ENHANCED LAMINATE DAMPING VIA MODIFICATION OF VISCOELASTIC INTERLAYER

This study sought to develop a sandwich-type vibration damping laminat e suitable for room-temperature applications. The laminate consisted o f a polymeric interlayer that was sandwiched between two steel sheets. The study was initiated to promote the relatively low-damping capabil ity of a maleic anhydride-grafted polypropylene (mPP)-based laminate, which failed to meet the requirement that the loss factor of the lamin ate should be greater than 0.05 for effective damping. Modifications o f mPP by incorporation of a dynamically vulcanized PP/butyl rubber ble nd were then followed. The modifications were based on the theoretical analysis proposed by Rose, Ungar, and Kerwin (RUK) for a general poly mer-based laminate. The design criteria for the polymeric interlayer, i.e., the preferred range of storage modulus G' for a set of reasonabl e values of loss tangent (tan delta), were first established from calc ulations by use of the RUK theory. The theoretical calculations reveal ed that the low damping of the mPP-based laminate resulted primarily f rom the high G and low tan delta of the interlayer. Incorporation of b utyl rubber into the polymeric interlayer led to a strong decrease in G' and a moderate increase in tan delta. These modifications resulted in significantly improved damping capability of the laminate, as predi cted by the RUK theory.