Wednesday, 13 October 2004 - 2:40 PM

This presentation is part of : Micro- and Nano-scale Materials Characterization I

Rheological Modeling of Nanoindentation Contact at Studying Fracture Mechanics of Multi-Layered Coatings

Maksim Kireitseu, Institute of Mechanics, Lesnoe 19-62, Minsk, 223052, Belarus and Igor Nedavniy, Institute of Strength Physics and Materials Science, Siberian Branch of Russian Academy of Sciences, Pr. Academicheskii 2/1, Tomsk, 634021, Russia.

Diamond-containing nanocomposites and carbon nanotubes were grown directly on carbon fibers using chemical vapor deposition. When embedded in an aluminum or polymer matrix, the change in length scale of carbon-based nanoparticles relative to carbon fibers results in a multiscale composite, where individual carbon fibers are surrounded by a sheath of nanocomposite reinforcement. Nanocomposite multilayered materials were fabricated to examine the influence of local carbon nanoparticle reinforcement on load transfer at the fiber/matrix interface. Results of the single-fiber composite tests indicate that the nanocomposite reinforcement improves interfacial load transfer. Selective reinforcement by nanotubes at the fiber/matrix interface likely results in local stiffening of the polymer matrix near the fiber/matrix interface, thus, improving load transfer. The nanocomposites were developed for their applied researches in aerospace industry at NASA NCAM center. The use of indentation at micro and nanoscales with rheological models as a method for determining the fracture of multi-layered brittle coatings is described. While Hertzian indentation advantage of the method revealed here is that, the only quantity to be measured is a deformation or a fracture load. By measuring this minimum load (and that is the only quantity that must be measured) an accurate estimate of fracture may easily be made with application of rheological modeling. Analysis of the models may help in better understanding of nanocoatings failure and degradation mechanics. Multi-layered nanostructured coatings exhibit linear relation of stress curve, whereas while unloading coating may show an effect of retardation of deformations that is also known as an elastic return.

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