Enhanced laminate damping via modification of viscoelastic interlayer

This study sought to develop a sandwich‐type vibration damping laminate suitable for room‐temperature applications. The laminate consisted of a polymeric interlayer that was sandwiched between two steel sheets. The study was initiated to promote the relatively low‐damping capability of a maleic anhydride‐grafted polypropylene (mPP)‐based laminate, which failed to meet the requirement that the loss factor of the laminate should be greater than 0.05 for effective damping. Modifications of mPP by incorporation of a dynamically vulcanized PP/butyl rubber blend were then followed. The modifications were based on the theoretical analysis proposed by Rose, Ungar, and Kerwin (RUK) for a general polymer‐based laminate. The design criteria for the polymeric interlayer, i.e., the preferred range of storage modulus G′ for a set of reasonable values of loss tangent (tan δ), were first established from calculations by use of the RUK theory. The theoretical calculations revealed that the low damping of the mPP‐based laminate resulted primarily from the high G′ and low tan δ of the interlayer. Incorporation of butyl rubber into the polymeric interlayer led to a strong decrease in G′ and a moderate increase in tan δ. These modifications resulted in significantly improved damping capability of the laminate, as predicted by the RUK theory.