Princeton University Engineers Tough Concrete Inspired by Human Bone

Engineers at Princeton University have created a new, resistant cement material inspired by the tough outer layer of human bones.

The bio-inspired design, which the engineers at Princeton state is 5.6 times more damage-resistant than standard cement, allows the material to resist cracking and sudden failure.

The research team was led by assistant professor of civil and environmental engineering, Reza Moini, and third-year Ph.D. candidate, Shashank Gupta. Funding for the project was provided by the National Science Foundation CAREER Award, and the CMMI Division Grant.

The team released an article of their findings, entitled “Tough Cortical Bone-Inspired Tubular Architected Cement-Based Material with Disorder,” in Advanced Materials on 10th September 2024.

They found that cement paste, when deployed with a tube-like architecture, significantly increased resistance to crack propagation, and improved the ability to deform without sudden failure.

“One of the challenges in engineering brittle construction materials is that they fail in an abrupt, catastrophic fashion,” Gupta said in a statement.

The proposed technique tackles the main problems of existing construction materials used in building and civil infrastructure by creating a material that is tougher than conventional materials, while maintaining strength.

The improvement lies within the purposeful design of the internal architecture, balancing the stresses at the crack front with the overall mechanical response.

“We use theoretical principles of fracture mechanics and statistical mechanics to improve materials’ fundamental properties ‘by design’,” said Moini.

The team drew inspiration from the dense outer shell of the human femur, known as the cortical bone. This bone consists of elliptical tubular components, known as osteons, embedded weakly in an organic matrix.

The unique architecture of the bone deflects cracks around osteons, which prevents abrupt failure, provides strength and resists crack propagation.

The team took this innovative approach and incorporated it into their design, which includes cylindrical and elliptical tubes within the cement paste to interact with propagating cracks.

“One expects the material to become less resistant to cracking when hollow tubes are incorporated,” said Moini. “We learned that by taking advantage of the tube geometry, size, shape, and orientation, we can promote crack-tube interaction to enhance one property without sacrificing another”.

During their research, the team learned that the enhanced crack-tube interaction initiates a stepwise toughening mechanism. The crack is trapped by the tube, then delayed from propagation, which in turn leads to additional energy dissipation at every step.

“What makes this stepwise mechanism unique is that each crack extension is controlled, preventing sudden, catastrophic failure,” said Gupta. “Instead of breaking all at once, the material withstands progressive damage, making it much tougher”.

The research team’s approach lies within the geometric design of the material, manipulating the structure of the material itself to achieve significant improvements in toughness, without the need for additional material.

“We’ve only begun to explore the possibilities,” said Gupta. “There are many variables to investigate, such as applying the degree of disorder to the size, shape, and orientation of the tubes in the material. These principles could be applied to other brittle materials to engineer more damage-resistant structures”.

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