Tensile Testing of 3D printed materials!

Hey everyone!

For a class project, I printed a bunch of ASTM standard dog-bone style samples and threw them in an Instron tensile testing machine at UT Dallas.

I tested Inland PLA, Hatchbox ABS, and some NinjaFlex semiflex. The PLA and ABS performed as expected–about 45 MPa ultimate stress each, brittle failure for PLA and semibrittle for ABS. The Semiflex, however, stretched 760% before failing (at 20 or so MPa)! Amazing!

Here’s a picture of the samples (from left to right: ninjaflex, PLA, ABS):

Here’s the ninjaflex a few seconds before it broke:

I am writing a report on these tests, which I’ll post later. It’ll have the details (precise yield strength, loads, elastic moduli, etc). Enjoy!

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Ninjaflex is insanely strong, I have yet to tear any of my ninjaflex prints yet. My ninjaflex printed wallet has been holding up for about a year now.

Yay scientific testing materials!

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It would be interesting to test the inter-layer strength as well

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I will test that someday! I also want to print several infills of different materials to help understand strength as a function of fill density. That will happen later in the summer. :slight_smile:

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You should throw a video up on YouTube if you want a bunch of views :smiley: Thomas Sanladerer would probably like to see it and maybe share with others.

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That is Awesome!

Have you ever thought about a thermal test or know of any that have been done on 3d flexible filaments? I am looking for a strong flexible heat resistant material, possible uses gasket for machine or car, mold for hot wax injection for multiple part replication. Please let me know if you know which material would be best to use for these applications.

Thanks,

Matt

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That’s a tough one… The issue with heat resistant parts is that 3D printers rely on relatively low glass transition and melting temperatures to successfully extrude the material. This material (NinjaFlex semiflex) melts at about 160-180C or so, and begins to soften at 50C. It may work in a car engine, as most are designed to operate at 100F (I think), but there is not much of a factor of safety there and I would not necessarily trust a part to serve its designed function, especially if the engine were to overheat.

There are methods to do tests of materials in controlled temperature environments, but I am not sure if I have access to them. I would certainly like to try, though… Maybe a DIY tensile testing machine is in order. With a 3D printed heated bed and some fiddling, a decently stable temperature can be achieved in an enclosure, and it is also possible to create load cells and a few thousand newtons with screws and stepper motors.

Maybe someday… All that is easier said than done for sure. There’s a reason tensile testing machines aren’t exactly commonplace, much less temperature controller ones.

I’m not sure if you meant F, but 100C would be closer.
In short, car engines are cooled by water, which boils at 100C (212F) (at sea level and some other factors) and therefore tend to hover right in that range. For most modern automobile “operating temperature” is 190F to 250F (88C to 121C).
In longer: because the water used is mixed with other agents which raise its boiling temperature, and generally cooling systems are pressurized, which raises the boiling point further, around 250F (121C) is the max temperature for “everything under the hood”, but there are much hotter spots, e.g. catalytic converters (800F, 425C is not uncommon for their outer skins). In general, I personally count on anything under the hood to be at least 190F during “normal operation”, possibly spiking to around 250F during extreme periods of normalcy. Anything hotter is near a heat source such as the exhaust, or something has malfunctioned; other spots MAY be cooler, but I wouldn’t count on it if it’s in the engine compartment.

I love this post, I have been meaning to do something similar but haven’t had the time. If I donate some bridge nylon , 618 and 645 could you run the test again? Knowing the tensile strength of what your working with comes in handy.

When you stop the vehicle, there can be a fairly brief period where under the hood temps spike as the exhaust manifolds dump heat in a very enclosed area and no air moving through.

This would be a an interesting (or not) experiment to put a few sensors about and see what it does go up to.

And it can go quite higher if you have turbos. There are companies that make equipment that keeps the car and fans going longer to cool things down after you park the car. This keeps the oil from burning in the turbos.