Application of a nonlinear viscoelastic model to the design of polymeric structures /
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| Other Authors: | , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1991.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | In the bulk, the nonlinear viscoelastic response of glassy polymers is due to the irreversible work done on the body by the surroundings. The source of the irreversibility is the plastic flow of material near distributed shear bands or microcracks distributed throughout the polymer. These changes in polymer lattice structure are a mechanism that promotes the release of stored strain energy. It will be seen that for polycarbonate the total work during proportional loading is approximately independent of the hydrostatic component of stress for σ < σ[y]. While the constitutive modeling of polycarbonate showed little dependence on the hydrostatic pressure below yield, dynamic mechanical spectra at T = T[y] on prestressed and unstressed specimens of polycarbonate showed evidence that stress serves to increase the free volume of the polymer. For an isolated flaw in material of sufficient size, the nonlinear viscoelastic response is due to the decrease in the free energy per unit extension of the crack. It is hypothesized that the presence of a small inelastic zone ahead of a crack embedded in a large linear viscoelastic body, enables the use of linear viscoelasticity theory to model the mechanical behavior of this glassy body. Here, Schapery's correspondence principle II (CP II) was applied to a fracture specimen to eliminate the time dependence due to linear viscoelasticity. This may be useful in the construction of a time independent J-R curve for the fracture of ductile polymer that exhibit slow stable crack growth. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Interdisciplinary Engineering." |
| Physical Description: | xii, 150 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |