Those research activities consist of an innovating experimental work on
the so called "Smart Materials". These materials act in particular ways
and times when some specific kind of thermo-mechanical conditions are
applied. When removing those conditions the entire system will recover
its original status.
Particular active materials are shape memory alloys (SMA) made by
Aluminium Copper and Nickel, or by Nickel and Titanium, whose commercial
name is Nitinol. SMA are commonly used as stand-alone structures or as
reinforcing materials in composite structures so to make Smart Materials.
The most common use of SMA has been found in polymers matrix applications
where they work as actuator of the entire composite structure or as
sensors.
The main purpose of these activities was to design and build a particular
actuation system, that consists in a glass fibers (width: 3mm) in epoxy
matrix tube, with embedded four Nitinol wires (length: 200 mm, internal
diameter: 20 mm, maximum thickness: 2 mm). The tube was realized by using
the filament winding technology, with a winding angle of 60°. Those wires
were put along the longitudinal axis of the tube. By heating the SMA
wires over a characteristic temperature, its internal structure changes
showing a macroscopic contraction of the same wires. This process means
an application of a compression stress on the tube so to let it torque
thanks to its anisotropic structure. The particular geometry was the
result of a mathematical modelling. During the testing of that system,
while the Nitinol wires were heated by electricity, the tube showed a
torsion of 4.5°± 0.1°. When removing the electrical power, the entire
system recovers its original status.
This kind of actuator has been supposed as a substitute of the
mechanical and hydraulic systems which are built on airplanes to move the
mobile surfaces on the wings.
The entire work has been brought up by the collaboration of I.M.C.B.
(Composite and Biomedical Materials Institute) C.N.R with C.I.R.A.
(Italian Center of Aerospace Research and D.I.M.P. (Materials and
Production Engineering Department) of the University "Federico II" in
Naples.
During the study of that project many suggestions were proposed
to improve the device design and to increase its functionality. Actually
particular thermo-mechanical processes and better temperature control
systems for the SMA wires are being experimented at the I.M.C.B. to get
more information about the behavior of the shape memory alloys.
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