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Comment by PEJOE | Hacker News Reader

Negative post here - interesting research but shame on reuters / researcher for pretending this is biomimicry. The article does not say at all how the concrete has anything to do with lobster shells.

Further, rotating layers to change the bulk performance of materials composed of anisotropic plies is very old technology developed originally for aerospace / racing applications.

Ansys has an entire package devoted to the analysis of structures made from anisotropic materials in this way.

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>>> ...rotating layers to change the bulk performance of materials composed of anisotropic plies is very old technology developed originally for aerospace / racing applications.

Indeed the original engineered composite material: Plywood.

I believe plywood has piles/fibers orthogonal to each other, in this video they were laid over diagonal to the underlying concrete.

Some higher-quality plywood does have layers whose grain is at 45 degrees to the adjacent layers: https://www.globalpp.co.uk/blog/why-do-plywood-layers-run-in...

That seems like a typo. The title says “opposite”, and just before specifying 45 degrees, the article says the layers are at a “right angle” to one another. Looking at their other products, they seem to differentiate on bonding strength and surfacing, which is pretty common.

Isn't concrete an engineered composite material to begin with? It's ancient. AFAIK plywood is an 19th century invention.

In engineering parlance composites are materials with high tensile strength bonded to materials with high compressive strength.

Concrete is compressive strength materials (rock, sand) bonded with cement. OTOH - We could say reinforced concrete, (steel, fiberglass, etc reinforcement) is a composite.

Plywood was used for shields by the Romans, I'm fairly certain the Vikings, and wikipedia mentions the Greeks and Egyptians used it as well. From what I can tell from a quick google, it does seem to be a casualty of the Dark ages though.

Maybe not. The Dutch police appear to be using wicker riot shields in 2021. Good for the environment.

https://www.bostonglobe.com/2021/01/25/nation/weekend-riotin...

I believe the implication was it was lost in the Dark Ages and re-discovered in 19thc. No reason to suggest plywood is not in use today

I remember reading in Gates of Fire [0] that the Spartans used heavy, round oak shields which suited there phalanx style of warfare.

The Persians (and their allies) used wicker shields that chose light weight over protection [1].

More recently, there was also a video floating around recently of how protesters were building Viking shield walls to protect themselves [2]

0 - https://amzn.to/39n23Jx 1 - https://en.wikipedia.org/wiki/Sparabara 2 - https://twitter.com/joshuapotash/status/1291962889323020288?...

So it is a bit click baity, sure. But how many people really think about anisotropic plies? (cool word, anisotropic, by the way)

Folks who have done 3D printing figure out pretty quickly that the orientation of the print can have a large effect on the various structural properties of the thing printed. I basically spent the first couple of months printing various test objects in different orientations to get a better understanding of this.

For that reason, the paper gives a reasonable way to approach the question of "how can I make this stronger?".

I feel like plywood is a really common thing that a lot of people know to have alternating/anisotropic layers of wood grain

Agreed, that is a great example. That an oriented strand board or OSB.

Plywood alternates grain patterns at 90° to each other. OSB uses the same technique, but with shredded wood instead of sheets.

Neither use the 3D twisting method outlined in the article.

I'm confused. They printed a helicoidal pattern, which is basically a flattened spiral which was absolutely inspired by the Lobster shell.

Why doesn't that qualify as biomimicry?

Did you actually read the article?

> Their bio-mimicking spiral patterns improved the overall durability of the 3D printed concrete...

That's like, the 4th paragraph in the article published by the university.

See FIG. 1. Hierarchical microstructure of the cuticle of the lobster (Homarus americanus; based on existing studies) from the paper:

https://www.liebertpub.com/doi/10.1089/3dp.2020.0172

> Further, rotating layers to change the bulk performance of materials composed of anisotropic plies is very old technology developed originally for aerospace / racing applications.

> Ansys has an entire package devoted to the analysis of structures made from anisotropic materials in this way.

Also, if you read your link paper, they are not doing anything different that what has been known for a long time in long-fiber composites - see: https://www.liebertpub.com/cms/10.1089/3dp.2020.0172/asset/i...

> they are not doing anything different that what has been known for a long time in long-fiber composites

They are using a new material (concrete) and in-situ fabrication technique (extrusion/printing) that is at an early stage of development and doesn't seem to be performing well. I'm assuming that the type of empirical data produced by these experiments is a prerequisite to developing a finite element model for these materials/techniques.

The worst case here is that civil engineers have to reinvent the knowledge that you believe other engineering disciplines have mastered using different materials. Computer guided in-situ reinforced concrete seems quite novel to me; perhaps that is a reflection of my own knowledge gap.

> very old

> originally for aerospace / racing applications

That's a wild take on "very old"!

I bet you can find even older examples, e.g., textiles

Composite bows were made thousands of years ago using this principle. Tendons glued in alternating layers.

I suppose shooting an arrow is a primitive form of aerospace (missile).

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