Bourns Hall

Colloquium

Nancy R. Sottos Department of Theoretical and Applied Mechanics & The Beckman Institute for Advanced Science and Technology University of Illinois at Urbana-Champaign www.tam.uiuc.edu/faculty/sottos Mechanics of Self-Healing Materials Systems Abstract Inspired by biological systems in which damage triggers an autonomic healing response, structural polymeric materials have been developed that possess the ability to self-heal. This seminar focuses on fracture mechanics issues consequential to the development and optimization of this new class of materials. First generation self-healing composites incorporate a microencapsulated healing agent and a transition metal catalyst within a polymer matrix. When cracks develop, the microcapsules rupture and release healing agent into the damaged region through capillary action. As healing agent contacts the embedded catalyst, polymerization is initiated which then bonds the crack face closed. Healing efficiency is assessed through fracture tests performed on the virgin material and on the material after healing. Once healed, the self-healing polymer can recover over 90% of its virgin fracture toughness. More recent investigations under cyclic loading demonstrate the ability to extend the fatigue life by several orders of magnitude through self-healing. Although high healing efficiencies have been achieved using this concept, only a limited supply of healing agent is available in the microcapsules. A second generation of self-healing composites has been developed that utilize an interconnected microvascular network to flow healing agent into the crack plane. This concept is applied to heal a brittle coating on a substrate containing a microvascular network. The results from the microvascular system are compared with appropriate controls as well as healing efficiencies of a microcapsule system. Integration challenges, material limitations and new self-healing concepts will also be discussed. Biosketch Nancy Sottos is a full professor and interim head of the Department of Theoretical and Applied Mechanics, a faculty affiliate and co-chair of the Molecular and Electronic Nanostructures Research Thrust at the Beckman Institute for Advanced Science and Technology and a designated University Scholar at the University of Illinois at Urbana-Champaign. Her research group studies the mechanics of complex, heterogeneous materials such as advanced composites, thin film devices, and microelectronic packaging, specializing in meso-scale characterization of deformation and failure in these material systems. Current research focuses on the development of autonomic materials systems that have the ability to achieve adaptation and response in an independent and autonomic fashion (e.g., recent work on autonomic healing in polymers). Research and teaching awards include the Office of Naval Research Young Investigator Award (1992), Outstanding Engineering Advisor Award (1992, 1998, 1999 and 2002), the Robert E. Miller award for Excellence in Teaching (1999), the University of Delaware Presidential Citation for Outstanding Achievement (2002), and the Hetényi Award from the Society for Experimental Mechanics (2004). Her research group was awarded the American Society for Composites Best Paper Award in 2002 and 2003 and the Tech Museum of Innovation Award for Technology Benefiting Humanity in 2001 for work on self-healing polymers. She is currently serving as the Senior Technical Editor for the journal, Experimental Mechanics and is on the editorial board for Composites Science and Technology. She is also the faculty advisor for the student chapter of the Society of Women Engineers. Wednesday, April 6, 2005 Bourns Hall A265 10:10 a.m.-11:00 a.m. (Refreshments will be served at 10:00 a.m.)