| Speaker : |
Prof. William Curtin (Division of Engineering, Brown University) |
| Subject : |
Mechanical Properties of Carbon-Nanotube Ceramic Matrix Composites |
| Date : |
June 15, 2004 (Seminar room 2, Basic Experimental bldg., Kashiwa campus) |
| Abstract : |
The excellent mechanical properties of carbon-nanotubes are driving research into the
creation of new strong, tough nanocomposite systems. Here, the evidence of toughening
mechanisms operating in carbon-nanotube-reinforced ceramic composites is presented. A
highly-ordered array of parallel multiwall carbon-nanotubes (CNTs) in an alumina matrix was
fabricated. Nanoindentation introduced controlled cracks and the damage was examined by
SEM. These nanocomposites exhibit the three hallmarks of toughening in micron-scale fiber
composites: crack deflection at the CNT/matrix interface; crack bridging by CNTs; and CNT
pullout on the fracture surfaces. Interface debonding and sliding can thus occur in materials
with microstructures approaching the atomic scale. Furthermore, for certain geometries a new
mechanism of nanotube collapse in "shear bands" occurs, rather than crack formation,
suggesting that these materials can have multiaxial damage tolerance. Evidence for a novel
nanotube fracture mode is also presented. |
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