Abstract:  Layered polymer matrix nanocomposites are manufactured in our laboratory with nanoscale structural control via the layer-by-layer (LBL) assembly process. These unique multi-layered materials are of interest in a wide variety of applications including transparent blast and ballistics resistant materials. In this talk I will discuss our use of polyurethane (PU), polyacrylic acid (PAA) and montmorillonite clay (MTM) components to manufacture multi-layered PU/PAA, PU/MTM and PU/PAA/MTM nanocomposite films. Constitutive models of the mechanics of these nanocomposites are developed. In PU/MTM nanocomposites, the PU matrix in the vicinity of the MTM nanoparticles is modified leading to an interphase region, and its effect on the finite deformation response is treated by considering the layered nanocomposites as comprised of layers of bulk polymer and effective particles with amplified strain. This model is shown to predict the effect of increased MTM volume fraction on the non-linear strain hardening response. The elastic response of PU/MTM nanocomposites is examined in detail using i) a finite element analysis that includes an interphase region, ii) a modified hierarchical, multi-layered interphase model and iii) a size-dependent strain gradient Mori-Tanaka method. The effects of particle size, particle to matrix stiffness ratio and particle shape on the composite response are examined. Next we consider the ability to design polymer nanocomposites for simultaneous high stiffness and high damping characteristics and a non-linear constitutive model capable of predicting stiffness and damping is developed. Time permitting, other topics such as toughening mechanisms in PU/PAA nanocomposites, tailoring interfaces in PU/PAA/MTM nanocomposites and other nanostructures and materials will be discussed. 

Bio:  Prof. Arruda received her PhD from MIT in 1992. Her research focuses on the mechanical behavior of materials including polymers, elastomers and soft tissue, tissue engineering of tendon and muscle constructs, constitutive modeling of growth, remodeling and functional adaptation in soft tissue, deformation mechanisms in polymers, crystal transformation mechanisms in semi-crystalline polymers, and split Hopkinson pressure bar testing of polymers and elastomers for high strain rate applications including crashworthiness in automotive applications. She holds appointments at UMich in the Mechanical Engineering, and Macromolecular Science and Engineering Departments. Prof. Arruda is a recipient of the NSF CAREER Award and is a Fellow of ASME, the Society of Engineering Science, and the American Academy of Mechanics.

Host:  Prof. Matthew Begley begley@engr.ucsb.edu