Evaluation of Liquid Applied Dampers: Impact of Polymer-Inorganic Interface on Performance 2017-01-1877
Damping materials are applied to the vehicle body during production to provide passenger comfort by reducing noise and structural vibration through energy dissipation. Noise, Vibration, and Harshness (NVH) Engineers identify critical areas of the vehicle body for material placement. Damping materials, which include liquid applied dampers, are typically applied directly on the structure, covering large areas. These film forming materials can be spray applied using automation and, after baking, result in a cured viscoelastic damping layer on the target substrate. Typical liquid applied dampers contain an aqueous dispersion of film forming polymer which functions to bind inorganic materials together in the coating and provide a composite structure that dissipates energy. Representative damping coatings were prepared from dispersions of polymers with varying viscoelastic properties and chemical compositions. These coatings were analyzed to determine performance properties and internal coating structure. Vibrational damping of the materials was measured using Oberst bar testing. Dynamic Mechanical Analysis (DMA) was used to measure the intrinsic properties of the polymers and coatings, including the storage moduli, loss moduli, and tan delta. Scanning Electron Microscopy of the colloidal dispersions, liquid dampers, and final baked coatings was used to study structure-property relationships at sub-micron scales. The results indicate that composition of the polymer dispersion strongly impacts the interaction of the polymer with the inorganic materials, the structure of the final coating, and the overall performance of the liquid applied damper.