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Expandable cavity sealers have become a critical component of the overall acoustic package that contributes to the documented noise reduction in passenger car applications over the course of the last twenty years. They encompass a variety of technologies, some of which are delivered into the supply chain as bulk materials and others which are highly engineered parts and assemblies. As the market for smaller and more fuel efficient vehicles continues to expand, design architectures of the base vehicle platforms are evolving to include body designs with smaller spaces between adjacent layers of sheet metal. As this space, or cavity, between the adjacent layers of sheet metal is shrinking, the complexity of components that must be integrated into the space between these layers of steel is increasing. Complex arrays of airbags, corresponding wire harnesses, and water management tools are now standard requirements in the design process.

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.

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.

Finite Element analyses and tests are performed in order to verify appropriate use of material models to represent epoxy foam in FEA. Two types of material models are studied that utilize different approaches to model behavior of materials. One uses nominal stress/strain data to depict yield condition. The other uses plastic stress/strain data and von Mises type yield condition. Due to the particular and different behaviors of epoxy foam in compressive and tensile testing, material curves in both compression and tension areas are utilized. After validation of the material model in both compressive and tensile testing, three point bending tests and simulation of foam and composite beams are carried out. Simulations of material failure and interface effects are also discussed.

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.

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.

Driven by global pressures of weight reduction and cost savings, suppliers of specialty sealing and bonding products to the automotive industry have responded by expanding the focus of their product development activities. OEM engineering practices have brought about significant changes within the specialty sealing and bonding supply base. The successful suppliers in this market have responded to these pressures and initiated changes in the processes through which their materials are developed and released into production. In an industry historically populated by chemists and manufacturing process engineers, new requirements have led to an increase in application engineers and technical specialists, providing the necessary vehicle development expertise to the sealant industry. To support these expanded roles, new research and development facilities and associated advanced technologies have become a critical requirement.

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.

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.