Durable 3D Printed Concrete Inspired by Lobster Shells

Innovation: Academia

RMIT University

2021

Image: Ed Bierman / Flickr / CC BY - Creative Commons Attribution alone

Manage Impact

An impact is a high force or mechanical shock that happens over a short period of time, such as a hammer hitting a nail rather than a hand pushing slowly against a wall. Because of their speed and force, impacts don’t allow materials to slowly adjust to the force, which can lead to cracks, ruptures, and complete breakage. Therefore, living systems have strategies that can absorb, dissipate, or otherwise survive that force without the need to add large amounts of material. For example, the Toco toucan’s large beak is very lightweight, yet can withstand impacts because it’s made of a composite material with rigid foam inside and layers of a hard, fibrous material outside.

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Prevent Deformation

When a living system undergoes compression, tension, shear, bending, or twisting, its internal inter-molecular forces can often resist these forces and even change shape temporarily, returning to the original shape when the forces stop. However, if the force is too strong or lasts too long, permanent deformation or structural failure can occur, resulting in death. Therefore, living systems have strategies to resist deformation or help ensure limited deformation. For example, bones have thin crystals and proteinaceous fibers that provide strength and flexibility, protecting them from forces that would otherwise cause deformation on a daily basis.

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Prevent Fracture/Rupture

High force impact or stress can cause materials that comprise living systems to separate into two or more pieces (called fracturing) or to break or burst suddenly (called rupturing). For example, a scallop prevents structural failure from fracture because its shell is comprised of two materials of varying stiffness. When a crack moves from the scallop’s stiff material to the less stiff one, the latter reduces the force at the tip of the crack, thereby stopping it from spreading farther.

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3D printed concrete from RMIT University is constructed with helicoid layers to increase strength.

Benefits

Increased strength
Increased resiliency
Scalable

Applications

Building materials
Bridge design

UN Sustainable Development Goals Addressed

Goal 11: Sustainable Cities & Communities

The Challenge

3D printed concrete has the potential to make building structures more efficient and sustainable by saving time, money, and materials. However, due to the layer-by-layer printing methodology, the concrete often has planes of weakness.

Innovation Details

The 3D printed concrete is laid in a helicoidal, twisting pattern rather than parallel lines, similar to the design of the lobster shell. This methodology better integrates the layers of concrete as it sets. Additionally, the concrete mixture is reinforced with steel fibers that reduce defects and porosity, allowing the concrete to harden more consistently to create a better base for the layers above.

Biological Model

Lobster shells are strong, flexible and resistant to cracking. The shell is made of fibers arranged in the Bouligand structure, a structure similar to a spiral staircase. This structure helps distribute an impact force or the bite of a predator throughout the shell, lessening the negative effects.

See how other organisms use the Bouligand structure

close up of metallic colored fish scales

Biological Strategy

Amazonian Fish Has Tough Scales to Protect From Predators

Arapaima fish scales are extremely tough because they are made of tissue arranged in the Bouligand structure

References

Journal article

Influences of Printing Pattern on Mechanical Performance of Three-Dimensional-Printed Fiber-Reinforced Concrete

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