Acoustic Radiation From an Infinite Laminated Composite Cylindrical Shell With Doubly Periodic Rings

Abstract

Acoustic radiation from a point-driven, infinite fluid-loaded, laminated composite shell, which is reinforced by doubly periodic rings, is investigated theoretically. The theory is based on the classical laminated composite shell theory, the Helmholtz equation, and the boundary conditions at the shell-fluid interface as well as at the junctions between the shell and the rings. The rings interact with the shell only through normal forces. The solution for the radial displacement in wave number domain is developed by using Mace’s method (1980, “ Sound Radiation Form a Plate Reinforced by Two Sets of Parallel Stiffeners,” J. Sound Vib., 71(3), pp. 435–441) for an infinite flat plate. The stationary phase approximate is then employed to find the expression for the far-field pressure. Numerical results are presented for discussion of the effects of lamination schemes, Poisson’s ratios, ply angles, and damping on the far-field acoustic radiation, which may lend themselves to better understanding the characteristics of acoustic radiation from the laminated composite shells. In addition, the helical wave spectra of the stiffened cylinders are presented, in which the effects of wave number conversion due to the periodic rings are obviously identified as additional bright patterns.