The natural strength of lobster shells inspired the research team. Lobster x-ray image by Florian Elias Rieser, licensed under a Creative Commons Attribution-Share Alike 4.0 International licence

In a new experimental study, researchers at RMIT University – which is based in Melbourne, Australia – looked to the natural strength of lobster shells to design 3D printing patterns. 

Their bio-mimicking spiral patterns improved the overall durability of the 3D-printed concrete, as well as enabling the strength to be precisely directed for structural support where needed.

Combined the twisting patterns with a concrete mix enhanced with steel fibres resulted in a material was stronger than traditionally-made concrete.

Lead researcher Dr Jonathan Tran said 3D printing and additive manufacturing opened up opportunities in construction for boosting both efficiency and creativity.  “3D concrete printing technology has real potential to revolutionise the construction industry, and our aim is to bring that transformation closer,” said Tran, a senior lecturer in structured materials and design at RMIT.

 “Our study explores how different printing patterns affect the structural integrity of 3D-printed concrete, and for the first time reveals the benefits of a bio-inspired approach in 3DCP. 

“We know that natural materials like lobster exoskeletons have evolved into high-performance structures over millions of years, so by mimicking their key advantages we can follow where nature has already innovated.”

The research team in RMIT’s School of Engineering focuses on 3D-printing concrete, exploring ways to enhance the finished product through different combinations of printing pattern design, material choices, modelling, design optimisation and reinforcement options.

The most conventional pattern used in 3D printing is unidirectional, where layers are laid down on top of each other in parallel lines.  

The new study published in a special issue of 3D Printing & Additive Manufacturing investigated the effect of different printing patterns on the strength of steel fibre-enhanced concrete.

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Previous research by the RMIT team found that including 1-2% steel fibres in the concrete mix reduces defects and porosity, increasing strength. The fibres also help the concrete harden early without deformation, enabling higher structures to be built.

Concrete 3D printed in patterns inspired by the internal structure of lobster shells
Concrete 3D printed in patterns inspired by the internal structure of lobster shells

The team tested the impact of printing the concrete in helicoidal patterns (inspired by the internal structure of lobster shells), cross-ply and quasi-isotropic patterns (similar to those used for laminated composite structures and layer-by-layer deposited composites) and standard unidirectional patterns. 

The results showed strength improvement from each of the patterns, compared with unidirectional printing, but Tran said the spiral patterns hold the most promise for supporting complex 3D-printed concrete structures. 

“As lobster shells are naturally strong and naturally curved, we know this could help us deliver stronger concrete shapes like arches and flowing or twisted structures,” he said.

“This work is in early stages so we need further research to test how the concrete performs on a wider range of parameters, but our initial experimental results show we are on the right track.” 

Further studies will be supported through a new large-scale mobile concrete 3D-printer recently acquired by RMIT. The 5×5m robotic printer will be used by the team to research the 3D printing of houses, buildings and large structural components.

The team will also use the machine to explore the potential for 3D printing with concrete made with recycled waste materials such as soft plastic aggregate.

The work is connected to a new project with industry partners Replas and SR Engineering, focusing on sound-dampening walls made from post-consumer recycled soft plastics and concrete, which was recently supported with an Australian Government Innovations Connections grant.

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