Carbon nanotubes (CNTs) are rolled up sheets of graphite that form into a
tube with only one layer of carbon atoms (single walled carbon nanotubes) or a
tube with many layers of carbon atoms (multi wall carbon nanotubes) with
diameters in the nanometer range and only a few microns in length.
The carbon-carbon bond in addition to the unique rolled up structure give
carbon nanotubes a rare combination of excellent mechanical, electrical and
thermal transport properties.
Due to their excellent mix of properties, small size and high aspect ratios
(length to diameter ratio) carbon nanotubes can be incorporated into different
materials to form composites with a wide range of functional capabilities.
Polymer-Carbon Nanotube Composite
When incorporated into polymers, for instance, the high conductivity of
carbon nanotubes transforms the polymer composites into electrical conductors at
very low nanotube contents.
If the polymer-carbon nanotube composite is subjected to mechanical load, a
change in the electrical resistance results. This change could arise from the
loss of contact between neighboring CNTs or increase in the inter-tube distances
which results in a rise of tunneling resistance.
High sensitivity of carbon nanotube composites to mechanical strain means
that they can be used as sensors for detection of strain, force and pressure in
engineering structures, such as bridge.
Carbon Nanotube as Strain Sensors for Structural Health Monitoring
These carbon nanotubes strain sensors open a new way of developing cheaper
multifunctional sensing units for structural health monitoring.
Tiny multiple-point sensors could be used to monitor and feed the state of
structural health to a central collection point, making it easier to manage and
maintain large structures.
The expected benefits to society include enhanced safety, reduced maintenance
cost and improved asset lives.
Our current work involves investigating the effects of operating environment
on the mechanical and electrical performance of bulk and thin film carbon
nanotube composites as strain sensors.
A fundamental understanding of the effects of environmental temperature,
moisture and loading modes on electrical behavior of these sensors is critical
for any practical application.
Designs that allow reliable performance, multi-directional sensing and
flexible installation are of particular interest for wide acceptance of carbon
nanotube strain sensors over conventional ones.
Copyright AZoNano.com, Professor Cheng Yan (Queensland
University of Technology)
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