THE EFFECT OF VISCOELASTIC ADHESIVE LAYERS ON STRUCTURAL DAMPING OF SANDWICH BEAMS

The effects of a viscoelastic adhesive layer on the dynamic response a nd structural damping of sandwich structures are studied by employing a newly developed sandwich beam theory. The two face layers are consid ered as ordinary beams (Euler beams) with both axial and bending resis tance. The core material is considered to be viscoelastic. A newly dev eloped high-order displacement field assumption is used in order to ac hieve a more accurate kinematics of the flexible viscoelastic core tha n would be possible under the classical assumptions for sandwich beams . Imperfect interface conditions between faces and core are defined as linear relations between longitudinal displacement discontinuities an d the transverse shear stress at the adhesive layer. The viscoelastic properties of the adhesive layer and the core material are assumed in a complex modulus formula that is a function of frequency for a given temperature. The linear equations of motion that describe the vibratio n of the sandwich finite beam are derived based on the Hamilton princi ple. Consistent boundary conditions are given by prescribing either th e stress resultants or the corresponding time derivatives of the displ acement components. The numerical results of a mechanical impedance ex ample are verified with experimental data in the literature. The effec ts of storage modulus and loss factors of adhesive layers are investig ated numerically for simply supported beams under harmonic excitation. It is shown that the viscoelastic adhesive layers have a definite inf luence on structural damping of the sandwich beam.