Polyurethane Foam Inserts for NVH and Structural Applications

The application of two-component polyurethane (PU) foam materials for acoustical and structural performance enhancements in vehicle structures have increased significantly in the past ten years. The benefits include NVH management (through effective cavity sealing), body stiffness improvements and energy management in crash applications. These PU foams can either be pumped into body cavities in the OEM assembly plants (bulk applied) or can be pre-molded into Structural Foam Inserts (SFI) and installed in the body-shop prior to full frame assembly. The choice of application type depends on vehicle-specific requirements and assembly plant criteria. The chemistry, plant application and benefits associated with bulk PU foam has already been cited in previous work.^{1, 2, 3} This paper showcases BETAFOAM™ SFI technology developed by Dow Automotive that complements traditional bulk foam technology.

The SFI is fabricated by molding rigid polyurethane foam into pre-formed shapes designed to nest into vehicle sheet metal cavities. The material properties of the foam can be tailored to meet specific application performance requirements. A heat activated expandable structural adhesive encases this cast foam. During assembly, the “drop-in” insert is attached to the body structure in the areas needing reinforcement. As the vehicle body passes through the ELPO-bake oven, the adhesive expands and bonds the foam core to the surrounding sheet metal structure. This strong SFI to sheet metal bonding ensures a good sectional integrity - a primary requirement for improving NVH and energy transfer characteristics.

The primary focus of this paper is to discuss this new technology and its potential areas of application for performance enhancement. An attempt will be made to differentiate this technology from the traditional bulk foam technology and discuss its merits.