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A reconsideration of a previous study of the transmission loss of sandwich panels is presented. An erroneous calculation of the transmission loss is corrected, and new results are presented. Also, some interesting implications for the design of walls of high transmission loss are pointed out. Subject Classification: [43]55.75.

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The flutter behavior of clamped plates exposed to transverse pressure loadings, or buckled by uniform thermal expansion has been investigated theoretically, and the results compared with existing experimental data. Quasi-steady aerodynamic theory and von Karman's plate equations are employed. Two sets of in-plane boundary conditions are considered: 1) zero in-plane motion normal to the edges, and 2) zero in-plane stress at the edges. A modal expansion of the transverse deflection is used in conjunction with Galerkin's method to obtain a set of nonlinear ordinary differential equations which are integrated numerically to determine the flutter motion. Good correlation is obtained between experimental and theoretical flutter boundaries for plates exposed to a, static pressure differential. The stability boundaries of low aspect ratio plates with zero edge restraint are found to be more sensitive to pressure loads than are those of plates with complete edge restraint. Moreover, comparisons with available experimental data indicate that zero edge restraint is a good assumption for some panel configurations. Finally, it is indicated that fair agreement between theory and experiment can be obtained for buckled plates. Nomenclature a = plate length a n = modal amplitude b = plate width c = speed of sound d = cavity depth D == Eh*/12(l -? 2 ) = plate stiffness E = Young's modulus h -plate thickness I = area moment of inertia K = (^(pmha^/D) 112 = dimensionless radian frequency k X} ky = in-plane spring constants Presented at the AIAA Structural Dynamics and Aeroelasticity M = Mach number N x ,N y = in-plane stresses p = pressure P = pa^/Dh = dimensionless pressure t = time u = plate in-plane displacement, x direction U = flow velocity v = plate in-plane displacement, y direction w = transverse plate deflection x,y,z = plate coordinates a = coefficient of thermal expansion oix,oi y = in-plane restraint parameters [see Eq. (15)] ft = (M 2 -1) 1/2 Ap = static pressure differential AP = Apa*/D = dimensionless static pressure differential AT = temperature differential A*, A y = in-plane stretchings [see Eq. (5)] n = pa/pmh = dimensionless flow density v = Poisson's ratio p = air density p m = plate density r = t(D/p m ha*) 112 = dimensionless time Downloaded by UNIVERSITY OF ARIZONA on February 3, 2015 | http://arc.aiaa.org |

No abstract