More than 350 million metric tons of plastic waste are generated globally each year, with less than 9% being recycled, creating both a major environmental burden and a large loss of material value. Major companies from Amazon to Coca-Cola to Procter & Gamble are pushing to reduce virgin plastic use and increase circularity, yet recycled polymers cannot be used in demanding applications. They inherit degradation, contamination, and morphological heterogeneity from their previous life leading to poorly controlled stiffness, strength, and fracture resistance. Closing the plastic loop therefore requires addressing several challenges which are connected to fundamental mechanics questions: Can variability in recyclates be suppressed through design? Can failure under realistic service conditions be predicted efficiently? And do the fracture criteria we use adequately describe these polymer systems?

In this talk, I will describe a nacre-inspired hard-soft architecture and an uncertainty-aware tension-shear-chain model showing how interfacial load transfer can suppress the propagation of constituent-level variability into stiffness and failure. I will also introduce a high-throughput photoelastic testing platform that resolves stress localization and fracture in recycled thermoplastics under coupled chemical and mechanical loading, capturing ductile-to-brittle transitions and degradation mechanisms under realistic environments while enabling data-efficient service-life prediction. Finally, I will show how these studies motivate fundamental questions in nonlinear fracture mechanics, including whether stable crack growth in thermoplastic sheets is governed by a material-specific, constant crack-tip opening angle.

Together, these advances provide new tools for understanding, predicting, and improving the mechanical performance of recycled polymers, supporting their broader adoption in engineering applications.

Bio: 

Prof. Christos Athanasiou is a mechanician and physicist focusing on materials whose growing importance to a circular and resource-efficient economy has outpaced our understanding of how they deform and fail. His group develops advanced experiments and physically interpretable models to reveal the fundamental mechanics of these materials and translate this new knowledge into design strategies for reliable, resource-efficient, and sustainable systems. He is an Assistant Professor in the Daniel Guggenheim School of Aerospace Engineering at the Georgia Institute of Technology. Before launching his independent career, he conducted postdoctoral research at Brown University and the MIT Media Lab and received his Ph.D. in Photonics from EPFL in Switzerland. Prof. Athanasiou has been recognized with the NSF CAREER Award, the ASME Orr Early Career Award, the ASME Eshelby Mechanics Award for Young Faculty, and a Climate Tech Fellowship from the The New York Climate Exchange supporting the translation and commercialization of his research.