3 ms·

> While composites might seem like a futuristic technology, in many ways, they hark back to millions of years of human and even pre-human material technology. W

> While composites might seem like a futuristic technology, in many ways, they hark back to millions of years of human and even pre-human material technology. Wood, after all, is the original composite material, as it’s composed of long and short fibers glued together by other substances—much like modern synthetic composites are often made up of carbon fiber held together by epoxy resins. Wood was a chief enabler of the success of our species, and it exhibits many of the advantages and disadvantages of composites. Not to nitpick too much, but while wood is "technically" a composite material made up of fiber embedded in lignin, I don't think it's very useful to include it under the broad category of composite materials. Engineered woods like plywood and cross-laminated timber definitely are, but it's more useful to classify regular wood as an organic raw material rather than a composite. The first composite material humans had any experience with was probably silcrete. It's naturally occurring but ancient humans figured out how to strengthen it by heat treating it in a fire (80-160 kYa). The first time humans intentionally made a composite material is adobe/mudbrick (11 kYa), wattle and daub (6 kYa), plywood in Mesopotamia (5.4 kYa), cob (4 kYa), and finally Romans developed something resembling concrete (I dont remember kYa).

slabity 2y ago
> Not to nitpick too much, but while wood is "technically" a composite material made up of fiber embedded in lignin, I don't think it's very useful to include it under the broad category of composite materials. Engineered woods like plywood and cross-laminated timber definitely are, but it's more useful to classify regular wood as an organic raw material rather than a composite. Why would defining it as a raw material be "more useful"? Why is defining it as a composite "less useful"?
- jessriedel 2y ago
  Yea from a material science perspective, wood seems to obviously be a composite.
  - aranchelk 2y ago
    Not just that. When learning about the anisotropic nature of composites (different strengths in different directions) wood is a tangible example for anyone who’s done arts and crafts, woodworking, etc.
aardvarkr 2y ago
I think they’re just trying to make composite more relatable to the Everyman without actually understanding it themselves. At least they’re trying.
- refulgentis 2y ago
  They're trying, and succeeding, and it's beautiful analogy akin to ones my best physics professors would provide.
hn_throwaway_99 2y ago
Kinda feels like you're missing the point of the quoted sentence. That is, it's not that wood is actually a composite material as we define it now, but that wood has the characteristics of a composite, i.e. different substances intertwined in a way to give better properties than any individual material alone, and going with the theme of the article, this is a direct contrast to materials like steel or plastic.
- jaggederest 2y ago
  The other important property that wood shares with modern manmade composites is that it is anisotropic - i.e., it is stronger in some directions of force than others. You can use bodyweight to snap a short grain board that would, if it were long grain, hold up under a ton or more.
  - fifticon 2y ago
    note when you make OSB2 and OSB3, you to some degree can make up for this(?)
dreamcompiler 2y ago
Wood was a chief enabler of the success of our species Wood was the chief enabler of trees. Trees have to be big, strong, lightweight, and bendable. Homogeneous materials won't work for that application. You need a composite. So evolution invented one. Even more amazing: Trees 3D print themselves out of carbon dioxide.
- shiroiushi 2y ago
  >Trees have to be big, strong, lightweight, and bendable. Homogeneous materials won't work for that application. Why wouldn't titanium work for that application? (Assume that somehow the plant can move nutrients and fluids around some other way.) Or even steel, as long as it's not solid? Obviously, nature can't produce hollow steel tubes, but lots of metals satisfy your requirement list here.
  - alanbernstein 2y ago
    I think mainly because trees are not steel plants
  - bartc 2y ago
    Trees did not evolve with bountiful access to titanium, but it would be interesting to ponder how they would have evolved on a metal planet
    - Qwertious 2y ago
      >but it would be interesting to ponder how they would have evolved on a metal planet It overlaps a whole lot with the concept of a dyson trees, but the core problem is that it needs to be able to use the metal in the first place - earth is a metal planet, in the sense that ~10% of the planet is iron, and yet our trees are not steel.
      - joha4270 2y ago
        I don't really think that's a fair assessment, since most of it is in the core. That's some very long and heat resistant roots. I also can't help but wonder, could trees even use iron if it was plentiful in the upper crust? You need a lot of energy to separate iron oxide into elemental iron. Betting against what evolution can make is usually a bad idea, but that would be a neat trick.
2four2 2y ago
I disagree. In advanced materials, we analyze materials categorically. In this instance, the way we would calculate the structure of wood is based on its isotropy, or more simply, its symmetry of strength and stiffness. The way wood behaves anisotropically means its structure is calculated the same way as most other composites. Composite Laminate Theory is the primary way that structure behavior is calculated for both wood laminates and carbon fiber laminates. We squarely categorize it in the same bin as carbon fiber, but that's just one perspective from one discipline, so take it as you will.
andrewflnr 2y ago
I don't know how I escaped learning about silcrete so far, being interested in both geology and primitive technology. Thanks for the tip! For anyone that curious: https://en.wikipedia.org/wiki/Silcrete https://en.wikipedia.org/wiki/Silcrete
marcus_holmes 2y ago
> and finally Romans developed something resembling concrete (I dont remember kYa). About 2 kYa, give or take a couple of centuries. And it was actual concrete, rather than something resembling concrete. In fact, better than the concrete we were making a hundred years ago, and better than most of our concrete fifty years ago. Roman aqueducts and bridges are still standing 2000 years later. Not sure I'd put money on the same being true of our stuff.
- tim333 2y ago
  Yeah there was a theory discussed on HN a couple of years ago that superior qualities came from mixing in quicklime (CaO). I'm not sure if they've developed that and tested it against modern concretes. I guess it's hard to tell if they'll last 2000 years without waiting quite a while. (https://news.ycombinator.com/item?id=34280239 https://news.ycombinator.com/item?id=34280239)
  - marcus_holmes 2y ago
    I heard it was that they used seawater not freshwater. And yes, we'll have to wait a while. Though probably not 2000 years - we only have to wait until our concrete starts failing, which might be a lot sooner than that.
AYBABTME 2y ago
I think it's actually very fair to count wood as a composite. Composite is the concept, and wood happens to be a natural occurrence of the concept. Keeping it qualified as a composite also helps expand the mind: composites don't need to manufactured how we're typically manufacturing it in the present. When you think of wood as a composite, it's an opportunity for ah-ha moments in students.

slabity 2y ago

> Not to nitpick too much, but while wood is "technically" a composite material made up of fiber embedded in lignin, I don't think it's very useful to include it under the broad category of composite materials. Engineered woods like plywood and cross-laminated timber definitely are, but it's more useful to classify regular wood as an organic raw material rather than a composite. Why would defining it as a raw material be "more useful"? Why is defining it as a composite "less useful"?

jessriedel 2y ago
Yea from a material science perspective, wood seems to obviously be a composite.
- aranchelk 2y ago
  Not just that. When learning about the anisotropic nature of composites (different strengths in different directions) wood is a tangible example for anyone who’s done arts and crafts, woodworking, etc.

aardvarkr 2y ago

I think they’re just trying to make composite more relatable to the Everyman without actually understanding it themselves. At least they’re trying.

refulgentis 2y ago
They're trying, and succeeding, and it's beautiful analogy akin to ones my best physics professors would provide.

hn_throwaway_99 2y ago

Kinda feels like you're missing the point of the quoted sentence. That is, it's not that wood is actually a composite material as we define it now, but that wood has the characteristics of a composite, i.e. different substances intertwined in a way to give better properties than any individual material alone, and going with the theme of the article, this is a direct contrast to materials like steel or plastic.

jaggederest 2y ago
The other important property that wood shares with modern manmade composites is that it is anisotropic - i.e., it is stronger in some directions of force than others. You can use bodyweight to snap a short grain board that would, if it were long grain, hold up under a ton or more.
- fifticon 2y ago
  note when you make OSB2 and OSB3, you to some degree can make up for this(?)

dreamcompiler 2y ago

Wood was a chief enabler of the success of our species Wood was the chief enabler of trees. Trees have to be big, strong, lightweight, and bendable. Homogeneous materials won't work for that application. You need a composite. So evolution invented one. Even more amazing: Trees 3D print themselves out of carbon dioxide.

shiroiushi 2y ago
>Trees have to be big, strong, lightweight, and bendable. Homogeneous materials won't work for that application. Why wouldn't titanium work for that application? (Assume that somehow the plant can move nutrients and fluids around some other way.) Or even steel, as long as it's not solid? Obviously, nature can't produce hollow steel tubes, but lots of metals satisfy your requirement list here.
- alanbernstein 2y ago
  I think mainly because trees are not steel plants
- bartc 2y ago
  Trees did not evolve with bountiful access to titanium, but it would be interesting to ponder how they would have evolved on a metal planet
  - Qwertious 2y ago
    >but it would be interesting to ponder how they would have evolved on a metal planet It overlaps a whole lot with the concept of a dyson trees, but the core problem is that it needs to be able to use the metal in the first place - earth is a metal planet, in the sense that ~10% of the planet is iron, and yet our trees are not steel.
    - joha4270 2y ago
      I don't really think that's a fair assessment, since most of it is in the core. That's some very long and heat resistant roots. I also can't help but wonder, could trees even use iron if it was plentiful in the upper crust? You need a lot of energy to separate iron oxide into elemental iron. Betting against what evolution can make is usually a bad idea, but that would be a neat trick.

2four2 2y ago

I disagree. In advanced materials, we analyze materials categorically. In this instance, the way we would calculate the structure of wood is based on its isotropy, or more simply, its symmetry of strength and stiffness. The way wood behaves anisotropically means its structure is calculated the same way as most other composites. Composite Laminate Theory is the primary way that structure behavior is calculated for both wood laminates and carbon fiber laminates. We squarely categorize it in the same bin as carbon fiber, but that's just one perspective from one discipline, so take it as you will.

andrewflnr 2y ago

I don't know how I escaped learning about silcrete so far, being interested in both geology and primitive technology. Thanks for the tip! For anyone that curious: https://en.wikipedia.org/wiki/Silcrete https://en.wikipedia.org/wiki/Silcrete

marcus_holmes 2y ago

> and finally Romans developed something resembling concrete (I dont remember kYa). About 2 kYa, give or take a couple of centuries. And it was actual concrete, rather than something resembling concrete. In fact, better than the concrete we were making a hundred years ago, and better than most of our concrete fifty years ago. Roman aqueducts and bridges are still standing 2000 years later. Not sure I'd put money on the same being true of our stuff.

tim333 2y ago
Yeah there was a theory discussed on HN a couple of years ago that superior qualities came from mixing in quicklime (CaO). I'm not sure if they've developed that and tested it against modern concretes. I guess it's hard to tell if they'll last 2000 years without waiting quite a while. (https://news.ycombinator.com/item?id=34280239 https://news.ycombinator.com/item?id=34280239)
- marcus_holmes 2y ago
  I heard it was that they used seawater not freshwater. And yes, we'll have to wait a while. Though probably not 2000 years - we only have to wait until our concrete starts failing, which might be a lot sooner than that.

AYBABTME 2y ago

I think it's actually very fair to count wood as a composite. Composite is the concept, and wood happens to be a natural occurrence of the concept. Keeping it qualified as a composite also helps expand the mind: composites don't need to manufactured how we're typically manufacturing it in the present. When you think of wood as a composite, it's an opportunity for ah-ha moments in students.