Lobster shell patterns make concrete stronger | Hacker News Reader

Lobster shell patterns make concrete stronger

reuters.com

88 pointsquotha37 comments

Links to the press release from the university [1] and the published study [2] have more information than this. The study is more specifically how different patterns of 3D printing concrete can increase strength over the conventional unidirectional printing in parallel lines.

[1] https://www.rmit.edu.au/news/all-news/2021/jan/lobster-concr...

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

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.

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.

>>> ...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?...

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.

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.

> 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).

A criss-cross pattern is now called biomimicry?

The following article has pictures and a video:

  https://www.theconstructionindex.co.uk/news/view/lobster-shells-inspire-stronger-3d-printed-concrete

This is the normal top/bot pattern for 3D printing, right? I don't think it was copied from lobsters.

Or am I missing something? Or is this totally misrepresented?

The press release:

https://www.rmit.edu.au/news/all-news/2021/jan/lobster-concr...

Links the paper:

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

Figure 2 shows it is more than just criss-cross, the layout rotates for each layer following a pattern.

This reminds me of tabby, concrete mixed with oyster shells. You can still find all these old buildings made of it from the Colonial days in Georgia and South Carolina.

https://en.wikipedia.org/wiki/Tabby_concrete

The "tech" you find in the oceans is truly amazing.

The news release Bio-inspired: How lobsters can help make stronger 3D printed concrete [1] from RMIT University (with 1 minute video) and the paper Influences of Printing Pattern on Mechanical Performance of Three-Dimensional-Printed Fiber-Reinforced Concrete [2]:

> Underperformed interfacial bond and anisotropic properties are often observed in three-dimensional-printed concrete, where the printing pattern is unidirectional. Such issues could be potentially alleviated by replicating microstructures of natural materials or applying different architectures, where printed layers are arranged into unique and unconventional patterns.

> The addition of steel fibers leads to noticeable improvement on both compressive and flexural strengths of samples in any pattern compared with their counterparts without fibers. Besides, the inclusion of steel fibers into unconventional layups (cross-ply, quasi-isotropic, and helicoidal patterns) leads to the alleviation of directional dependence of mechanical properties, which is a limitation of the unidirectional samples with fibers.

[1] https://www.rmit.edu.au/news/all-news/2021/jan/lobster-concr...

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

As has been mentioned elsewhere, the reuters link is pretty much fluff (lobster, lobster, lobster) in that the RMIT paper https://www.liebertpub.com/doi/10.1089/3dp.2020.0172 discusses Bouligand structures and uses the lobster as a biological example. Non biological examples abound.

Structures for improving adhesion and strength in FDM printing (which arguably includes pumping concrete) is important and continually researched - basic, commercial and diy https://www.youtube.com/playlist?list=PLEOQTmIWJ_rmoqdFUCgKr...

Biomimicry is fascinating. There's some good info at the Biomimicry Institute:

https://biomimicry.org

Biology has much to offer for us. There are millions of years of evolution encapsulated in some of the biological form and structures out there.

Similarly, abalone shell patterns were considered for ceramic armor plates. https://ceramics.org/ceramic-tech-today/ceramic-video/video-...

I was watching a documentary on electricity and it said how Volta used nature as inspiration.

The alternating pattern of a Torpedo fish's muscle cells were the basis for the voltaic pile. The discs were mimicking how the many small cells of the fish combined small amounts of electricity into a larger amount.

Mmmm, Reading the title I was expecting they were developing some system that made a super strong exo skeleton with a porous interior just like lobsters, or bones.

They have done nothing like that. Criss cross printed lines? Adding reinforcement fibers?

That is as old as 3D printing.

It would be nice if there were a picture of this pattern included.

Completely unrelated, but I somehow thought https://lobste.rs had invented a new shell (script) pattern at first.

This is a common technique when laying up carbon fiber / fiberglass parts. For each layer you put down, you vary the orientation of the fibers such that you don't end up with them all pointing in the same direction. This makes the material behave more like something homogeneous, like steel or aluminum, for example.

I don't see what this has to do with lobster shells.

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