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Bio-inspired 3D printed cement structures become stronger when they crack

Researchers at Purdue University developed bio-inspired 3D printed cement paste structures that become stronger under pressure.

The researchers took inspiration from the shells of arthropods such as lobsters and beetles. These shells are designed in such a way that they can control how damage spreads. “The exoskeletons of arthropods have crack propagation and toughening mechanisms that we can reproduce in 3D-printed cement paste,” the researchers say.

They were especially inspired by the mantis shrimp. This creature grabs its prey with an appendage that grows tougher on impact through twisting cracks that dissipate energy and prevent appendage from falling apart.

The engineers use 3D printing to create what they say are the first-ever bio-inspired structures using cement paste. 3D printing eliminates the need for a mould for each design. By using micro-CT scans, the team could better understand the behaviour of hardened 3D printed cement-based materials and take advantages of the weak characteristics.

The engineers experimented with different types of 3D printing techniques. For instance, they designed a honeycomb, a compliant, and a Bouligand structure. Each of these ‘architectures’ allowed for new behaviours once hardened. The Bouligand structure for one takes advantage of weak interfaces to make a material more crack-resistant, whole the compliant architecture makes cement-based elements act like a spring, even though it’s made of a brittle material.

The team plans to explore other ways that cement-based elements could be designed for building more resilient structures. The aim is to develop architectures that are more resilient to wild fires and earthquakes.

Photo: Purdue University Concrete 3D Printing Team/Mohamadreza Moini