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
o
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.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-3008 |
| Date | 15 May 2009 |
| Creators | Muddasani, Maithri |
| Contributors | Muliana, Anastasia |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | electronic, application/pdf, born digital |
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