Earthquake prediction techniques lend quick insight into strength, reliability of materials

The new study, led by the University of Illinois Urbana-Champaign in collaboration with Sandia National Laboratories and Bucknell University, shows that the amount of deformation caused by stress applied locally to the surface of muscovite mica is controlled by the physical condition of the mineral's surface and follows the same statistical dynamics observed in earthquakes and avalanches.

The study findings are published in the journal Nature Communications.

When selecting materials for engineering applications, scientists want to know how the surface of that material will interact with the environment in which it will be used. Similarly, geologists want to understand how chemical reactions between minerals and groundwater along faults might slowly weaken rocks and result in quick bursts of mechanical failure due to a process called chemomechanical weakening.

"While previous attempts to quantify the effect of chemomechanical weakening in engineered materials have relied on complex molecular dynamics models requiring significant computational resources, our work instead emphasizes the bridge between laboratory experiments and real-world phenomena like earthquakes," said graduate student Jordan Sickle, who led the study with Illinois physics professor Karin Dahmen.

"Muscovite was chosen for this study mainly because of this material's extreme flatness," Dahmen said. "Each of its flaky layers is flat down to the atomic level. Because of this flatness, the interaction between the surface of this material and its environment is especially important."

To measure chemomechanical weakening on muscovite surfaces, Sandia National Laboratories exposed samples to different chemical conditions -- dry, submersed in deionized water and in salt solutions with a pH of 9.8 and 12. During exposure, an instrument known as a nanoindenter poked the surface of the minerals and recorded the displacements, or failures, in the material at controlled mechanical loads.

The researchers found that in dry conditions, muscovite can deform more before it fails than in wet conditions. At failure, the samples in each condition release their stored elastic energy. The study reports that when muscovite is exposed to a basic solution at pH 9.8 or 12, the top layer weakens, and less energy can be stored before failure occurs, which is reflected in the burst statistics.

"The results of this work allow researchers to test material failure more quickly than high-powered, detailed simulation models," Sickle said. "By showing that we can observe the same results by using the statistical models already in place for earthquakes, researchers will be able to perform higher-throughput material analysis than previously possible."

The U.S. Department of Energy and Sandia National Laboratories support this research.