375
porous materials in many diverse applications, from thermal insulation to filtration devices, is huge, and consequently considerable
work has been done in this general area, albeit comparatively little
with respect to sound-damping applications. Damping vibrations
require energy dissipation associated with mechanical movements
and hence require special properties not found in many nanoporous materials developed for other applications such as nanoporous gels for thermal applications. Still, additional developments
can be expected here, especially for use in small damping devices.
Other composites based on nanomaterials have been found to have
damping properties. Many polymers are already well known for
their viscoelastic qualities and have found use in damping devices.
There has also already been an enormous amount of research in
polymer nanocomposites, particularly with respect to strength
properties and to electrical properties. The use of polymer nanocomposites for damping is possible. Polymer nanocomposites using
carbon nanotubes, in particular, have been explored. In strength
and stiffness studies, carbon nanotubes have been found to have
attractive strength properties. There can, however, be considerable
sliding at nanotube-to-nanotube interfaces that can seemingly
be a problem for some applications, but, on the other hand, this
same interfacial sliding can have beneficial damping characteristics.
The interfacial sliding appears to create frictional energy dissipation that leads to improved damping characteristics. Considerably
more research work needs to be done in this area before significant
applications can develop. Many difficult issues, such as achieving
uniform dispersions and temperature effects, are comparable to
those in other polymer nanocomposite research. Other types of
nanofillers have also been suggested for use in damping. Though
applications remain largely in the future, it does appear that for
many small-scale applications such as small speakers, this approach
could prove valuable.
Many existing interesting damping-control devices are based on
active control systems, and nanomaterials could possibly enhance
their performance. The use of magnetorheological devices for
damping has been widely explored, even for large applications in
buildings and bridges. The viscoelastic properties of magnetorheological materials can be altered with changes in surrounding magnetic fields, which in turn can be electronically controlled. Devices
have been developed that have sensors detect vibratory movements.
Magnetic fields and resultant material stiffnesses are then appropriately controlled. The unique magnetic properties of nanomaterials make their use particularly attractive in conjunction with
Sound and Acoustical Environments
porous materials in many diverse applications, from thermal insulation to filtration devices, is huge, and consequently considerable
work has been done in this general area, albeit comparatively little
with respect to sound-damping applications. Damping vibrations
require energy dissipation associated with mechanical movements
and hence require special properties not found in many nanoporous materials developed for other applications such as nanoporous gels for thermal applications. Still, additional developments
can be expected here, especially for use in small damping devices.
Other composites based on nanomaterials have been found to have
damping properties. Many polymers are already well known for
their viscoelastic qualities and have found use in damping devices.
There has also already been an enormous amount of research in
polymer nanocomposites, particularly with respect to strength
properties and to electrical properties. The use of polymer nanocomposites for damping is possible. Polymer nanocomposites using
carbon nanotubes, in particular, have been explored. In strength
and stiffness studies, carbon nanotubes have been found to have
attractive strength properties. There can, however, be considerable
sliding at nanotube-to-nanotube interfaces that can seemingly
be a problem for some applications, but, on the other hand, this
same interfacial sliding can have beneficial damping characteristics.
The interfacial sliding appears to create frictional energy dissipation that leads to improved damping characteristics. Considerably
more research work needs to be done in this area before significant
applications can develop. Many difficult issues, such as achieving
uniform dispersions and temperature effects, are comparable to
those in other polymer nanocomposite research. Other types of
nanofillers have also been suggested for use in damping. Though
applications remain largely in the future, it does appear that for
many small-scale applications such as small speakers, this approach
could prove valuable.
Many existing interesting damping-control devices are based on
active control systems, and nanomaterials could possibly enhance
their performance. The use of magnetorheological devices for
damping has been widely explored, even for large applications in
buildings and bridges. The viscoelastic properties of magnetorheological materials can be altered with changes in surrounding magnetic fields, which in turn can be electronically controlled. Devices
have been developed that have sensors detect vibratory movements.
Magnetic fields and resultant material stiffnesses are then appropriately controlled. The unique magnetic properties of nanomaterials make their use particularly attractive in conjunction with
Sound and Acoustical Environments