere near the cubic tech figures. I Wonder how they get such high results? Maybe the forces in my setup were more in line than I thought.Jul 15, 2010 at 3:45 am #1629169
So far all failures have been in the middle of the fabric itself perhaps an inch below the bottom of the top jaw. To me this means that was the weakest line in the strip of fabric under test and the tensometer jaws are not stressing the fabric. Keep in mind that these machines are quite expensive and for precisely this purpose so this result doesn't surprise me at all. Why would the fabric fail at the edge of the jaw/clamp unless that area of the test setup is concentrating force? Sure once or twice that might honestly be the weakest spot of the fabric but surely not every time.
The two epoxies that I wanted to try have been curing for 24 hours so they'll get tested today too when I get in to work. I expect that each of them will add more weight than did the MCU and I would be shocked if either failed in the bonded area. We'll know soon enough.Jul 15, 2010 at 5:11 am #1629178
Kevin BeedenBPL Member
> Interesting (or curious) that the specimens did not fail at the edge of the clamp.
Most tensile test specimens have widened ends and taper down to the actual test area, so I was expecting a doubled-thickness or something at the jaws. But if the samples aren't failing at the jaws, then it sounds like the methodology is fine, and the jaws aren't having any effect.
I'd guess that the failure is due to microtears in the fabric along the edge, as a consequence of the strip cutting process. One might expect this to cause a propagating failure, but it may be that the rip occurs so suddenly that the propagation isn't visible to the naked eye.
Good to hear that the bonds hold up well. I guess a peel test is next…?Jul 15, 2010 at 5:44 am #1629187
Very interesting, but…
“I'm not quite ready to disclose which adhesives I'm using…”
If you don't tell us what adhesive you used or it isn't available to us (MYOGers), then what’s the point of the experiment?
CheersJul 15, 2010 at 10:15 am #1629281
…Jul 15, 2010 at 10:44 am #1629293
Dan DurstonBPL Member
What would make one adhesive better than another, if both are strong enough that failure doesn't occur at the bond? I don't understand the criteria for what makes a high vs. low performance adhesive.Jul 15, 2010 at 11:09 am #1629301
Well said Dan.
I have no problem if Hysol is in fact low performing, I'd just like to see why/how it is. Maybe the peel testing will show a significant difference…just guessing.Jul 15, 2010 at 11:33 am #1629308
Kevin BeedenBPL Member
> If you don't tell us what adhesive you used or it isn't available to us (MYOGers), then what’s the point of the experiment?
To show progress in the development/testing of an adhesive suitable for Cuben? From Chris' comments about competitors, it's pretty clear he works in such a field.
Whilst I guess I'm used to manufacturers downplaying their competitor's products, I'd like to think that we can keep that sort of stuff out of a MYOG section, and echo Steve's comment that such adverse comments should be backed up with test results, or not made; after all, we don't generally care who we buy our materials from, just that they work.Jul 15, 2010 at 11:34 am #1629310
The adhesives that I'm using are available anywhere in the world though not through retail channels. Only from Distributors. The reason I've not posted information on the adhesives I'm using is because I'm not sure they're better for this task, I'm very sure they're more expensive, and I have only just started to characterize our products in this application. But for those who just can't wait, I've gotten the best results with Belzona 2911 (Elastomer QD Conditioner). Solvent appears to be an important component with cuben though. The non-solvented expoxies didn't perform nearly as well as did the solvented MCU (the 2911).
Steve, I wasn't bashing Loctite (or at least didn't mean to) only saying that I might be able to get more adhesion per weight.Jul 15, 2010 at 2:59 pm #1629372
Aha! I knew it was Belzona. I did a little digging and your name popped up along with that company. :)
As for Hysol, as of right now AFAIK, there is not a better way for the MYOG'er to bond cuben fiber. My experience with it has been great. It's readily available, affordable, no bond failures, requires no training (ie. anyone can do it), needs only a brush…I could go on. One of the only downfalls to it is that it is a bit of a pain to apply it especially on the longer sections.
So, I just wanted to make sure that if we are going to categorize the Hysol as low performance, that we come up with something better and share it with the community.
By now most of you guys know I'm a full on nerd and love this type of stuff so I really appreciate the time you're putting in. I'm very interested in the project and this thread has the potential of containing great information for people to lean from.
I'm taking off for the weekend but I'll catch up with you guys when I get back. Good luck on the tests.Jul 15, 2010 at 3:09 pm #1629377
@rcaffinLocale: Wollemi & Kosciusko NPs, Europe
It would be wonderful to test some of the double-sided tapes as well, like the 3M9485PC which is widely used in the yachting world.
In fact, would you care to contact me (email below) about this work – it could become a very interesting full technical article.
firstname.lastname@example.orgJul 15, 2010 at 11:41 pm #1629523
"It would be wonderful to test some of the double-sided tapes as well, like the 3M9485PC which is widely used in the yachting world."
It would be interesting to test some of the “heavier” cuben versions (i.e. CT2K.08 and CT5K.18). Also, the test could be done applying the forces in several directions, not just along the warp.Jul 16, 2010 at 12:07 am #1629527
In addition to a full technical article, the results of these tests should be published in the BPL Wiki (as Derek Goffin did). Otherwise, in a few days/weeks they get buried in old threads.
CheersJul 17, 2010 at 8:51 am #1629847
I'm experimenting with various test speeds and load cell settings in an effort to try to get results closer to what Cubic Tech claims. I just got a result of 25.4 pounds force from a one inch strip which is 73% of the manufacturer's claim.Jul 17, 2010 at 9:39 am #1629860
@geistLocale: Smoky Mountains
I wonder if you would get closer to CubicTech's numbers
if you removed the effects of micro-tears at the edges
by taking the 1 inch strip and folding/gluing the edges over.
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