Question for any Engineers or Materials Scientists out there

[Flem]

So I've got these materials and was considering doing an experiment, making a unidirectional pretensioned carbon fiber laminate.

I'm thinking of wrapping the carbon fiber with this 1.4oz plain weave fiberglass cloth, making a torsion box construction, which I hope would help stabilize the carbon fibers and hopefully add some elasticity to the matrix.
My issue is that I have no means to do any comparative testing to see how it performs against a fiberglass laminate. The only tool at my disposal is a home made tensiometer I made for lacing up bike wheels.

But since its not calibrated to any know scale, its only a reference tool. Plus to use it I would have to cut it and a fiberglass laminate into 3/8"X 12" sections and still it would only be a comparative exercise.
So my question, is there any body here who has access to lab equipment that could be used to get some meaningful numbers? Otherwise its just a subjective exercise. I know a couple of you out there have alluded to a materials background and if you are willing to do some testing, I would be happy to pay shipping and any other associated costs.

[williwaw]

Flem, your dial indicator looks like it would work fine, maybe by making a few mods on the test fixture?

please describe your proposed layup in a bit more detail.  Dimensions of the torsion box?

[Roy from Pa]

Looking forward to this one..

[Shredd]

Sending you a PM...

[Flem]

Willie, the tensiometer won't give any usable numbers. Its just for making sure of equal tension from one spoke to the next. The laminate I am thinking about making is the same as a fiberglass composite one;
.050 X 1.75" X 72"  I would do a vacuum infusion to minimize excess resin and should be able to get at least a 60/40 fiber to resin ratio. But it's a lot of work for nothing if I can't get it tested and compare it to Gordons or Bearpaw.

[Mad Max]

 
would a guitar tuner work

[williwaw]

for a lam of .050 X 1.75" X 72" , I think the glass cloth will be extra baggage.

you could make form by routing a wide shallow groove in a board, and then sawing/sanding the board away. the torsional box you mentioned is the part I do not visualize well.

what do you want tested? the stiffness of the lam?

[Flem]

for a lam of .050 X 1.75" X 72" , I think the glass cloth will be extra baggage.

you could make form by routing a wide shallow groove in a board, and then sawing/sanding the board away. the torsional box you mentioned is the part I do not visualize well.

what do you want tested? the stiffness of the lam?

Go for it

[Flem]

Sorry Willie, that was rude. My rational for using the glass cloth, which by the way is .002" thick is because carbon lams are typically under fiberglass, I assume because they are brittle, too stiff? In any case the glass fabric would act like a sleeve, encapsulating the carbon roving. Its a typical construction method for some skis and other equipment subject to flex and torsional forces. No form other than a dead smooth, sealed surface need for vacuum infusion. As far as testing goes, I am interested in all the same data that fiberglass lams are tested for.

[williwaw]

Sorry Willie, that was rude.

I thought so too, and was reading
https://www.tradgang.com/tgsmf/index.php?topic=161214.msg2791972#msg2791972
when I saw your most recent post.  Apology accepted.

As far as testing goes, I am interested in all the same data that fiberglass lams are tested for.

testing for stiffness would be the most useful, seeing how bow designs typically don't push the limits for ultimate strength. For the cost of shipping, you could buy something like this
https://www.amazon.com/uxcell-Thickness-0-20mm-Measuring-Silver/dp/B07JB1CV8G/   
if you have a caliper to measure the thickness of your lam, you could probably get by using an arrow spine tester to measure deflection.

Hopefully others can weigh in with other things to test for.

[Flem]

Thats funny, you were digging for some s#!t to sling
Not that I blame you, I deserved it.

[Shredd]

Until we get a chance to talk, here are my thoughts... 

Number one... Unless you are doing something that is unique and different I suggest to go buy some lams... 

Two... I hear nightmares about carbon...  I also hear it only buys you 2 to 4 fps, so if you don't have a maxed out efficient design that's shooting 190+ fps and you want ultimate or record speed I may opt to use carbon, otherwise I don't see the purpose of using it in the working portion of the limb... Now using it to lighten up and stiffen up the last 5 to 6" of limb is a different story...  Trick is how to pull that off... Carbon is brittle and used to make things stiff and non-bending... Glass is tough and handles bending well... I personally think you need to use each material where they are needed most and work the best...

If you op to go through with this...

The tow must be all straight with no twists in it to give you a better quality product... To make all the fibers evenly tensioned will be a challenge and almost impossible at this scale but may not be totally necessary to give you a decent lam...  Using woven glass may not be wise... I has different properties than carbon, especially the fact that it is woven vs the straight fibers of carbon...  You may find that the woven glass may/will turn white when flexed to a certain point because either the glass or resin is fracturing or separating from each other... It may work well in other applications where it is stiff or with very little bend... It may work on the underside of carbon just as the scrim in a glass lam... Or I could be totally wrong and the stiffness of carbon could totally override the properties of the glass and keep it from fracturing...  If you are shooting for a certain thickness I would add an extra .005 to .010" more material to be sanded off to get rid of irregularities on the surface...

[Flem]

No place to buy unidirectional carbon lams. Thats why I am considering this. Personally I'm not that keen on carbon in flexing applications, not its strong suit. But there is an ongoing obsession with carbon and I'm curious if its because of how pretty it looks or if it actually has some performance value in the context of bow making. As far as the glass fabric is concerned, I'm not worried about it failing. The MOE of E-glass is about 25% of carbon and at a total thickness of .004", less than 1/10th of the final laminate thickness, it's basically an Ace bandage for the carbon. I've got a protocol worked out for the lay-up, the spool is on a turn table to preclude twisting and the tow is laid down in one continuous strand to insure even tension. I've been thinking about this for some time and I'm banking on the success I've had with the same protocol making E and S glass unidirectional bow laminates. My working surface is a piece of smooth Formica with 5 coats of release wax, buffed to a mirror finish, no sanding necessary and with the vacuum infusion process the exact thickness is controllable.
This is test, only a test and it might not even happen if I can't find someone with access to lab equipment to verify the result. But I might just do it in any case, just for fun. 

[Flem]

Damn! All the trouble I've gone to keeping my image off the internet and you have to go and find one Roy

[Roy from Pa]

 

[Shredd]

Ok...  Cool...  I would like to see it's own thread and a build on it with lots of pics...   Please... 

   Good Luck...  Enjoy your adventure...

[Longcruise]

Here's uni d Carbon.

https://binghamprojects.com/store/carbon-unidirectional-glass/

[Flem]

Mike, thats a limb core lamination. I'm talking about a back or belly lam.

[Mad Max]

AVCase would be able to help but is quite as a mouse on the forums.
you may find him on a flight bow forum, I think he broke a record this year wif a foot bow.

[Mark R]

Flem I'm not sure of your motivation but if you want a Twill carbon lamb for backing go to Morrison Archery and buy it