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Stability and structural integrity are extremely important in the design of a vehicle. Structural foams, when used to fill body cavities and joints, can greatly improve the stiffness of the vehicle, and provide additional acoustical and structural benefits. This study involves modal testing and finite element analysis on a sports utility vehicle to understand the effect of structural foam on modal behavior. The modal analysis studies are performed on this vehicle to investigate the dynamic characteristics, joint stiffness and overall body behavior. A design of experiments (DOE) study was performed to understand how the foam's density and placement in the body influences vehicle stiffness. Prior to the design of experiments, a design sensitivity analysis (DSA) was done to identify the sensitive joints in the body structure and to minimize the number of design variables in the DOE study.

This paper describes a comprehensive hybrid technique developed for optimization of damping materials on vehicle bodies. This technique uses finite element analysis (FEA) along with experimental techniques to complement each other. In this particular application, a hybrid technique was used to address floorpan vibration and the resulting radiated noise. The objective of this approach was to develop an optimized damping material application layout. This optimized layout balances the increased performance with the overall material volume, mass, and cost. The optimized damping material application developed resulted in a 3-5 dB reduction in the floorpan vibration level while saving 10% in material volume and mass. This optimized layout was validated on a body-in-white using a laser vibrometer. In addition, a new liquid applied material was also introduced with better damping characteristics.