For Dr. Shailendra P. Joshi, the Bill D. Cook Assistant Professor of Mechanical Engineering at the University of Houston's Cullen College of Engineering, as the technological advances in the world of plastics as structural materials have occurred, there has been the negative side effect of the environmental impact of those materials.
“The ubiquity of plastics, both thermoplastics and thermosets, in our daily lives presents challenges due to their potential threats to the environment and natural habitats arising from their low recyclability,” he said. “Conventional thermoset polymers, whose attractive mechanical properties make them important structural materials, are particularly insidious. The irreversible crosslinking at the molecular level seriously impedes their reprocessing and recycling ability. Novel polymer chemistries offer exciting avenues to develop recyclable thermosets, which are also known as vitrimers."
However, understanding the mechanical behaviors of reprocessed vitrimers is challenging. Joshi hopes to change that by examining these materials at multiple length-scales, starting at a granular level. “Each recycling and reprocessing cycle of a preceding vitrimer part, via pulverization and compaction, generates defects in the recycled part, which redefines its microstructure and hence, the mechanical properties. We aim to fundamentally understand the microstructure-property linkages of such vitrimers using novel theoretical approaches and computational tools.” He is the latest recipient of a National Science Foundation CAREER award, one of the most prestigious grants in support of early-career faculty. They are given out annually to professors who have the potential to serve as academic role models in research and education, and to lead advances in the mission of their department or organization.
He added, “The scientific challenge is rooted in unraveling the damage processes associated with the statistics of microscale defect structures resulting from the coupling between the chemistry and the mechanics of the vitrimers. Its technological relevance is rooted in the need for a predictive modeling and simulation framework to enable damage-tolerant vitrimers for structural applications.”
“I was happy, elated and humbled,” he said of receiving the award. “There is a long list of people who have helped shape my academic path, including my mentors. I particularly appreciate the support of Professor Pradeep Sharma, the Mechanical Engineering Department Chairman, who made my transition to the U.S. three years ago comfortable, and my department colleagues, for a stimulating and collegial environment. My family has been a strong positive force all along, but most critically during the past three years here in Houston, as I pretty much reset my academic career.”
Joshi said that receiving the CAREER award, which comes with $516,654 in funding, will allow him to pursue granular mechanics. In addition to the NSF, he has also received funding from the U.S. Army Research Lab through the Materials in Extreme Dynamic Environments (MEDE) Program.
“I am broadly interested in failure of materials,” he said. “Our current research focuses on understanding the mechanics of damage in advanced metallic materials, such as magnesium alloys, which are perhaps the lightest structural metals, nearly 60 percent lighter than aluminum for the same material volume, using computational approaches.”
Joshi described the research that the CAREER award would enable the design and development of recyclable structural plastics, which could help mitigate better the harmful environmental effects of conventional plastics.
He noted, “The research program is integrated into a broader educational goal of creating an immersive learning experience for underrepresented student groups, including students with disabilities, an integration of granular art in education grades K-12, and development of a graduate course on the microstructure-sensitive failure of materials.”