Brown University School of Engineering

Engineering Seminar: Joint Materials/Solid Mechanics Seminar Series

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Monday, September 18, 2017 4:00pm - 5:00pm

Dr. Shawn A. Chester, Asst. Professor of Mechanical Engineering, New Jersey Institute of Technology will present a talk: "Multiphysics Mechanics of Polymeric Materials." Abstract: Many new and exciting phenomena in mechanics are inherently multiphysics. A few examples include thermally responsive shape-memory polymers, Joule heating causing creep, and pore pressure effects in geo-materials to name just a few. Because so many technologically important phenomena are inherently multiphysics, constitutive models and associated simulation tools must also include all relevant physics to capture the primary features of the materials response to be predictive. In this talk, I will discuss recent and ongoing research on the multiphysics response of polymeric materials, specifically on polymer gels and light active shape memory polymers. A gel is a polymeric material swollen by a fluid. The fluid does not degrade or chemically modify the polymer network. The talk begins with a brief review of a model for the coupled deformation-diffusion of gels. That is followed by some recent attempts for experimental calibration and validation (or lack thereof) on relatively simple gels. Preliminary results have shown that the majority of existing constitutive models are not capable of capturing the observed behavior. Next, the talk changes gears and moves onto the topic of light-activated shape-memory polymers. The underlying mechanism that controls the shape memory effect in these materials is a photochemical reaction driven by light. That reaction may form or cleave bonds between functional groups attached to the polymer backbone, causing crosslinks to form or dissolve, modifying the underlying network structure. A model is proposed and a numerical capability described that qualitatively describe the behavior of these materials. Bio: Shawn Chester is currently an assistant professor in the Mechanical and Industrial Engineering Department at the New Jersey Institute of Technology. Shawn was previously a postdoctoral researcher at Lawrence Livermore National Laboratory and currently still holds a visiting appointment there. Prior to that he obtained his PhD in solid mechanics from the Mechanical Engineering Department at MIT, and obtained both his BS and MS in Mechanical Engineering from NJIT. Shawn's research focus in the past few years has been the development of experimentally validated continuum level constitutive theories for large-deformation multi-physics behavior of polymeric materials and the associated numerical implementation. His work spans most aspects of mechanics; experimental characterization, theoretical modeling, numerical implementation, and experimental validation.