Materials for Noise and Vibration Control: What Causes Product Variability?

The Society of Automotive Engineers has selected a paper written by this associate for inclusion in SAE's 2006 Transactions. Described as among the best SAE Technical Papers published 2006, it will be published in one of seven subject-specific volumes.

Abstract

Many methods for damping - attenuating - unwanted noises and vibrations found in vehicles, engineering components, and electronic systems are available. A special type of damping material involves polymer-based coatings whose compositions may be "tuned" to attenuate vibration that may occur over specific temperature ranges. These coatings exhibit both elastic flow and viscous flow, depending on their temperature, and are commonly referred to as viscoelastic materials. Today, viscoelastic materials are used to fabricate many types of engineering components for automotive applications, including engine oil pans, valve covers, dash panels, and shims or insulators for brake noise damping.

No matter their application, expected performance for viscoelastic damping materials is based on two factors : (1) the quality and durability of coating-to-substrate interfaces; (2) the quality and durability of the viscoelastic coating itself. Thus, performance is a complex function of the individual materials and processes used in fabricating the damping material, including but not limited to substrate cleaning and pre-treatment, choices of primers, solvent removal, coating composition, and proper curing.

The paper provides an analysis of potential failure modes of interfaces and coatings in viscoelastic damping materials and reviews their effects on performance. Background information includes comments and data on proper selection of materials, processing parameters, and how damping characteristics may be compared. The oral presentation emphasized materials and their application to damping vehicle brake noise. This approach provides a tutorial on the many factors that should be considered in managing and reducing variability in quality and performance.

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