As a first endeavor, the free flexural vibration behavior of doubly curved complete and incomplete sandwich
shells with functionally graded (FG) porous core, FG carbon nanotube reinforced composite (FG-CNTRC) face
sheets and integrated piezoelectric layers is investigated. The variable radii shells with the three most common
types of geometries, i.e., elliptical, cycloid and parabolic, are considered. The system equations are derived based
on the general higher-order shear deformation theory and Maxwell's equation. The generalized differential
quadrature (GDQ) method is employed to discretize the governing partial differential equations subjected to
different boundary conditions. The accuracy and reliability of the approach are verified by comparing the results
with the existing solutions in open literature. The effects of porosity parameter and porosity distribution through
the thickness direction, carbon nanotube (CNT) volume fraction, different boundary conditions and various shell
geometrical parameters on the flexural vibrational behavior of the smart sandwich shell structures are investigated
and useful results are presented.