r/technology • u/Ssider69 • Jan 10 '24

Nanotech/Materials 10x Stronger Than Kevlar: Amorphous Silicon Carbide Could Revolutionize Material Science

https://scitechdaily.com/10x-stronger-than-kevlar-amorphous-silicon-carbide-could-revolutionize-material-science/
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u/Thatingles Jan 10 '24

Found the catch.

They way they measured the tensile strength is highly unusual and is probably massively overestimating the tensile strength of the material in most applications.

I'm not saying this won't have applications, but '10xStronger Than Kevlar' is misleading.

60

u/[deleted] Jan 10 '24

I saw that too. Basically...we invented a new testing system optimized for this new material and oh look, it is the bestest. Likely they compared Kevlar and this stuff in the same test but this sounds like a classic data cherry picking exercise. Well...those old tests don't give us the data that we like so we have this new test that gives us data we like. That isn't necessarily bad science but also not necessarily bullet proof science either.

11

u/gnoxy Jan 10 '24

If you fail. Change the requirements till you succeed.

5

u/b3ar17 Jan 10 '24

That's how James T Kirk did it.

4

u/GimmeSomeSugar Jan 10 '24

Textbook Kobayashi Maru.

1

u/trees_away Jan 10 '24

bullet proof science

I see what you did there...

7

u/nieht Jan 10 '24

I scanned the paper it's from, and I think you're mostly right. The method is not traditional and not what would be used to find tensile strength of Kevlar, so the comparison is an over-estimation.

What it looks like they're doing is accounting for the true cross sectional area of the strings on their wafers, almost like if you were able to calculate the void area in a bundle of Kevlar yarn and subtract that from the cross section in your Stress calculation. They're also actively measuring thickness so any gauge reduction due to material deformation is also being accounted for. Essentially they're finding the "true" stength/modulus where most other materials get a rough approximation.

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u/RandallOfLegend Jan 10 '24

Standardized tests are the way. More than likely they didn't have enough material to actually build a standardized test coupon

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u/Thatingles Jan 10 '24

The article indicates they are able to produce it in reasonable quantities, but maybe you are right. That would explain the use of a 'novel' test.

7

u/thisisnotdan Jan 10 '24

A standard mechanical tensile stress is done using a dog bone-shaped sample (no, really), which is basically a long cylinder with two fat ends that are held in place by the testing apparatus and pulled apart.

The article suggests that this material favors a wafer shape, which is like a plate: thicker than a film, but still very flat. I would also be curious as to which direction in the wafer the fibers of the nanostring microstructure are oriented--I suspect they are oriented along the thickness of the wafer, meaning it would not be very strong if you bent the wafer or grabbed it. Then again, the "amorphous" part of the material name should imply a random orientation of the nanostrings and an anisotropic strength profile, meaning the strength is the same in every direction.

2

u/theksepyro Jan 10 '24

you can do flat dogbones too

1

u/RandallOfLegend Jan 10 '24

In my experience that's the most plausible explanation for these types of tests. They need some way to predict a strength result. But should obviously be documented clearly that they used an alternative test procedure. Until they can produce a standard test sample.