Springy, twisty and crack resistant are not terms often associated with cement. However, research into 3D printing for construction at Purdue University, Indiana, is going against the grain.
By investigating current weaknesses (such as non-uniformity in microstructure) present in 3D printed cement structures, a team from the Lyles School of Civil Engineering and School of Materials Engineering are challenging the brittle nature of these materials.
Mohamadreza “Reza” Moini, is a PhD candidate in civil engineering at Purdue, and co-author on a new paper detailing the fabrication of the meta-performing cement structures. “What’s novel about our work,” explains Moini, “is that using 3D printing we incorporate bio-inspired architectures that provide resilience, flaw-tolerance, and fracture-resistance to a material that’s intrinsically brittle.”
The work takes inspiration from the naturally hard shell structures of arthropods, insects and crustaceans that have an exoskeleton in place of a skin. These shells take on different naturally-occurring structures, such as compliant design, honeycomb architecture, auxetic architecture, and Bouligand structures – which is of particular interest to this most recent study.
Design that packs a punch
The dactyl club of a mantis shrimp is given as an example of a Bouligand design in the study. The team explains, “Previous research has shown that these Bouligand architectures, found in the endocuticles of arthropods (such as mantis shrimp), tend to grow cracks in twisted patterns following the direction of the fiber,”
“These twisting patterns have been found to be responsible for increasing toughness and promote the spread of the damage.”
Bouligand patterns are replicated in the research using 3D printed cement. When tested, these samples proved to have delocalized damage control, with “enhanced fracture and damage tolerance, and unique load‐displacement response, all without sacrificing strength.”
The team also employs micro CT imaging to identify the weaknesses of 3D printed cement structures in order to improve their designs.
3D printing and the built environment
The vision of Purdue University’s cement 3D printing research is to apply these structural designs for the construction of stronger buildings.
Currently the work is done at a small scale, but if applied to large-format projects, such designs could lead to an advancements in the built environment.
Stress Line Additive Manufacturing (SLAM) is another technique under experimentation for its potential to reinforce large 3D printed structures.
Purdue’s “Additive Manufacturing and Performance of Architectured Cement‐Based Materials,” from Mohamadreza Moini, Jan Olek, Jeffrey P. Youngblood, Bryan Magee, Pablo D. Zavattieri is published online in Advanced Materials journal.
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Featured image shows an example Bouligand design for 3D printed cement. Image via Purdue University