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Improving vehicle crash, NVH and metal fatigue performance using expanding polymeric foams can be achieved with a systematic approach. By employing a systematic approach with expandable epoxy foams and alternative carriers, the product development process can be significantly reduced. As a result, high strength and lightweight solutions can be designed to improve the structural performance of today's vehicles. This technical paper will examine the key steps in utilizing a systematic approach to selecting, designing and modeling structural expandable epoxy foam solutions used in conjunction with metallic and non-metallic carriers. A review of material properties, alternative designs and finite element modeling methods will allow for a thorough understanding of how expandable epoxy foams can meet the demanding challenges for improved occupant safety, reduced interior noise levels and increased durability at a reduced vehicle weight.

Under the constraints of improved vehicle refinement, automotive OEMs are challenged to improve vehicle noise, vibration and harshness (NVH) characteristics, reduce vehicle weight, and streamline manufacturing and assembly processes. In support of these objectives, alternate methods of vehicle noise control are being investigated. This paper will address one area where alternate material strategies are being investigated to meet these requirements. Floorpan damping treatments are a primary component of the overall vehicle noise package. This paper will investigate three floorpan damping treatments. Comparisons will be made between asphaltic melt sheets, constrained layer dampers, and spray-on dampers. Performance of these treatments will be measured using laboratory methods and will feature a case study using a Body-In-White (BIW) to demonstrate performance of the different materials.

A variety of expandable sealants are used to fill vehicle body cavities to impede noise, water, air, and dust from entering (and exiting) the passenger compartment. This paper compares three sealant technologies used for filling body cavities. The technologies are rubber-based elastomeric preformed parts; thermoplastic elastomeric preformed parts, and two-component polyurethane that is foamed-in-place directly in the vehicle body cavity. The following comparisons are made between the three technologies: application methods and issues, cost, material properties and acoustical performance.

Vehicles are faced with a variety of airborne and structure-borne noise sources, such as wind, road, tire, engine and powertrain. To minimize the noise intrusion into the passenger compartment, a system level approach must be taken. This system level approach requires a focused effort to minimize noise at the primary sources, and an engineering initiative to desensitize the transfer paths through proper body design, sealing, and the implementation of noise control materials. This paper looks at different innovative materials applied to the body structure, their design and placement of them to support a quiet interior. A series of vehicle case studies details the in-vehicle performance and benefits of both preformed and bulk material solutions that are applied to the body structure: baffles, sealers, barriers, dampers and structural reinforcements. An emphasis is placed on low cost, low mass and high performance optimized solutions.

Advances in the design and manufacturing of Expandable Epoxy Foam Inserts have resulted in a dramatic rise in the use of these technologies for the treatment of structureborne noise and vibration control. The evolution of these technologies has resulted in light weight and cost competitive solutions when compared to changes in primary body structure and surrounding sheet metal. These advances are discussed in detail. A structured, methodical approach to the identification of requirements for vehicle treatments is discussed. Based on these requirements, a process for the evaluation of application designs and the design optimization process are discussed. Validation of both the material technology and the engineering approach are presented through demonstration on actual vehicle applications.

Maintaining or improving acoustic and vibration quality of vehicles, the automotive industry continually faces design goals to reduce weight and manufacturing cost. In light of these objectives, advanced material design techniques facilitate the development of a high performance bulk applied constrained layer vibration damper aimed at improved automotive acoustics. The overall vehicle acoustic and vibration quality relies heavily on floor pan vibration dampers. A review of current industry damping technologies is addressed. Industry migration to bulk applied extensional dampers from the once ubiquitous asphalt sheet damper is discussed. Furthermore, this paper addresses the development of a new bulk applied constrained layer damper technology that delivers superior acoustical performance. The paper presents the chemistry formulation, the prediction of analytical results, and experimental validation.

A new semi-active damping approach for the reduction of transmitted acoustic noise is investigated. It involves the controlled variation of the system's spring constant in response to the system's motion in such a way as to maximize the energy lost in the damping elements. A Discrete Mechanics simulation of a prototypical spring-mass-damper system is used to compare the performance of this approach with the semi-active viscous damping approach being applied to this problem today. It is found that: (1) Parametric damping does not require precise phase matching between the noise signal and the response of the system. (2) “Runaway” catastrophes associated with the nonlinear response of the spring constant are avoided by saturating the response of the spring. (3) An algorithm that controls the response of the element by recognizing when it is storing undesired energy suffices to attenuate harmonic and transient noise below 1:1 transmissibility for all frequencies at and below resonance.

Cavity reinforcement materials are used in the automotive industry to stiffen hollow cavities in vehicle body constructions. Typical areas of use include the engine rails, rocker panels, roof support or any other cavity in need of structural reinforcement. Use of these materials can allow for significant reductions in vehicle weight and increase structural stiffness with minimal impact to production tooling. Additional benefits can be gained by using the material as a physical barrier to the propagation of noise, water and dust. The objective of this paper is to describe a case study which implemented a new type of cavity reinforcing material to improve low frequency vehicle noise and vibration characteristics.

Cavity reinforcement materials are used in the automotive industry to stiffen hollow cavities in unibody constructions. Typical areas of use include the engine rails, rocker panels, roof support or any other cavity in need of reinforcement. Use of these materials can allow for reductions in vehicle weight without sacrificing long-term durability and stiffness. Additional NVH benefits could be gained through the change in stiffness and through acting as a physical barrier to the propagation of noise, water and dust. The objective of this paper is to describe the properties of a new type of cavity reinforcing material and to identify key properties of reinforcing materials.

Chemically and heat reactive, expandable sealants are used as “acoustical baffles” in the automotive industry. These acoustic baffles are used to impede noise, water and dust propagation inside of structural components and body cavities. Use of these sealant materials has grown significantly as the demands to improve vehicle acoustic performance has increased. Various test methods have been developed to quantify the performance of these materials through direct comparison of material samples. These investigations use standardized testing procedures to characterize the acoustic performance of a material sample on the basis of controlled laboratory test conditions. This paper presents a step in the progression of evaluating acoustic baffle performance in the vehicle. Standard experimental techniques are used to investigate the influence of the baffles on the vehicle acoustic performance.