Muddasani, Maithri (2008-08). Nonlinear viscoelastic behaviors of multilayered (pultruded) composites at various temperatures and stresses. Master's Thesis. Thesis uri icon


  • This study presents experimental works and finite element (FE) analyses for
    understanding nonlinear thermo-viscoelastic behaviors of multilayered (pultruded)
    composites under tension. Uniaxial isothermal creep tests in tension are conducted on Eglass/
    Polyester pultruded composites of 0o, 45o and 90o off-axis fiber orientations subject
    to combined temperatures and stresses. The temperatures range from 0?F to 125?F, and
    stress levels range from 20% to 60% of the ultimate tensile strength of the composite
    specimen. The creep responses seem to accelerate with temperature for higher
    temperatures (75oF to 125oF) and do not behave in any particular manner for lower
    temperatures (0oF to 50oF). Isochronous curves of time-dependent material responses
    show that the nonlinearity increases with time and also temperature for higher
    temperatures while there is no particular trend seen at lower temperatures. Also, the
    creep responses of the axial specimens show negligible nonlinearity when compared to
    that of the transverse and 45o off-axis specimens. The Poisson's effect is studied and
    orthotropic material symmetry conditions are satisfied. A nonlinear viscoelastic
    constitutive model, based on convolution integral equation, is presented for orthotropic materials. The nonlinear stress-temperature-dependent material parameters are coupled
    in the product form and are calibrated using the experimental data. Overall good
    predictions are shown but for a slight mismatch in the prediction of the responses at
    temperatures below 50
    F owing to the random behavior of the creep responses at lower
    temperatures. The numerical integration algorithm for the nonlinear viscoelastic model
    of orthotropic composite materials developed by Sawant and Muliana (2008) was used
    to integrate the constitutive material model to FE structural analyses. Sensitivity analysis
    is conducted to check for error in experiments by numerically simulating the testing
    procedure. A practical structural analysis is carried out on composite slabs using
    ABAQUS and our model is used to predict the responses of slabs under combined stress
    and temperature loading.

publication date

  • August 2008