VIBRATION DAMPING CHARACTERISTICS OF LAMINATED STEEL SHEET

The use of laminated steel sheets as vibration damping materials was studied. The laminate consisted of a viscoelastic layer which was sandwiched between two steel sheets. The study sought to identify parameters affecting the damping efficiency of the laminate. Two viscoelastic materials, a copolymer based on ethylene and acrylic acid (PEAA) and polyvinyl butyral (PVB), were used. A frequency analyzer was used to measure the loss factor of the laminates. A theoretical analysis of damping efficiency based on a model described by Ungar[2] was also carried out. The results showed that the loss factor of the PEAA-based laminates increased monotonically with increasing thickness of the viscoelastic layer and leveled off at 25.9 pct of total thickness. Ungar's theory predicted a higher loss factor than the experimental data. This might have resulted from interfacial adhesive bonding, a nonuniform viscoelastic layer thickness, and the extrapolation of the rheological data from low to high frequencies. The loss factor of the laminate increased with increasing temperature, reached a maximum value, and then decreased. An optimum temperature for maximum damping was found for each laminate configuration. The PEAA-based laminates possessed higher damping efficiency than the PVB-based laminates at room temperature. The symmetric laminate (with the same steel sheet thickness) possessed a better damping efficiency than asymmetric laminates. The maximum damping peak of the laminates using a polymer blend, when compared to the laminates using unblended resin, exhibited a lower loss factor value, became broader, and occurred at a temperature between the T(g)'s of the individual components of the polymer blend.