6 ms·

Just a heads up - strength is not a single metric. There is tensile (pulling), compression, and shear (sliding) strength. There's also Young's modulus (how much

Just a heads up - strength is not a single metric. There is tensile (pulling), compression, and shear (sliding) strength. There's also Young's modulus (how much something stretches), fatigue limits (steel can work perpetually with deformations under a certain threshold). There's also specific strength (strength per kg) vs strength per volume and strength per dollar. Steel also comes in lots of different flavors, with very different (orders of magnitude) strengths.

olliej 5y ago
Yeah I was annoyed about how the article didn’t say what strength they were measuring. Not of course saying improvement in any of those metrics is bad, but the comparison being made needs to say what is being compared, and how it compares to the existing best in class.
SAI_Peregrinus 5y ago
Also those metrics can vary with direction. For steel they're usually pretty uniform, but this new substance forms "2D sheets" so it's likely strength will be highly directional. Maximum tensile and compressive strength are likely to be 90° apart.
- robbedpeter 5y ago
  It can form films, which they tested because coatings for things like solar panels and cars and tools are profitable. They also tested bulk plastic. It takes a long time to set, with hours in a gel phase, so epoxy-like mold pouring, flooring, and other bulk plastic applications are likely. It might be awesome for bullet proof armor, safety equipment, and lightweight cordage and fabrics. The synthesis is simple - it's an advance using polarized light at particular wavelengths in novel chemistry, probably inspired by the recent discovery in electrochemistry that can impose specific chirality on well known reactions.
exo-pla-net 5y ago
> The researchers found that the new material’s elastic modulus — a measure of how much force it takes to deform a material — is between four and six times greater than that of bulletproof glass. They also found that its yield strength, or how much force it takes to break the material, is twice that of steel, even though the material has only about one-sixth the density of steel.
- saxonww 5y ago
  The problem with this is that steel is a large class of alloys, with a wide variety of properties depending on the chemical and physical makeup of an alloy. Even "types of steel" that people are familiar with - e.g. stainless steel - are not specific alloys but themselves classes of alloys. I'm not a metallurgist but I assume there are dozens if not hundreds of alloys qualifying as steel. So when someone writes an article saying "it's stronger than steel!" that's exciting, but it's not enough information. In this case we know it's stronger by yield strength. We can say the new material's yield strength is twice that of the weakest known steel alloy, but no more than that. A quick look around found this: https://amesweb.info/Materials/Steel-Tensile-Yield-Strength-Chart.aspx https://amesweb.info/Materials/Steel-Tensile-Yield-Strength-... You can see here, there is a wide gulf between the weakest and strongest alloys just in this chart, which only has five alloys and a handful of different treatments. Yield strength is anywhere from 210MPa to over 1600MPa, an 8x difference. This page has some charts for the new material: https://www.researchgate.net/figure/Mechanical-properties-of-2DPA-1-nanofilms-a-Optical-micrograph-of-a-339-nm-thick_fig3_350398258 https://www.researchgate.net/figure/Mechanical-properties-of... Subchart (g) in the image shows a plot of yield strength against elastic modulus, and it looks like the plot tops out around 1.4 GPa, meaning the strongest tested configuration by yield strength is weaker than that of tempered 4140 and 4340 steels, while nearly 7x stronger than hot-rolled 1020 steel. I don't know if "2D yield strength" is different than what is shown in the amesweb.info table, though.
  - burnished 5y ago
    I think you're missing the novel polymer for the steel-forest. Its a 2d polymer (spans a plane instead of forming strings, which is new) that has material properties that make it comparable to materials that we think of as strong. The part where it gets rigorously classified can come later. The people involved with this project were themselves probably not metallurgists.
- TheSpiceIsLife 5y ago
  > yield strength, or how much force it takes to break the material That's not yield strength. Yield strength is how much force is required to permanently deform the material. Ultimate tensile strength is the force required to break the material. One great thing about steels is that they tend to work-harden. Typical 250 grade mild steel, meaning it takes in excess of 250 MPa force to permanently stretch a 10mm round diameter section, usually has an ultimate tensile strength exceeding 400 MPa.
jimmytucson 5y ago
I’ve often heard that spider silk is stronger per kg (or is it per m^3?) than steel. Are they talking about pulling, compressing, sliding, or all of the above?
- TylerE 5y ago
  Plenty of things are stronger than steel on a per pound basis. For instance, many aluminum alloys have about 60-80% the tensile strength of steel, but only 1/3rd the weight.
  - lazide 5y ago
    Titanium even more so. For those, they are actively swapped around where cost vs weight trade offs happen. steel vs aluminum vs magnesium, vs titanium in engineering application, where for example engine blocks, airplane parts, car parts, battery components, etc. all have a long history of this. It’s a complicated process because the trade offs are not simple cost/weight/strength. Steel has an nearly infinite fatigue lifetime for instance, so steel springs are great. Aluminum does not, so aluminum springs are terrible - among other things. No amount of weight savings can likely fix that problem in a useful way. These pose big challenges in aircraft in particular where aluminum skins and fuselages make flight doable/economic, but means pressurized aircraft in particular have a finite lifespan in pressurization cycles/takeoffs and landings before they fall apart, no matter how nicely you treat them. Several major accidents (including the top of an airliner coming off and sucking a flight attendant out over the pacific on the way to Hawaii) happened before this was fully understood. Titanium is in theory much better, but is incredibly difficult to work with(requiring forgings in most cases, and being almost unmachinable), and very expensive as the bond it forms with oxygen is so strong the normal fluorine based processing used with Aluminum won’t work. Yeah, you read that right. Fire danger (such as magnesium engine blocks burning) is also a non trivial thing to mitigate. Titanium can be one of the worst offenders here (powdered titanium fires can burn SAND used to try to put it out as an oxidizer), which makes working with it hazardous in some cases. Iron, which will also burn, is generally so mellow when it does that burning it is a normal operation while scrapping and cutting it and you can’t get a runaway from doing so except in truly difficult to achieve circumstances (it’s what an oxy-acetylene cutting torch is doing).
holoduke 5y ago
Exactly. We also have temperature and chemical resistance. Very important in most applications and for example an interesting discussion between rubber and polyurethane compounds.
thereddaikon 5y ago
There are also other metrics that are often confused with strength but have distinct definitions such as toughness, hardness, and wear resistance.
albrewer 5y ago
> steel can work perpetually with deformations under a certain threshold[*] [*] Within a temperature range of about ~-30 °C to ~400 °C. Below that and the toughness goes way down so that it's prone to cracking. Above that and carbon starts to work its way into all those crystal structure discontinuities, preventing some percentage of the strain from being relieved each stress cycle (the "creep range"). That's just for carbon steels. Stainless has a different set of problems.
- bungle 5y ago
  > Within a temperature range of about ~-30 °C to ~400 °C. If the new material is plastic-like, it may have worse issues here?
  - albrewer 5y ago
    Maybe? PTFE (Teflon) has a melting point around 325 °C; this plastic could be higher. The point of my comment was to qualify what the person above me stated.
sho_hn 5y ago
Book tip: "Structures: Or Why Things Don't Fall Down" by J. E. Gordon. As a layman, I greatly enjoyed this one as a primer.

olliej 5y ago

Yeah I was annoyed about how the article didn’t say what strength they were measuring. Not of course saying improvement in any of those metrics is bad, but the comparison being made needs to say what is being compared, and how it compares to the existing best in class.

SAI_Peregrinus 5y ago

Also those metrics can vary with direction. For steel they're usually pretty uniform, but this new substance forms "2D sheets" so it's likely strength will be highly directional. Maximum tensile and compressive strength are likely to be 90° apart.

robbedpeter 5y ago
It can form films, which they tested because coatings for things like solar panels and cars and tools are profitable. They also tested bulk plastic. It takes a long time to set, with hours in a gel phase, so epoxy-like mold pouring, flooring, and other bulk plastic applications are likely. It might be awesome for bullet proof armor, safety equipment, and lightweight cordage and fabrics. The synthesis is simple - it's an advance using polarized light at particular wavelengths in novel chemistry, probably inspired by the recent discovery in electrochemistry that can impose specific chirality on well known reactions.

exo-pla-net 5y ago

> The researchers found that the new material’s elastic modulus — a measure of how much force it takes to deform a material — is between four and six times greater than that of bulletproof glass. They also found that its yield strength, or how much force it takes to break the material, is twice that of steel, even though the material has only about one-sixth the density of steel.

saxonww 5y ago
The problem with this is that steel is a large class of alloys, with a wide variety of properties depending on the chemical and physical makeup of an alloy. Even "types of steel" that people are familiar with - e.g. stainless steel - are not specific alloys but themselves classes of alloys. I'm not a metallurgist but I assume there are dozens if not hundreds of alloys qualifying as steel. So when someone writes an article saying "it's stronger than steel!" that's exciting, but it's not enough information. In this case we know it's stronger by yield strength. We can say the new material's yield strength is twice that of the weakest known steel alloy, but no more than that. A quick look around found this: https://amesweb.info/Materials/Steel-Tensile-Yield-Strength-Chart.aspx https://amesweb.info/Materials/Steel-Tensile-Yield-Strength-... You can see here, there is a wide gulf between the weakest and strongest alloys just in this chart, which only has five alloys and a handful of different treatments. Yield strength is anywhere from 210MPa to over 1600MPa, an 8x difference. This page has some charts for the new material: https://www.researchgate.net/figure/Mechanical-properties-of-2DPA-1-nanofilms-a-Optical-micrograph-of-a-339-nm-thick_fig3_350398258 https://www.researchgate.net/figure/Mechanical-properties-of... Subchart (g) in the image shows a plot of yield strength against elastic modulus, and it looks like the plot tops out around 1.4 GPa, meaning the strongest tested configuration by yield strength is weaker than that of tempered 4140 and 4340 steels, while nearly 7x stronger than hot-rolled 1020 steel. I don't know if "2D yield strength" is different than what is shown in the amesweb.info table, though.
- burnished 5y ago
  I think you're missing the novel polymer for the steel-forest. Its a 2d polymer (spans a plane instead of forming strings, which is new) that has material properties that make it comparable to materials that we think of as strong. The part where it gets rigorously classified can come later. The people involved with this project were themselves probably not metallurgists.
TheSpiceIsLife 5y ago
> yield strength, or how much force it takes to break the material That's not yield strength. Yield strength is how much force is required to permanently deform the material. Ultimate tensile strength is the force required to break the material. One great thing about steels is that they tend to work-harden. Typical 250 grade mild steel, meaning it takes in excess of 250 MPa force to permanently stretch a 10mm round diameter section, usually has an ultimate tensile strength exceeding 400 MPa.

jimmytucson 5y ago

I’ve often heard that spider silk is stronger per kg (or is it per m^3?) than steel. Are they talking about pulling, compressing, sliding, or all of the above?

TylerE 5y ago
Plenty of things are stronger than steel on a per pound basis. For instance, many aluminum alloys have about 60-80% the tensile strength of steel, but only 1/3rd the weight.
- lazide 5y ago
  Titanium even more so. For those, they are actively swapped around where cost vs weight trade offs happen. steel vs aluminum vs magnesium, vs titanium in engineering application, where for example engine blocks, airplane parts, car parts, battery components, etc. all have a long history of this. It’s a complicated process because the trade offs are not simple cost/weight/strength. Steel has an nearly infinite fatigue lifetime for instance, so steel springs are great. Aluminum does not, so aluminum springs are terrible - among other things. No amount of weight savings can likely fix that problem in a useful way. These pose big challenges in aircraft in particular where aluminum skins and fuselages make flight doable/economic, but means pressurized aircraft in particular have a finite lifespan in pressurization cycles/takeoffs and landings before they fall apart, no matter how nicely you treat them. Several major accidents (including the top of an airliner coming off and sucking a flight attendant out over the pacific on the way to Hawaii) happened before this was fully understood. Titanium is in theory much better, but is incredibly difficult to work with(requiring forgings in most cases, and being almost unmachinable), and very expensive as the bond it forms with oxygen is so strong the normal fluorine based processing used with Aluminum won’t work. Yeah, you read that right. Fire danger (such as magnesium engine blocks burning) is also a non trivial thing to mitigate. Titanium can be one of the worst offenders here (powdered titanium fires can burn SAND used to try to put it out as an oxidizer), which makes working with it hazardous in some cases. Iron, which will also burn, is generally so mellow when it does that burning it is a normal operation while scrapping and cutting it and you can’t get a runaway from doing so except in truly difficult to achieve circumstances (it’s what an oxy-acetylene cutting torch is doing).

holoduke 5y ago

Exactly. We also have temperature and chemical resistance. Very important in most applications and for example an interesting discussion between rubber and polyurethane compounds.

thereddaikon 5y ago

There are also other metrics that are often confused with strength but have distinct definitions such as toughness, hardness, and wear resistance.

albrewer 5y ago

> steel can work perpetually with deformations under a certain threshold[*] [*] Within a temperature range of about ~-30 °C to ~400 °C. Below that and the toughness goes way down so that it's prone to cracking. Above that and carbon starts to work its way into all those crystal structure discontinuities, preventing some percentage of the strain from being relieved each stress cycle (the "creep range"). That's just for carbon steels. Stainless has a different set of problems.

bungle 5y ago
> Within a temperature range of about ~-30 °C to ~400 °C. If the new material is plastic-like, it may have worse issues here?
- albrewer 5y ago
  Maybe? PTFE (Teflon) has a melting point around 325 °C; this plastic could be higher. The point of my comment was to qualify what the person above me stated.

sho_hn 5y ago

Book tip: "Structures: Or Why Things Don't Fall Down" by J. E. Gordon. As a layman, I greatly enjoyed this one as a primer.