Super Wood (2018) | Hacker News Reader

Super Wood (2018)

scientificamerican.com

78 pointsbingden23 comments

It would be appreciated if they used actual units and photos of the "super wood."

"Stronger than (some low ball grade of) steel" is not a unit as it's super easy to sandbag the thing you're comparing to and mislead people about how important the development is.

Are units like MPa or psi not commonly understood by the science-curious public? Why would someone like Scientific American not use actual units? This stuff is taught to basically everyone in high school.

(Maybe this is just the graduate student instructor in me, but it bothers me to no end that regular units are not used...)

EDIT: The paper does, of course use proper units (annoyingly, not in the abstract...).

The densified "super wood" gets a specific strength (strength per unit density) of: 422.2 ± 36.3 MPa/(grams/cm^3).

It is an impressive figure. State of the art carbon fiber is ~3900 MPa/(g/cm^3), though, and lots of other fibers are higher than this "super wood" (including the best grades of Balsa, I believe).

Very thin gauge high performance steel ("piano wire") can exceed this slightly (428MPa/(g/cc))

Good list: https://en.wikipedia.org/wiki/Specific_strength

Thanks for the interesting comparison.

I can imagine the folks who make plywood and pressure treat wood could just add another process and make a new in-demand product.

In another article, they have to explain kelvin, "that is, degrees above absolute zero". Imagine it's helpful for younger children.

> "coffee-table book–size slab"

...an egregious and tortured alternative to using actual units. They made it coffee table sized? They made it book sized? Do all "coffee-table books" come in the same size? Are they using the coffee-table coffee-table book from Seinfeld?

It's worse than a "Library of Congress" quantity of information, or a "football field" of land area.

Would it be so hard just to say "square centimeters", or the more America-friendly "square inches"?

Are units like MPa or psi not commonly understood by the science-curious public?

Well no, nor is the term "strength". Is it yield strength, fracture toughness, youngs modulus, etc, etc? Is that tensile, compression or shear you are talking about? Carbon fibre is strong, but how about if you hit it with a brick, then normal wood is "stronger". And then there is anisotropic behavior... This stuff is complex.

There's so many ways to look at timber strengths, and the article lightly covers how their process increases different facets:

> The team’s compressed wood is three times as dense as the untreated substance, Hu says, adding that its resistance to being ripped apart is increased more than 10-fold. It also can become about 50 times more resistant to compression and almost 20 times as stiff. The densified wood is also substantially harder, more scratch-resistant and more impact-resistant

I'm not sure if Specific Strength is something I've ever encountered wrt timber, because it depends on its use whether its compression, elasticity, hardness, or other that determines whether it's good for a specific use. That said, in my country we typically use F numbers, which are (I think) based around a loose series of terms related to stress.

For instance, here's an Oz timber that I know is pretty hard: https://ironwood.com.au/grey-ironbark-technical-specs/

That said "stronger than steel" is what ironbark is renowned for. My brother, a cabinet maker, just made some furniture form the stuff and before the job, his thicknesser and jointer blades were pristine. Afterwards, they're badly chipped. Sparks literally fly when machining this stuff.

Link to Nature paper (http://nature.com/articles/doi:10.1038/nature25476) with some nice photos.

This could be an interesting Science Fair experiment:

1. Get the following from Amazon (or your favorite online store) NaoH, $14 (https://www.amazon.com/FDC-99-Pure-Sodium-Hydroxide/dp/B013K...). Also get Na2SO3, $16 (https://www.amazon.com/Sodium-Sulfite-Na2SO3-Powder-Space-Sa...) and deionized water, $24 (https://www.amazon.com/Deionized-Water-Gallon-ASTM-Type/dp/B...)

2. Get an oak block (See paper for other types of woods that can be used) from Home Depot, $14 (https://www.homedepot.com/p/Builders-Choice-1-in-x-2-in-x-8-...)

3. Place 2.5M NaOH and 0.4M Na2SO3 in a pot, boil. Place small block of oak in it. Boil for 7 hours. Of course, should do this outdoors or in a hood.

4. In a separate container bring ionized water to boil, immerse piece of wood several times in it.

5. Press wood block perpendicular to the wood growth direction at 100 °C under a pressure of about 5 MPa (~50x atmospheric pressure) for about 1 day

6. You have your super wood to test

Step 3 is possible for hard-core science fans to do at home, Step 5 is problematic for that scenario.

Cool idea. Also consider this transparent wood experiment: https://www.instructables.com/id/Transparent-Wood/

Yeah you have to build a three story pile of barbell weights. A sizeable fraction of that would be doable just to see what happens though.

(45 lb / (225mm)^2 * pi * g) in psi = 1.8 psi

5 MPa / 1.8 psi = 403 plates * 1.25" in m = 12.8 meters

You could probably make a bottle jack press for step 5, this is probably the most obvious limiting step for size without access to industrial equipment though

Link to actual paper, much more interesting than the article, lots of pictures! https://www.fpl.fs.fed.us/documnts/pdf2018/fpl_2018_song001....

Prior discussion on HN: https://news.ycombinator.com/item?id=16331375

>Perhaps most importantly, the densified wood is also moisture-resistant: In lab tests, compressed samples exposed to extreme humidity for more than five days swelled less than 10 percent—and in subsequent tests, Hu says, a simple coat of paint eliminated that swelling entirely.

This is an improvement, but it doesn’t appear to solve the fundamental problem: rain. In practice most structural materials must survive exposure to not just humid air but liquid water — this is why Sorel cement is not used in construction, for example.

Hmm, does the right paint not deal with that?

Some woods are ok with rain - I've used cypress for outdoor signage for instance and it takes rain well - no warping or that sort of business. If you constrain expansion to one or two dimensions it might be ok.

Rain and standing water caused by rain.

Wicking can be a bitch, and some wood products do not bounce back. Wet a 2x4 and as long as you dry it before rot sets in, good as new. Fiber board, at the other end of the spectrum, ruined forever. There are a lot of things in between.

So they said paint prevents swelling but they don't say what happens to the swelled wood after it dries.

This is a great followup to the steel issue raised by Gates discussed earlier here. https://news.ycombinator.com/item?id=20813496

It seems like the carbon cost for creating this stuff might be much less.

"The material does not protect quite as well as a Kevlar sheet of the same thickness—but it only costs about 5 percent as much" - Incredible. Millions could be saved to protect the military and police. Additionally it could provide less weighty armor and improve performance. There has been a lot of talk about the weight of full military body armor, and I wonder how much this new material would weigh, and if comparable to kevlar but lighter, could improve performance. https://www.military.com/daily-news/2018/09/25/army-body-arm...

It's almost certainly heavier than the kevlar equivalent. It might be a good material for quickly building fixed fortifications though, or more cheaply armoring vehicles.

I wish this article had some photos, particularly of the transparent wood.

https://www.google.com/search?q=transparent+wood&rlz=1C1GCEA...

There is also the so-called "delta wood" (resin-wood multi-ply veneer) that was used in some of the WW2 fighters' airframes.

The Mosquito also known as 'The Wooden Wonder' - fastest thing in the sky til the Germans got the Me-262 off the ground.

Didn't do well in the far East because of humidity but they cracked that later.

Brilliant bit of engineering since it used a lot of equipment/skills that where under utilised at the time they started building them.

With the F18 and the Lightning one of my top 3 favourite military planes ever.

Is this basically a precursor to modern glulam?

https://en.m.wikipedia.org/wiki/Glued_laminated_timber

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