A homogenization prediction of temperature-dependent effective thermoelastic properties and microscopic thermal stresses in high-temperature polymer composites
- Univ. of Houston, TX (United States). Dept. of Mechanical Engineering
Temperature-dependent effective thermoelastic properties of fiber composite materials and associated microscopic thermal residual stresses are important in designing flight and propulsion structures which may experience large temperature traverses during service. To minimize thermally induced stresses and failure in high temperature environments, accurate predictions of temperature-dependent thermoelastic properties and associated microscopic thermal stresses in the composites are essential. A homogenization theory for high-temperature composites has been developed in the authors` laboratory and is applied here to carbon-fiber-reinforced polyimide composite systems subjected to a large temperature traverse. The theory involves a two-scale asymptotic expansion in microscopic and macroscopic coordinates that relate to the unit cell and the overall structure. Governing differential equations are derived for each order of the expansion. To solve for disturbed displacements in high-order forms, a numerical method with an eigen strain concept, using an incremental scheme along the temperature traverse, is employed. Averaging the high-order solutions through the cell, one obtains temperature-dependent, effective thermoelastic properties of the fiber composite. Simultaneously, microscopic thermally-induced residual stresses and deformations in the composite are also determined. High-temperature experiments to determine the temperature-dependent thermoelastic moduli and thermal expansion coefficients are performed on a carbon-fiber reinforced polyimide composite in order to validate the predictions. The homogenization predictions and the experimental results are found in excellent agreement over the entire range of temperature considered in the study.
- OSTI ID:
- 89782
- Report Number(s):
- CONF-9409291--; ISBN 1-56676-220-0
- Country of Publication:
- United States
- Language:
- English
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