|Smart Materials 101
|Mon, 19 Jan 1998 22:56:37 EST
Okay, since a lot of people have asked about smart materials, it's time for me
to shed a little light on the subject.
The idea for smart materials came from an article that I read in the Army
Times (a weekly newspaper that sells on US Army posts and covers issues
relevant to Army service members). The article was published several years
ago, and unfortunately I don't have the article on me anymore. But more on
First let's start with the basics---piezoelectricity:
Piezoelectricity is a special property that exists in certain materials,
particularly certain types of quartz crystals. If you squeeze them, equal but
opposite charges appear on opposing surfaces of the wafer. Conversely, if you
apply a voltage across the opposing faces of the wafer, the dimensions of the
wafer change. Piezoelectricity is used in a number of applications that
translate mechanical oscillation into electric signals (e.e., the voice
receiver of your telephone) or vice versa (sonar transmitters).
Now, in the case of smart materials, different piezoelectrics are layered one
atop another in a certain way. When a voltage is applied across the structure,
one set of piezoelectric expands in one direction, while another contracts in
the opposite direction. This creates a shearing force that "warps" the
material and causes it to twist and bend.
Now, back to the article I read, designers in the DoD are researching using
these layered piezoelectrics in helicopter rotors. In the rotor of a
helicopter, the aircraft changes the pitch of the blades to generate motive
force; in the main rotor, changing the pitch causes the helicopter to go up
and down, while in the tail rotor changing the pitch causes it to turn left or
To get the pitch of the rotor blades to change, currently designers use
mechanical actuators of rods and gears. It's these actuators that mainly
contribute to the helicopter's chopping sound, by generating a turbulent
"eggbeater effect." Additionally, these actuators also cause drag that slows
down the helicopter and reduces maneuverability. Also, all these moving parts
drives up the maintenance cost, and they add extra weight.
What the designers hope to achieve is to design a single main rotor with smart
materials. That way, in order to change the blade pitch, all they have to do
is apply a voltage across the rotor. This eleiminates the mechanical
actuators, and thus eliminates noise, increases maneuverability, reduces
weight, and lowers maintenance costs (in terms of $$$, inventory, down time,
Of course, all of this is still in the experimental stage right now, so
there's no guarantee smart materials (in RL) may live up to all the benefits
that have been claimed about it. But assuming it does (which I did), the
obvious benefits to other vehicles are quite self-evident (as reflected in
Rigger 2 on p. 117).
Now, what can and can't smart materials do? (IMO)
* Smart materials allows a relatively study component (like a rotor) to twist
(around an axis) and bend into an arc, much like a rubber eraser.
Theoretically, one could get 360+ degree twists, but practically, even with
2060-era engineering, the practical (production) limit would be 90 degrees,
with 180 as the technological limit.
* Smart materials can't change the overall shape and form of an object (like
Spawn's symbiote-suit, or the T-1000 liquid metal Terminator). Smart materials
allow a solid object limited deformation under an electric field, but once the
electricity is turned off, it snaps back to its original shape. Smart
materials are not malleable and should NOT be thought of as self-forming clay.
* Manufacturing smart-material components requires some precise layering and
placement of piezoelectric composites. As such, they probably would not stand
up well to physical shock. So smart materials would probably make for a very
poor (and very fragile) melee weapon.
That's about all I can guess about smart materials. If anyone else has any
other creative uses for smart materials, I'd love to hear it.
Hope this helps,