A semi-analytic method is developed to predict vibro-acoustic responses of functionally graded cylindrical shells with arbitrary boundary conditions. Material properties vary continuously in thickness direction according to four-parameter power-low distributions in terms of volume fractions of two constituents. The shell is firstly divided into many narrow strips in axial direction. By employing first-order shear deformation theory (FSDT) and expanding displacements as the exponential functions and Fourier series in axial and circumferential directions, five displacements and five forces at any cross-sections are expressed as 10 unknown coefficients. Surface Helmholtz integral equation which is adopted for external acoustic pressure is reduced to line integral through expanding pressure and velocity as Fourier series in circumferential direction, and the pressure can be further represented by displacement functions of all strips after meshing the line integral to some 3-node isoparameter elements and utilizing the relationship between displacement and velocity. Boundary conditions and continuity conditions which contain effects of acoustic pressure are orderly assembled to the final governing equation. By comparing vibro-acoustic results of present method with the ones calculated by FEM/BEM, rapid convergence and high accuracy are demonstrated. Furthermore, effects of material parameters and external fluid are studied.
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