A study of plastic flow and thermal aging on the response of glassy polycarbonate with an emphasis on characterization and modeling of the development of elastic anisotropy, and of anisotropic toughening
发布时间: 2012-08-06 08:09:00
报告题目：A study of plastic flow and thermal aging on the response of glassy polycarbonate with an emphasis on characterization and modeling of the development of elastic anisotropy, and of anisotropic toughening
报告人：Mehrdad Negahban
主持人：励争 教授
内容摘要：There is a substantial change in the anisotropy of some glassy polymers when they are subjected to large plastic deformations. The most pronounced case is probably seen in polycarbonate (PC), which is a tough thermoplastic used for many structural applications, including its use as protective transparent armor for such applications as bulletproof glass. The scale of the change in anisotropy is in the same order as the induced plastic strain, and reflects itself in practically all aspects of the materials response including its wave speed, fracture energy, fracture mode, and thermal conductivity. Typically, this changed takes an initially isotropic material into a highly anisotropic one. This feature, that is highly pronounced, is totally ignored in modeling these polymers, a fact that can result in substantial error in simulations. In addition, thermal aging can have a substantial influence on these plastic flow induced anisotropic characteristics.
The presentation will cover many of these issues in addition to show how current models can be modified to capture the development of anisotropy in the wave speeds.
Mehrdad Negahban is a Professor of Engineering Mechanics at the University of Nebraska-Lincoln specializing in the characterization and modeling of large deformation thermodynamic response of materials and their numerical simulation. He graduated with a B.S. in Mechanical Engineering from Iowa State University of Science and Technology, and an M.S. and Ph.D. in Applied Mechanics from the University of Michigan. His research has focused on continuum mechanics and thermodynamics of solids, constitutive theory, characterization and modeling of glassy polymers and crystallizing polymers, finite deformation plasticity, numerical simulation at large deformations, and finite elements for generalized shells. A current area of interest is the mechanics of soft tissue under dynamic loading and the use of stereo optical measurement methods for three-dimensional characterization of deformation. (mnegahban（at）unl.edu)