The advantages and disadvantage of a SMA can be briefly summarized as the following:
High power density; produces a lot of energy for its size.
High force output; contractile stresses of up to 200 MPa have been demonstrated.
Moderate force output, about 1 N per SCP string.
Increasing the force output can be done by actuating multiple SCP units in parallel.
Thermally-actuated, so actuation speed and force depend heavily on the surrounding environment.
Modeling with linear equations is difficult, as continual heat loss occurs while the actuator is working.
Low strain, around 5% or lower.
Not very fast; cannot handle high-frequency applications above 2-3 Hz.
Very low power efficiency, of about 1% or lower.
Requires electrical current fed from both ends of the actuator. This can be difficult to implement in certain designs.
Unfortunately, presently available Ni-Ti alloys having transformation temperatures above 80℃ are not sufficiently stable for multiple cycle applications. However, for single cycle applications (e.g over-temperature protectors) binary and ternary Ni-Ti alloys with transformation temperatures up to 150℃ are available.