Nonlinear Analysis of the smart composite sandwich plates and shells has been presented. Active fiber composite (AFC) material is used as the material of constraining layer of the active constrained layer damping (ACLD) treatment for controlling geometrically nonlinear transient vibrations of sandwich plates and shells. The Golla-Hughes-McTavish (GHM) method is implemented to model the constrained viscoelastic layer of the ACLD treatment in time domain. Emphasis has been placed on investigating the effects of the variation of piezoelectric fiber orientation angle in the AFC constraining layer on the damping characteristics of the overall sandwich structures.