Four years ago, the challenge NASA set before Ramathasan Thevamaran was—to put it lightly—considerable. As part of its 2022 Early Career Faculty awards, the agency solicited proposals to create composite materials capable of maintaining exceptional dimensional stability amid the extreme temperature changes encountered in space.
Just how stable?
The current state-of-the-art standard for such materials in terms of coefficient of thermal expansion (the value of how much their size changes in response to temperature variance) is measured in parts per million per Kelvin—meaning a 1-meter rod could expand or contract by 1 micron (one-millionth of a meter) for every degree change.
In contrast, NASA’s charge to researchers was to devise materials that could hold their shape when measured in parts per billion per Kelvin.
Oh, and the material also needed to be stiffer than stainless steel.
“This is an exceptionally challenging problem,” says Thevamaran, the Bernard A. and Frances M. Weideman Associate Professor of mechanical engineering at the University of Wisconsin-Madison.
Over the past four years, Thevamaran’s research group has worked steadily toward that goal, with the first step being designing such a material. To do that, though, the team needed to develop a framework for design and fabrication, which it published in a paper in the journal Composites Part B: Engineering. The paper, with postdoctoral research associate Yasara Dharmadasa and PhD student Paranjoy Basak as joint first authors, is the first in a series that Thevamaran’s group will publish to demonstrate its progress on the project.
Ultra-stable materials are necessary for projects such as NASA’s planned Habitable Worlds Observatory, a powerful telescope that will search for signs of life in deep space, building upon the work of the James Webb Space Telescope.
Thevamaran’s team is focused on fiber-reinforced composite materials. The framework that Dharmadasa, Basak and Thevamaran developed, which they’re sharing online as an open source, allows them to rapidly screen fiber-matrix combinations and then take into account variability in both material properties and manufacturing quality of constituents.
Using their framework, they learned that, fortuitously, greater stiffness (or, larger modulus of elasticity) and near-zero coefficient of thermal expansion were synergistic rather than competing aims; greater stiffness helps reduce variability in the coefficient of thermal expansion.
“We now have a way to identify promising constituent material combinations and understand how sensitive the coefficient of thermal expansion and the modulus of the composite are to real-world variability in the constituents and manufacturing parameters,” says Dharmadasa, who completed his PhD in aerospace engineering sciences at the University of Colorado Boulder, “and now we are going into the prototype fabrication and testing to determine the modulus and the coefficient of thermal expansion.”
In order to adequately test their prototypes, they had to build custom instrumentation such as an interferometer to measure material deformation near the picometer scale. Very few such devices exist around the world, Thevamaran notes.
Dharmadasa will present the group’s work at the American Society for Composites’ annual technical conference in late September 2026 at UW-Madison, as well as the Society of Engineering Science’s annual technical meeting in October at Purdue University.
Top photo caption: From left, postdoctoral research associate Yasara Dharmadasa, Associate Professor Ramathasan Thevamaran and PhD student Paranjoy Basak demonstrate their material testing setup. Photo: Tom Ziemer