Strength of different filaments

[zumfab 3]

I couldn't help but notice that the carbon filled filament has a pretty disappointing performance. I understand it is supposed to be a little stiffer until it breaks at not a much different point from where normal PLA breaks, but I am not really sure that has been quantified.

 

[pm_dude 27]

Yeah I had the same reaction when testing it myself.

 

[hreedijk 4]

When I get new materials (some day) I will test them. I'd love to do PET.

 

My favorite too!

I've made a crush test on a professional pressure bank to know how much weight a standard printed cylinder can hold, it was a surprising outcome!

I'm not sure if I'm allowed to share the vid and results, I'm willing to ask if anyone is interested, cannot promise anything although....

 

[gr5 2,026]

Can't you share the results *without* the video? Why wouldn't you be able to share the results?

 

[hreedijk 4]

Because I made those tests for a company as a beta tester, I've asked it already, waiting for an answer.

 

[codemaven 0]

Great to see some practical tests being done. I've always been skeptical of the carbon fibre filament myself because by the way it's described I just can't see how it could possibly be stronger than regular PLA. It's just PLA filled with short chopped carbon fibres... That is really no different than Bronzefill or anything like that. What gives carbon fibre products their strength is that the fibres are long and interwoven or intertangled with eachother, which just isn't the case in the PLA. I actually wouldn't be surprised if they weakened it overall because I don't think the PLA will bond 100% to the fibre as it would if it were just homogenous PLA.

Cheers,

Troy.

 

[hreedijk 4]

Good news, have a go to publish some results, here they are:

I've done beta testing for ColorFabb XT colors and have access to a bench press, could not resist to make some pressure tests with it.

One of the tests was a 45 degrees structure like the image below:

The walls are 2mm thick and printed with a layer height of .2mm and all perimeters, no infill.

Purely out of curiosity I wanted to know what kind of weight this structure could handle.

The bench press keeps pressing until is detects that there is no resistance anymore.

In the video below you'll see how that looks:

 

The result was a pressure resistance of 0,570 kN (kiloNewton) = 58 kilograms.

Knowing that I've made a cylinder with a diameter of 75mm, 1.2mm wall's and no infill.

Printed 5 of them in XT black with different temperatures starting at 220 degrees up to 260 degrees.

Main goal was to see what temperature gives the best layer adhesion, horizontal and vertical.

As expected, cylinder 1 and 2 couldn't handle much pressure, the adhesion of the walls was not good and during the test a crack sound was audible what was caused from poor layer adhesion.

Cylinder 3 exploded during the test, at that point no video was made anymore of the black cylinders during safety reasons.

The video of that exploding cylinder can bee seen here:

 

I printed another cilinder in XT transparent, made a safe shield for the camera and myself, and filmed that test also:

 

Gathering all the tests together in one graph:

Calculating newtons to kilograms:

 

 

You are reading it right, ColorFabb XT can hold more than 825 kilograms with a wall thickness of 1.2mm !

Imagine what that would be with a wall thickness of 2 or 3 mm.......

The remains of the test on the bench press:

 

All cylinders collected together:

 

 

[ultiarjan 1,221]

Harold, nice test!

Am I summarizing correct when I say the optimum for strenght is around 250 celcius ?

At what speed did you print the test units ? (higher speed needs higher temp ...)

 

[hreedijk 4]

Thanx Arjan.

Yes, the optimum temp is around 250 degrees, of course this depends on the measurement of the thermistor.

Print speed was 50mm/s for all the cylinders.

I'm going to make the construction below to be able to make more precise measurements for layer adhesion:

 

If anyone has comments on that to improve the design I'm all ears !

 

[calinb 11]

Maybe the community can think of building up a database with result data?

 

Perhaps this would be possible, but from my experience printing Taulman 618 and Oregon brand plain green trimmer line, one would need to control the water content of the filament to obtain meaningful comparative results. I've found very dry 618 (which prints much clearer/less foggy than typical 618 filament) to be much stiffer and harder than a typical 618 print. Fully dried nylon does not emit any visible water vapor from the nozzle--ever, but the translucent and shiny surface reflective quality of the printed part (and improved clarity--even in thick areas) is the main indicator that I use. The filament cannot be left out of a desiccant bag for more than a few hours after drying in order to achieve the stiffest and hardest possible print. Dry filament also improves bed adhesion on my Garolite bed.

 

[solid-print-3d 30]

@calinb,

How do you dry your Nylon?

 

[calinb 11]

@calinb,

How do you dry your Nylon?

 

I remove it from the spool, tie the coil with a fabric tie to keep the ends from popping loose from the coil and touching a heating element, and put it in a convection oven for a few hours. I've used both "normal" heat mode and the convective mode and I don't know whether the convection helps to more evenly burn off the moisture or carry it away, but it doesn't seem to hurt. I put my large desiccant bags in there at the same time.

I try to set the oven temperature just over the boiling point of water to speed things up, but 100 C is well above the glass transition temp for nylon. Any kinks in the nylon can result in a "set" in the filament after it cools so make sure the filament coils are nice and round. Using water for calibration and also a laser thermometer, I've found the dial on my oven (and the laser thermometer) to be fairly accurate.

 

[valcrow 144]

Can't believe I missed this thread great info!

 

[DidierKlein 729]

Thanks for the tests Harold XT is really a great material

 

[hreedijk 4]

Thanx Didier, it is indeed great stuff, more test will follow when I have the time to finish the layer adhesion tool....

 

[DidierKlein 729]

The way it explodes seems pretty dangerous tough but you have a good margin before reaching 800kg of pressure

 

[hreedijk 4]

It is indeed a bit dangerous.

My first thought it would break at the layers, the first 2 cylinders just cracked because of bad layer adhesion.

But the third one had a very good layer adhesion, so well that it just exploded randomly at the cylinder, not at all at the layers, shards shots everywhere.

We took 2 cardboards with a total thickness of 12 mm and made a hole for the camera, just to protect our self.

 

The explosion does indicate that, when you have good layer adhesion, it will make a strong solid part which can handle a lot of weight.

 

[protoplant 0]

Hey everyone, Sorry we are a bit late to the conversation, but we were just informed of this thread.

Very interesting experiment, Gr5! Thank you for sharing your data.

Just to be clear, we don't claim improved strength in using the CFPLA. In order not to clog the nozzles of printers, we use short fibers that we found to give a boost in stiffness, but not strength.

Here is the link to the standard ASTM test methods we used to test stiffness: www.proto-pasta.com/testing-procedures

Our test includes a solid part and standard method which may be more sensitive to the boost in stiffness. This measurement is rate and load dependent, so different conditions could show a different result. I wonder if the test results would be different for a solid (100% infill) bend specimen.

In any case, aside from rigidity, our customers like to use CFPLA for its low shrink/warp for high dimensional stability parts, print characteristics, and aesthetic.

User CodeMaven was 100% correct in that the more "stuff" you put into PLA, the weaker it becomes. So it's always a matter of balance... enough CF to make things interesting and produce some increase in rigidity, but not too much to make the material unusable. We are working within hardware limitations to create interesting and accessible materials, but at the end of the day, a majority of home printers can only handle very basic plastic composites at this point in time.

All of our testing data is made public, and we have an extensive material FAQ on our website which addresses the benefits and limitations of each of our materials, including a discussion on rigidity vs strength. It is never our intention to mislead people, but the clarity of our message is something we continue to improve on.

So, once again, thank you for sharing and for the discussion. Happy printing!

 

[jeremie 13]

Even though the initial tests are really informative, I have to agree with protopasta. The most useful characteristics of CFPLA imho is the weight/stiffness ratio. It is just incredible compared to all the others I could try: even more, you can get a much stiffer object with thinner walls. In this regard it would have been fair to weight also the CFPL part, which is the only data missing in the review.

This is why CFPLA shines for R/C models, at least where heat is not an issue (still, I used it as holders for the motors of a 2KG drone, 50% infill -- I then switched these parts to black XT for production for more safety, all the rest is CFPLA).

The second outstanding property of CFPLA is its beautiful matte finish (irrelevant in the initial testing).

The drawbacks are: price and the fact it is still PLA, with a low melting point.

It would have been terrific to have a CFABS instead or even better a CFXT (mix brands! Protopasta: I think colorfabb sells pellets... why not give it a try?)

Just be careful at the design and slicing phase, as the carbon fibers reinforces the part mostly in the horizontal plane. It is still subject to delamination.

 

[aviphysics 9]

I think I would add a "hot car" test. Maybe using a rig like the bend test and subjecting them to a heated box for 8 hours at the temperature of a car interior on a hot California day. I would say without load, but not totally sure.

The point would be to test what materials will hold up if you leave them in your car on a hot day.

Afterwards, the pieces could be subjected to the bend test, to see if they held up.

 

[ultiman 0]

Hi!

Nice test, I was looking for something like this. However, one important detail is ignored: Printing orientation of test pieces. Some materials (especially ABS) tend to be much much weaker in Z-direction than in XY-plane. Therefore it may make huge difference if you print the test bar in horizontal or in vertical position.

Now that you're already experienced with these tests, I encourage you to perform comparison tests with items (of same or different material) that are printed in horizontal vs. vertical position. It would be very interesting to see the results...

 

[gr5 2,026]

I printed the materials in an orientation that I thought would be strongest. So the "band" or loop part doesn't care much about layer adhesion. The rectangular part where I tested the flex/bend - that part has more forces and one of the parts broke along a layer line due to not quite perfect layer adhesion (although pretty good!). I think it was the ABS part.

I am aware that ABS can have layer adhesion problems (actually everything but PLA has these issues as they solidify almost instantly when printed). I've had problems with this in the past - both ABS and Nylon.

 

[tinydancer 0]

This is such a great thread, thanks to all who contributed to the testing!

 

[ultiman 0]

I printed the materials in an orientation that I thought would be strongest.

 

I see. Actually, that's my point. I guess PLA would perform much better against other materials when the weakest orientation would be chosen.

You can't always choose the optimal orientation for your print (forces may be multi-directional or some other reason may prefer printing direction which is not optimal for strength). So, knowing the properties of materials from suboptimal printing direction would offer even better judgement for selecting the material.

 

[aviphysics 9]

What about some sort of flexture hinge test (number of flexes of a certain angle before failure) and a self abrasion test (i.e. measured wear on two parts of the same material rubbing against eachother.)? I suspect we would see a real difference between materials on those areas.