CANCELLED: Title: Rethink Wood: Its Unconventional Applications in Advanced Material Design
Speaker: Teng Li, Department of Mechanical Engineering, University of Maryland
Date: WILL BE RESCHEDULED
Location: NASA/LaRC, Building 1293A, Room 222
Abstract: There exist surging societal needs for products made from renewable and sustainable resources that are biodegradable, carbon neutral and non-petroleum based. Wood cellulose fibers, the major components of paper, are obtained from plants and represent one of the most abundant and renewable materials on earth. Wood cellulose fibers have an intrinsically hierarchical structure, which holds promises to enable an array of highly desirable properties and thus could enable unconventional applications beyond their traditional use. In this talk, Teng Li will show case an unconventional application of wood cellulose fibers: An anomalous scaling law of strength and toughness of cellulose nanopaper. The quest for both strength and toughness is perpetual in advanced material design; unfortunately, these two mechanical properties are generally mutually exclusive. A general mechanism to address the conflict between strength and toughness still remains elusive. Teng Li reports a first-of-its-kind study of the dependence of strength and toughness of cellulose nanopaper on the size of the constituent cellulose fibers. Surprisingly, we find that both the strength and toughness of cellulose nanopaper increase simultaneously (40 and 130 times, respectively) as the size of the constituent cellulose fibers decreases (from a mean diameter of 27 μm to 11 nm), revealing an anomalous but highly desirable scaling law of the mechanical properties of cellulose nanopaper: the smaller, the stronger and the tougher. The findings of this research could lead to a new class of high performance nanocomposite materials that are both strong and tough, a Holy Grail in materials design. To this end, we have demonstrated high performance fibers by hybridizing nano cellulose fibers and graphene oxide.
Biography: Teng Li is currently an Associate Professor of Mechanical Engineering and the Keystone Professor in the Clark School of Engineering at the University of Maryland, College Park, and the Associate Distinguished Langley Professor at the National Institute for Aerospace. He is also an affiliated faculty of Maryland Nano Center and University of Maryland Energy Research Center. He received his Ph.D. degree in Engineering Science from Harvard University in 2006, following earlier studies at Princeton University and Tsinghua University. His research interests include mechanics of sustainable materials, mechanics of flexible electronics and Nano electronics, mechanics of low dimensional carbon nanomaterials, mechanics of soft materials and biomaterials, and mechanics in energy systems. He has published 80+ journal papers, including in top journals such as Science, Nature, PNAS, Physical Review Letters, etc. His publications have been cited 4400+ times, with an h-index of 30. Four of his journal publications are Web of Science Highly Cited Papers (with enough citations to place it in the top 1% of its academic field). Among his awards includes Society of Engineering Science (SES) Young Investigator Medal in 2016, RASA Research Award in 2014, US National Committee of Theoretical and Applied Mechanics Fellowship in 2012, E. Robert Kent Outstanding Teaching Award in 2012, Ralph E. Powe Jr. Faculty Award in 2007. He has been a member of the Technical Committee of Integrated Structures in ASME Applied Mechanics Division since 2006 and served as the Chair of the Committee during 2008-2012. He currently serves as the Associate Editor of Extreme Mechanics Letters and a member of the Editorial Board of International Journal of Computational Materials Science and Engineering. With Zhigang Suo, he co-founded iMechanica.org, the world’s largest online community of mechanics with tens of thousand of registered users from all over the globe.