Materials like car tires, human tissue, and spider webs, while varying in composition, are all made up of networks of interconnected fibers. A long-standing question about the strength of these materials is: “How much energy would it take to break these diverse networks?” A newly published paper from MIT researchers offers new insights.
“Our results reveal a simple general law governing the fracture energy of networks across a range of materials and length scales,” says Shuanghe Zhao, the Uncas and Helen Whitaker Professor of Mechanical Engineering and Civil and Environmental Engineering at MIT. “This discovery has important implications for the design of new materials, structures, and metamaterials, enabling the creation of extremely strong, soft, and stretchable systems.”
While there is some understanding of the importance of fault tolerance in the design of such networks, until now there has been no physical model that effectively couples fiber mechanics and connectivity to predict block failure. This new work uncovers universal scaling laws that bridge length scales and help predict the intrinsic fracture energy of diverse networks.
“This theory helps us predict how much energy it would take to create cracks and break these networks,” said graduate student Chase Hartquist, one of the paper’s lead authors. “Now we know we can engineer stronger versions of these materials by making the fibers longer, more elastic, or by increasing the force required to break.”
To validate their results, the team 3D printed giant, stretchy meshes to demonstrate real-world fracture properties. They found that despite differences in the networks, all followed simple, predictable patterns. In addition to modifying the fibers themselves, they could also strengthen the mesh by connecting the fibers into larger loops.
“By tweaking these properties, we can make tires more durable, tissue more resistant to damage, and spider webs more durable,” Hartquist says.
Xu Wang, a postdoctoral researcher in Zhao’s lab and co-first author of the paper, called the results “a very satisfying moment,” as it means the same rules can now be applied to describe many different types of materials, making it easier to design materials that are best suited for specific situations.
The researchers explain that the work marks an advancement in the emerging and exciting field of “architectural materials,” in which a material’s internal structure gives it its unique properties. The discovery sheds light on how to make these materials even tougher by focusing on engineering stronger, more resilient segments within their structure, the researchers say. The strategy is applicable to a wide range of materials and could be applied to improving the durability of soft robotic actuators, enhancing the strength of artificial tissues, and even creating elastic networks for aerospace technologies.
Their open access paper, “Scaling laws for the intrinsic fracture energy of variational elastic networks,” appears in Physical Review X, a leading journal of interdisciplinary physics
