Acoustic scattering by finite composite plates

Resumo

© 2015, American Institute of Aeronautics and Astronautics Inc, AIAA. All Rights Reserved.Trailing edge scattering is a significant source of sound in aeroacoustics, and elasticity is known to decrease the radiated sound by a process involving coupled acoustic and bending waves. Most of the analysis in the literature is appropriate for metallic plates, which are isotropic. We extend a numerical method, based on the solution of a boundary element method (BEM) with boundary conditions given by the structural problem, to account for anisotropic, composite plates. We perform a comparison between composite and metallic plates with the same thickness and similar bending stiffness. For both cases, elasticity is seen to reduce the scattered sound; composite plates lead to greater reductions of far-field sound due to their lower specific mass and consequent higher fluid loading factor. Results also show that orientation of laminae can be used so as to optimise plates for acoustic radiation at specific Helmholtz numbers k0 of interest: different lay-ups present changes in structural resonance frequencies, and higher acoustic benefits can be obtained by ensuring that a given k0 is between two resonances, in a situation where acoustic excitation and elastic response are in phase opposition.