From glass windows to eyeglasses to lenses in telescopes, new developments in glass science have been key enablers for modern civilization throughout history. This societal impact has not diminished as humans physically interact with inorganic glass surfaces now more than ever—for instance, the use of glasses for LCD/OLED panels and damage-resistant protective covers has transformed the way in which humans interact with modern computing devices. However, the risk of scratch-induced damage in glasses remains a key concern, which seriously limits glass’s suitability for many applications. Scratch-induced damage can occur at various stages of a glass’s lifecycle, e.g., sheet production, packaging, transport, and service life. For all these reasons, the development of novel glasses exhibiting improved resistance to scratch-induced damage would be key to extending the range of applications of this material. To address this concern, this project interrogated the physics governing the indentation and scratching of glasses by exploring the nature and origin of the energy dissipation mechanisms that are at play within a glass subjected to load—to provide a science-based foundation to develop new glasses with improved resistance to scratching.

As a first key outcome, we developed a new modeling method to reveal the atomic structure of glasses. By “inverting” experimental data obtained by diffraction into three-dimensional glass structures, this approach offers for the first time an accurate description of the disordered atomic structure of silicate glasses. This is significant since conventional experiments can only offer some indirect “signatures” (or “fingerprints”) of the atomic structure of glasses (e.g., average bond length, average coordination number, etc.). These new structural insights are key to decoding how the atomic structure of glasses governs their mechanical properties.

Second, our continuum-level simulations established peridynamics as a promising method to accurately simulate the mechanical response of oxide glasses upon indentation and scratching. Peridynamics simulations revealed some details (e.g., stress field, activated elastic volume size, individual contribution of elastic and inelastic deformation, etc.) that are otherwise challenging to access experimentally. This knowledge allowed us to decipher the underlying physics governing the response of glasses to indentation and scratching.

Finally, by conducting a detailed forensic investigation of the atomic-scale mechanisms governing the behavior of glasses subjected to indentation and scratching, we isolated and quantified the various energy dissipation mechanisms acting in the glass when subjected to loads (e.g., shear flow, permanent densification, and cracking). Importantly, we explored how these mechanisms are impacted by the geometry and stiffness of the indenter tip. Isolating the various mechanisms at play during scratching allowed us to investigate their distinct structural mechanisms and origins.

All these insights allowed us to discover new glasses with enhanced mechanical behaviors in a rational fashion—by “nanoengineering” their atomic structure. Such glasses could expand the range of applications of glass, which is often limited by its susceptibility to damage. For instance, such glasses can improve the efficiency of energy conversion in photovoltaic solar panels and help enable the next generation of strong, lightweight, and energy-efficient architecture. In a world where humans now primarily interact with electronic devices through a piece of glass, the discovery of damage-resistant glasses could revolutionize the glass industry.

This project trained two Ph.D. students (including one female student), four master students (including two female students), and four undergraduate students (including three female students). Students received several major awards and had the opportunity to present the outcomes of their research at international conferences. All the students were regularly interacting with research scientists from industry partners. This contributed to exposing them to an industrial research and development environment, which is key for the development of the future workforce that the U.S. industry needs. Several new classes, short-courses, and online video tutorials were developed within the scope of this award. Finally, through a series of events and courses, this award has supported the 2022 International Year of Glass declared by the United Nations General Assembly to celebrate the heritage and importance of this material in our lives.

Last Modified: 12/25/2022
Modified by: Mathieu Bauchy