Stress rupture of unidirectional polymer matrix composites in bending at elevated temperatures
<p>A new method for stress-rupture experiments in bending has been developed and used to characterize unidirectional polymer matrix composites. The method. which makes use of very simple fixtures, led to coherent results. These results have been modeled using the large deflection of buckled ba...
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| Format: | Others |
| Language: | en |
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Virginia Tech
2014
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| Online Access: | http://hdl.handle.net/10919/45398 http://scholar.lib.vt.edu/theses/available/etd-11012008-063348/ |
| Summary: | <p>A new method for stress-rupture experiments in bending has been developed and
used to characterize unidirectional polymer matrix composites. The method. which
makes use of very simple fixtures, led to coherent results. These results have been
modeled using the large deflection of buckled bars theory (elastica) and it is possible to
predict with good accuracy the strain at each point of the specimen if the end-to-end
distance is known. The failure process has been experimentally characterized. The
formation and propagation of microbuckles leads to a compressive failure. Based on the
elastica and the classical lamination theory, a model for the distribution of the Young's
modulus along the length of the specimen has been established. Three different
micromechanical models have been applied to analyze the time-to-failure versus strain
behavior at two temperatures - one below and one above the glass transition. The first
micromechanical model considers the nucleation of the microbuckles as the main cause
of failure. In addition, the stiffness and stress distributions at any time before failure are
calculated based upon the rotation of the fibers in the damaged region. The second and last models, respectively based upon a Paris Law and energy considerations relate the
time-to-failure to the propagation of the main microbuckle. For this last model, a good
correlation between experimental and theoretical data has been obtained. Finally the
influence of the temperature on these models has been studied.</p> === Master of Science |
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