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Comment by crazygringo | Hacker News Reader

Me too. It's even worse when they talk about how the "wood" is 10 times tougher than glass.

No, it's not the wood that's tougher -- it's the epoxy resin it's been filled with that's tougher, right?

Edit: So basically it sounds like the wood matrix is a way to add tensile strength to epoxy to make it more shatter-resistant when it's in thin sheets. I guess it's tricky semantics whether the main material should be referred to as epoxy/resin or as wood, when it's their combination.

And it seems like we have competing precedents: we refer to "carbon fiber" (the wood in this comparison) rather than the resin, but we talk about buildings made of "concrete" (the epoxy resin by analogy) rather than the rebar steel within.

Thanks to the comments below for helping to explain.

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> it's the epoxy resin it's been filled with that's tougher, right?

Your comment seems to suggest that the cellulose left after removing the lignin from the wood isn't playing any role. The wood really is playing an integral role.

It's the epoxy reinforced with the cellulose remaining after lignin removal that's tougher. Just a block of cured epoxy resin isn't going to be tougher than glass.

It's a similar case with "carbon fiber" items. If you just wrapped a pressure vessel with carbon fiber, it really wouldn't help much. It's the carbon fiber reinforced resin that's strong. That tennis racket wouldn't work very well with just carbon fiber or just epoxy resin.

Yeah, same goes for reinforced concrete. Just concrete or just rebar isn't going to work nearly as well. It's the two combined that provide the powerful combination of compressive strength and tensile strength. This is the whole rationale behind composite materials: combining different materials with different properties to obtain a gestalt material.

> Just a block of cured epoxy resin isn't going to be tougher than glass.

I wouldn't be so sure -- toughness has a specific meaning (energy before fracturing), and polymers are generally going to be tougher than glass.

http://www-materials.eng.cam.ac.uk/mpsite/interactive_charts...

I haven't dug into it, but note how the article mixes up these terms to make it sound better:

> transparent wood came out around three times stronger than transparent plastics like Plexiglass and about 10 times tougher than glass.

If you plot that on those graphs it doesn't put it anywhere remarkable.

edit: This is like trying to sell an electric bike by saying that it's three times faster than walking and 1/10 the price of a car -- ok, but how does it compare to a pedal bike? It's much more obvious when you do it with words that most people understand intuitively.

Some quick numbers from a recent study:

Transparent wood tensile strength - 171 MPa

Basswood tensile strength - 2.4 MPa

PMMA plastic - 75 MPa

*Edit - Non-transparent densified wood - 398 MPa

https://www.sciencedirect.com/science/article/abs/pii/S13598... https://designerdata.nl/materials/plastics/thermo-plastics/p... https://www.matweb.com/search/datasheet.aspx?matguid=1775e21... https://pubmed.ncbi.nlm.nih.gov/35807412/

Basswood is about the worst wood you could choose. You can damage it with your hands.

They needed something porous and compressible, so it sounds like a great choice.

Well no, otherwise they would just use sheets of resin.

Even then, the wood is still stronger. If you research densified wood, it's a similar process that uses a heated chemical bath to remove the lignin but then instead of replacing it with resin, they compress the wood at temperature. It provides strengths comparable to steel by weight without adding new material to it.

I think the key word here, somewhat buried in the article, is "sustainability". If you can convince someone that what you're selling is really wood, then you get your brownie points for being green. Epoxy resin doesn't sound quite so sexy and sustainable in a planet-conscious marketplace.

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