Random vibration analysis of stiffened honeycomb panels with bevelededges

Abstract

A semi-empirical theory is presented for predicting the dynamic strains in the face sheets of honeycomb panels subjected to random acoustic loading. The honeycomb panels are constructed with beveled edges that terminate in a solid panel edge strip around the panel periphery for ease of attachment to the substructure with countersunk fasteners. It is shown that the rotation of the beveled edges introduces a linear dynamic membrane strain into the inner face sheet superimposed on the bending strain. Furthermore, the extensional stiffness of the beveled edge closeout pan is shown to provide the dominant contribution to the honeycomb core shear stiffness exceeding that of the core alone by almost an order of magnitude. Good agreement is obtained between the predicted and measured strains, the latter taken from existing test data representing a wide range of honeycomb panel dimensions. Nomenclature =panel overall length and width, respectively =equivalent panel length and width, respectively =inner and outer face sheet strain parameters defined by Eqs. (44) and (45), respectively =equivalent honeycomb beam length and inner face sheet length, respectively =speed of sound in air =Young's modulus of both face sheets and of the closeout pan, respectively =natural frequency of the m,nth mode =actual and equivalent shear modulus, respectively, of the honeycomb core =constant power spectral density of the random acoustic excitation =honeycomb core height =direct joint acceptance for the m,nth mode = shear-related parameter, Eq. (33) =small part of the solid panel edge width (Fig. 6) =length of the closeout pan =mass per unit area of honeycomb panel, Eq. (3) =bending moment at beveled edge =mode number parallel to the x and y axes, respectively =shear stress and equivalent shear stress, respectively =subscript denoting the m,nth mode =solid panel edge width = unreacted forces per unit length at beveled edge of honeycomb beam (Fig. 7) =in-plane forces per unit length in the inner and outer face sheets, respectively, at the beveled edge of honeycomb beam =in-plane forces per unit length in the solid panel edge and pan, respectively, of honeycomb beam =variable in-plane force in the inner face sheet of honeycomb beam parallel to they axis =thickness of each face sheet, each adhesive layer, and the pan, respectively