Columbia University │ New York, New York
For transformative contributions to our understanding of the physical behavior of polymers, materials made of long chains of molecules, leading to innovative product development of rubber and other soft materials.
What happens when you stretch a rubber band? It gets longer and thinner, of course, but that’s only what we can see. The phenomena happening at the microlevel of the complex molecules that make up the rubber are what give it elasticity and stretchiness. For engineers using such materials, known as elastomers, understanding those phenomena is vital for deciding how best to create, structure, and use them in everything from automobiles to airplanes to sports equipment to medical devices. Mary Boyce’s work has not only provided new insights into the behavior of elastomers but also vital techniques for accurately modeling their behavior in the real world.
A brilliant and innovative engineer specializing in the mechanics of soft materials, Boyce is best known for the Arruda-Boyce model of the behavior of polymeric materials, first published by Boyce and her graduate student Ellen Arruda in 1993. Although previous models of the mechanics of elastic materials had existed for decades, they were limited in their usefulness, not quite able to predict the actual three-dimensional mechanical behavior of elastomers under real conditions of stress and strain. Her ingenious “8-chain” approach idealizes each point of the underlying molecular network of the material as a cube aligned with the material’s principal directions of stretch, with eight polymer chains extending from the center of the cube to the eight vertices. As the material deforms, the chains must extend and rotate at the molecular level to accommodate the macroscopic strain; the altered configuration results in stored energy that can be examined to evaluate the stress in the material. This model provides an actual physical representation of the material’s behavior with greater accuracy than any previously used, while requiring only two easily measured material attributes to create the model.
The Arruda-Boyce model was so useful and versatile that it quickly became adopted amongst mechanical and materials engineers for modeling soft polymeric mechanics in design and engineering applications. It also proved easily capable of extension into other areas involving polymers and other macromolecular networks, even including biology and medicine, where it’s been used to capture the behavior of soft biological tissues. Later, working with her graduate student J.S. Bergstrom, Boyce extended the Arruda-Boyce model to provide the foundation for a new method that included time-dependent behavior. Further, with H.J. Qi and later R. Rinaldi and H. Cho, she captured the complex cyclic loading behaviors of co-polymers. Co-polymers constitute molecular chains with backbones composed of more than one type of monomer, for example, polyurethanes. The initial 8-chain model had now been extended to predicting both elastic and dissipative energy characteristics of such resilient molecular networks. The time-dependent and cyclic softening models have been used to capture wide ranging nonlinear behaviors in synthetic products such as seals, protective coatings, tires, and sports equipment as well as further amplified to capture biological co-polymer materials including the energy dynamics of mussel byssal threads. Her Ph.D. students and postdocs continue to pioneer these and other developments in structuring soft polymers and composites in independent academic careers across the country and around the world.
Growing up in New Jersey, Mary Cunningham Boyce discovered her love and talent for mathematics in elementary school, a passion that continued throughout her primary schooling and first led her to consider becoming a physicist as she prepared for college. But she soon found herself fascinated by the practical nature of engineering, and majored in engineering mechanics at Virginia Tech. After graduation, she worked briefly in aeronautical engineering at Martin Marietta before deciding to concentrate on research and began her graduate studies at MIT. It was here, in an intense interdisciplinary environment, that she began her work in soft polymer mechanics and nonlinear elastic-viscoplastic behavior that culminated in her later discoveries. After earning her Ph.D., she began a 25-year career on the faculty of MIT, eventually rising to lead the Department of Mechanical Engineering.
In 2013, Boyce moved on to Columbia University, becoming dean of the Fu Foundation School of Engineering and Applied Science and then provost of the university from 2021 to 2023. As an educator, researcher, and administrator, she led major efforts in educational outreach and interdisciplinary research, expanding the visibility of engineering and its power as a pathway to impact humanity. She has mentored scores of students who will comprise the next generation of engineers. Boyce has also strongly advocated for the cross-disciplinary role of engineering as a foundational field that today can deeply affect and work with other disciplines.
Boyce’s contributions have been recognized with an impressive array of awards and honors. Early in her career, she was awarded the Presidential Young Investigator Award by the National Science Foundation. She is a fellow of the National Academy of Engineering, the American Academy of Arts and Sciences, the American Academy of Mechanics, and the American Society of Mechanical Engineers. Her work in the classroom and as a mentor has been honored with several prestigious teaching awards, including MIT’s highest teaching honor when she was named as a MacVicar Faculty Fellow. In 2020, she became the first woman to be awarded the Timoshenko Medal of the American Society of Mechanical Engineers.
At heart, whatever her other activities and accomplishments, Mary Boyce still considers herself to be an engineer and applied mechanician, driven by a deep curiosity about the workings of the physical world and a drive to understand, and to pass along that understanding to others. Whether it’s something as simple and common as a rubber band or a seal, as complex as a tire or a sneaker, or as futuristic as a soft robotic actuator, the work of Mary Boyce has given engineers vital insights and tools to better understand, design, and use materials.