Molecular dynamics study of tensile strength increase of carbon nanotube reinforced amorphous carbon

Keywords:
carbon nanotube, amorphous carbon, tensile strength, reinforcement

Abstract:
Single-wall carbon nanotubes (CNTs) are the toughest fibres known, and structural materials that incorporate CNTs could have superior properties. Ceramic materials are very hard and resistant to heat and chemical attack, making them useful for applications, say, in coating turbine blades. Unfortunately, however, ceramic materials are very brittle. The excellent mechanical properties of CNTs should be helpful in solving the inherent brittleness of ceramics, which has troubled researchers for a long time. There has been growing interest in using high-aspect-ratio CNTs to toughen ceramic composites. This originates from the notion that CNTs are exceptionally stiff, strong, tough, and that by combining CNTs with brittle ceramics one can impart some of the attractive mechanical properties of the CNTs to the resulting composites.
Though some experiments on CNT reinforced ceramics have been done, with the resulting composite nearly triple its resistance to fracturing, the reinforcement theory is still not clear so far. During the mixture and high temperature ceramic produce process, some of the CNTs must be destroyed and alignment of CNTs can not be exactly strait. Consequently, the theoretical prediction on the strength increase is much more than that from the experimental result.
Since the development of porous carbon material (commonly known as carbon foam) in the late 1960’s, carbon foam has attracted people’s attention because it provides opportunities for material property tailoring for thermal management. The ligament microstructure of carbon foam with suitable processing is controlled to adjust mechanical properties as well as thermal conductivity. To solve the brittleness of the amorphous carbon ligament and to enhance tensile strength, experimental research appears recently where the CNTs were dispersed into the carbonized pitch to achieve carbon foam with CNT reinforced ligaments. Until now, however, how the CNTs increase the tensile strength still remains unclear.
In this paper, by using the molecular dynamics simulation, we study how the interface between CNTs and amorphous carbon interact to each other and thus explain how CNTs can be utilized as “fibers” to increase the tensile strength of amorphous carbon composites reinforced with CNTs. Our molecular dynamic results will be also compared with those from the well-known mixture theory currently used in composite community.

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Nanotech 2006 Conference Program Abstract