A Rice University study will help scientists and engineers judge the ultimate strength, stiffness and toughness of composite materials for anything from nanoscale electronics to buildings. Rice researchers Rouzbeh Shahsavari and Navid Sakhavand have created universal maps that predict the properties of natural and biomimetic platelet-matrix composites (like nacre, aka mother-of-pearl) and synthetic stacks (or heterostructures) of materials like graphene and boron nitride.
They said their computer-drawn maps are “dimensionless” and their findings will work as well for materials built with nanoscale blocks as they would for a brick wall, or bigger. The formula relies on four characteristics of the individual materials under consideration for a composite: their length, a ratio based on their respective stiffness, their plasticity and how they overlap. “If you know [the inputs], you can predict the stiffness, strength and toughness of the final composite,” says Sakhavand, a graduate student at Rice. “We call this a universal map because all of those input parameters are relevant to all composites and their structural properties.”
The study began when Shahsavari, an assistant professor of civil and environmental engineering and of materials science and engineering, took a close look at the architecture of nacre, which maximizes both strength and toughness, properties that are typically mutually exclusive in engineered materials. Under a microscope, nacre looks like a well-built brick wall with overlapping platelets of different lengths held together by thin layers of an elastic biopolymer. However, engineering nacre-like composites has been difficult so far, “mainly because of the lack of a design map that can reveal the various links between the structure, materials and properties of nacre-like materials,” Shahsavari said.
The work is an important milestone toward a better ability to decode and replicate nacre’s architecture for lightweight, high-performance composites, which could benefit the aerospace, auto and construction industries. Their goal is to help engineers calculate the ultimate qualities of a material and cut down on trial and error.