Acoustic scattering from finite bilaminar composite cylindrical shells with doubly periodic stiffeners—3-D solution

The acoustic scattering from an insonified finite bilaminar cylindrical shell is analyzed. The shell is reinforced by a two sets of rib-stiffeners to form a doubly periodic stiffened shell. The two cylindrical shell laminates are perfectly bonded having the same lateral dimension but have different radii and material properties The two sets of rib-stiffeners have rectangular cross-sections and are perfectly bonded to the inside of the inner shell. One set of stiffeners is heavy and the other set is light, so that a finite number of light stiffeners are set within every pair of heavy stiffeners. The bilaminar stiffened shell is analyzed using the exact theory of three-dimensional elasticity. The stiffeners are analyzed as elastic rings with extensional, torsional, and in-plane and out-of-plane flexural rigidities. The scattered acoustic farfield is evaluated for various incident plane wave frequencies. Shells with different combinations of light to heavy stiffener geometries are analyzed. A uniform steel stiffened shell submerged in water and stiffened with doubly periodic stiffeners was initially analyzed. A second shell made up of an outer elastomer shell bonded to an inner stiffened steel shell was also analyzed. [Work supported by NAVSEA Division Newport under ONR Summer Faculty Program.]