Engineers at Princeton have developed a cement-based material inspired by the architecture of human bone that is significantly more damage-resistant than standard counterparts. The material, designed with a tube-like architecture, can resist cracking and avoid sudden failure, unlike traditional brittle cement-based materials. This innovative design increases resistance to crack propagation, improves the ability to deform without sudden failure, and enhances overall toughness while maintaining strength. The team, led by Reza Moini and Shashank Gupta, utilized theoretical principles of fracture mechanics and statistical mechanics to purposefully design the internal architecture and balance stresses at the crack front with the overall mechanical response.
Taking inspiration from human cortical bone, which consists of elliptical tubular components known as osteons, the researchers incorporated cylindrical and elliptical tubes within the cement paste to interact with propagating cracks. Contrary to expectations, the inclusion of hollow tubes did not weaken the material, but instead promoted crack-tube interaction and enhanced toughness. The team observed a stepwise toughening mechanism where cracks were trapped and delayed from propagating, leading to additional energy dissipation at each interaction. This unique mechanism controls crack extension and prevents sudden, catastrophic failure, making the material much tougher than traditional cement-based materials strengthened with fibers or plastics.
In addition to improving fracture toughness, the researchers introduced a new method to quantify the degree of disorder in architected materials. By using statistical mechanics, the team established parameters to quantify the degree of disorder in the material’s architecture, providing a more accurate representation of the arrangements. This framework moves beyond simple binary classifications of periodic and non-periodic structures to reflect a spectrum from ordered to random. By incorporating advanced fabrication methods such as additive manufacturing, the researchers can further explore disordered and mechanically favorable structures, scaling up the tubular designs for civil infrastructure components with concrete.
The new framework developed by the team offers a powerful tool to describe and design materials with a tailored degree of disorder, distinguishing from approaches that confuse irregularity and perturbation with statistical disorder. By applying this approach to other brittle materials, the researchers aim to engineer more damage-resistant structures with improved mechanical properties. With techniques allowing for precision using robotics and additive manufacturing, the team hopes to explore new architectures and combinations of hard or soft materials within the tubes to expand the possibilities of applications in construction materials. There are many variables to investigate, such as applying the degree of disorder to the size, shape, and orientation of the tubes, promising a wide range of applications in the field of engineering and construction.