What are the differences between smart materials, composite materials and nano materials?

Smart materials are at least dual function, composites are materials composed of dissimilar phases or components (sometimes they’re called hybrid materials now), and Nano materials have been engineered on the Nano-scale

Smart materials have multiple functions, which generally include sensor/actuator ability in addition to having form, or being able to support at least some structural weight. The classic example is Nitinol, which is a Nikcle-Titanium allow. After mechanical deformation (for example, bending), it can be heated up and will return to the pre-deformed structural shape. Lead-Zirconate-Titanate (PZT) is a ceramic, which responds to mechanical deformation by generating an electrical potential. In the reverse, an applied electrical potential leads to a geometric expansion of the material (actuator function).

Composites are materials that are combinations of at least two different materials, which allow the engineering of desired properties (like tailoring mechanical stiffness, conductivity, etc). Classic examples are glass fiber composites, where glass fibers are embedded in an epoxy matrix. As long as the base materials retain their characteristics and physical morphology, it would be considered a composite.

Nano-materials implies that the material has been designed and engineered at the Nano-scale. This might include creating nano-sized fibers or particles for the creation of composites, building surfaces, etc.