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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.

Automotive engineering is taking a deeper look at the role of NVH engineering and design. Controlling the vehicle sound is one of the musts in designing successful automobiles today. While the focus is usually on powertrain noise, this report covers the concept of a new technology of dashmats. This new generation of dashmat is constructed of an absorptive layer, a barrier, and another absorptive layer (ABA). Typically, dashmats are placed inside the vehicle on the firewall between the powertrain and the driver. This dashmat blocks and absorbs powertrain noise as well as the vehicle background noise heard at the driver's ear. This report focuses on two types of competing dashmats-the light weight absorptive dashmat which acts by absorbing the sound rather than blocking it and the new generation of vehicle dashmat (ABA) which performs by blocking and absorbing the powertrain noise as well as the vehicle background noise.

Extensional damping materials are commonly used in the automotive industry to control structure-borne noise. Using the dynamic properties of the material or composite panel, these materials can be represented in vehicle finite element or statistical energy analysis (SEA) models. However, in order to make the detailed design changes to the damping material treatment, proper characterization of the material properties is required. This paper discusses the method of measuring and validating the complex modulus of an extensional damping material using the Oberst beam technique [1]. Also, it is shown that the Ross, Kerwin, Ungar (RKU) analytical model can be utilized to predict damping of composite panels for SEA models [2]. SEA modeling of various composite panel constructions will be examined with supporting measurements.

Vehicle NVH and crash performance are important attributes related to end use customer comfort and safety. Polyurethane foam systems are currently being used to enhance these performance properties for today's automobiles. Most structural urethane foams used for NVH (stiffness & sealing) and energy management applications utilize low viscosity polyols and polymeric diphenylmethane diisocyanates (PMDI) as starting components. These systems can be difficult for the assembly plants to process due to foam leaking out of the vehicle cavities before it is fully cured. In addition, capital intensive ventilation systems are typically required to safely manage a production line utilizing classical PMDI-based foams. This paper will describe how a new syntactic polyurethane foam, with a paste-like consistency, can enhance vehicle NVH and crashworthiness, while improving processing and safety-related issues.

Automotive body structures are developed to meet vehicle performance requirements primarily based on ride and handling, crashworthiness, and noise level targets. The body is made of a multitude of sheet metal stampings welded together. Other closures such as fenders, hood, doors and trunk lid are developed to match body interfaces, to contribute and participate in the overall vehicle response, and to meet the sub-system and system structural requirements. In order to improve performance and achieve weight reduction of the overall vehicle steel structure, new polymeric materials and treatment strategies are available to body structural engineers to optimize the response of the vehicle and to tune vehicle performance to meet specified functional requirements. If early integrated to the design cycle, these materials help not only improve the structural body response, but also decrease the weight of the integrated body structure.

This paper investigates the sensitivities of glass bonding adhesives to the dynamic characteristics of automotive body structures. Experimental modal analysis was conducted to study the damping, response amplitude, and stiffness of different adhesives to a door assembly and a vehicle body. Three different glass bonding adhesives were used in this study. Performance advantages of using these adhesives are given.

Sound absorption is one way to control noise in automotive passenger compartments. Fibrous or porous materials absorb sound in a cavity by dissipating energy associated with a propagating sound wave. The objective of this study was to evaluate the acoustic performance of a cotton fiber absorbing material in comparison to a new polypropylene fibrous material, called ECOSORB ®. The acoustical evaluation was done using measurements of material properties along with sound pressure level from road testing of a fully-assembled vehicle. The new polypropylene fibrous material showed significant advantages over the cotton fiber materials in material properties testing and also in-vehicle measurements. In addition to the performance benefits, the polypropylene absorber provided weight savings over the cotton fiber material.

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.