Nair, Aravind R. (2006-08). Characterization of thermo-mechanical and long-term behaviors of multi-layered composite materials. Master's Thesis. Thesis uri icon


  • This study presents characterization of thermo-mechanical viscoelastic and long-term
    behaviors of thick-section multi-layered fiber reinforced polymer composite materials.
    The studied multi-layered systems belong to a class of thermo-rheologically complex
    materials, in which both stress and temperature affect the time-dependent material
    response. The multi-layered composites consist of alternating layers of unidirectional
    fiber (roving) and randomly oriented continuous filament mat. Isothermal creep-recovery
    tests at various stresses and temperatures are performed on E-glass/vinylester and Eglass/
    polyester off-axis specimens. Analytical representation of a nonlinear single
    integral equation is applied to model the thermo-mechanical viscoelastic responses for
    each off-axis specimen. Long-term material behaviors are then obtained through vertical
    and horizontal time shifting using analytical and graphical shifting procedures. Linear
    extrapolation of transient creep compliance is used to extend the material responses for
    longer times. The extended long-term creep strains of the uniaxial E-glass/vinylester
    specimens are verified with the long-term experimental data of Scott and Zureick (1998).
    A sensitivity analyses is then conducted to examine the impact of error in material
    parameter characterizations to the overall long-term material behaviors. Finally, the
    calibrated long-term material parameters are used to study the long-term behavior of
    multi-layered composite structures. For this purpose, an integrated micromechanical
    material and finite element structural analyses is employed. Previously developed
    viscoelastic micromodels of multi-layered composites are used to generate the effective
    nonlinear viscoelastic responses of the studied composite systems and then implemented
    as a material subroutine in Abaqus finite element code. Several long-term composite
    structures are analyzed, that is; I-shaped columns and flat panels under axial compression, and a sandwich beam under the point bending and transmission tower under
    lateral forces. It is shown that the integrated micromechanical-finite element model is
    capable of predicting the long-term behavior of the multilayered composite structures.

publication date

  • August 2006