Smart Composite structures have the capability to actively respond to the changing environment while offering significant weight savings and additional passive controllability through ply tailoring. Piezoelectric sensing and actuation of composite laminates is the most promising concept and recently, piezoelectric composites have emerged as a new class of smart materials. These find wide applications as distributed actuators and sensors of smart structures. This book presents the analysis of the active constrained layer damping of the nonlinear vibrations of smart composite structures. Three dimensional finite element models have been developed for the smart laminated composite beams, plates and shells undergoing nonlinear vibrations. A novel type of functionally graded laminated composite shell is also proposed where the material properties of a layer vary across the thickness of the layer. Numerical results are obtained to investigate the performance of the piezoelectric composites for controlling the nonlinear vibrations of smart structures.