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Baffles based on heat activated foams have found increasing use as body cavity filler to inhibit noise propagation through hollow body channels, such as pillars in passenger cars. However, most conventional expandable foams tend to sag, deform and foam randomly, unless they are supported or sandwiched by rigid plastic or metal plates. The uncontrolled foaming reduces the reliability of cavity sealing for fumes, water and noise. The sandwich designs add to the part weight and increase cost unnecessarily. This paper introduces a heat activated expandable foam with programmed directional control during expansion. The directional control is especially useful for filling cavities such as pillars with complex geometry or sharp pinch-welded corners; it also eliminates the need for sandwich design. To demonstrate the effectiveness of the foams with directional control, the dynamics of cavity filling was studied by comparing programmed foaming with random foaming.

Constrained layer damping (CLD) is a well known technique to efficiently damp low frequency vibration. CLD employs a viscoelastic material sandwiched between two very stiff, typically metal, layers. While effective over essentially flat surfaces, CLD has not been applicable to cylindrical shapes. In order to damp low frequency vibration in metal pipes, users have been forced to rely on extensional layer damping, typically consisting of thick layers of extruded or molded rubbers. This paper discusses a novel product to damp cylindrical articles such as metal pipes with a constrained layer heat shrink tubing. This product utilizes a stiff heat shrinkable polymeric jacket bonded on the inside with a viscoelastic layer. When shrunk on a metal pipe or rod, a CLD system is produced. The product is typically thinner than an extensional layer damper and is more effective. It also meets the other physical and environmental requirements for a pipe covering.