摘要

An analytic model is developed to investigate the wave propagation and sound transmission characteristics of an infinite sandwich structure reinforced by two sets of orthogonal rib-stiffeners when subjected to convective fluid-loaded pressure. The rib-stiffeners are assumed to be identical and uniformly spaced, which can exert not only tensional forces and bending moments but also torsional moments on the facesheets. Inertial terms of the tensional forces, bending moments and torsional moments are introduced to account for inertial effects arising from the mass of the rib-stiffeners. With the surrounding acoustic fluids restricted by the acoustic wave equation, fluid-structure coupling is considered by imposing velocity continuity condition at fluid-panel interfaces. By applying the Bloch theorem for periodic structures, the structural and acoustic responses are expressed in a superposition form of space harmonics for a given wavenumber. The application of the virtual work principle for one periodic element yields two infinite sets of simultaneous algebraic coupled equations, which are numerically solved by truncating them in a finite range insofar as the solution converges. The validity and feasibility of the analytic model is qualified by comparing model predictions with existing results, in which the necessity and advantage of the exact modeling of rib-stiffener motions are also demonstrated. Specifically, the influences of inertial effects arising from rib-stiffener mass, the periodicity spacing of rib-stiffeners, and the airborne as well as structure-borne paths on the transmission of sound across the sandwich structure are quantified and conclusions of significant practical implications are drawn.