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A programmed heat-activated foam technology has recently been introduced for making baffles to seal hollow car body channels[1,2]. First, we summarize the key characteristics of the programmed foams. Some unique design features such as maximum gap to allow easy E-coat drainage, multiple section design for complex channels, allowance for passage of drainage hose and double-layered baffle are presented. Then, we examine the important design parameters affecting the acoustic performance of baffles based on the programmed foams. The insertion loss(IL) was measured for various baffles expanded in a test channel. The effects of foam expansion ratio, surface density, etc., on the acoustic performance of various single-layered and double-layered baffles are reported.

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.