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Joining dissimilar parts in automotive interior trim applications has been accomplished by utilizing mechanical fasteners, organic and water based adhesives, and more recently, thermoplastic polymers. Recent trends towards reducing solvent emissions and waste management problems, improving the consistency of adhesive application, integrating parts, lowering parts fabrication costs, and designing a specified bond level has increased the use of thermoplastic adhesive films as bonding agents in several applications. Initial efforts began over fifteen years ago with Dow Adhesive Films (DAF) being designed for bonding interior trim fabrics to various substrates. Films have subsequently been designed to improve performance of many interior trim parts in many ways such as: improving water resistance, allowing the part to be molded before installation, imparting a slip surface to a part, and supporting a non-woven fabric.

The construction of most automotive interior headliners requires an adhesive material to bond polyurethane foam-backed fabric to a molded headliner shell. More than ten years ago, The Dow Chemical Company qualified and began supplying a thermoplastic adhesive polymer film for headliner applications which replaced wet adhesive systems at several fabricators. DAF 899 adhesive film has gained acceptance in the industry due to excellent performance, convenience, and cost effectiveness without additional waste handling or volatile organic emission concerns. Recent advancements in headliner design such as additional recessed areas with more demanding contours, new substrate materials and the desire for more efficient operations created an opportunity to design improved adhesive films to meet the emerging industry demands.

Adhesive materials are required to bond cover fabrics to most molded interior headliner substrates. Several thermoplastic adhesive films are qualified and used at U.S. and Japanese OEM's. These adhesive films offer benefits such as convenience, cost effectiveness, excellent adhesive performance and process efficiency while reducing concerns of emissions and hazardous waste handling compared to prior bonding methods. The automotive headliner part is a multifunctional component of the vehicle's interior trim. One of the main headliner functions is to reduce the interior cabin noise. Various adhesive materials are used in a lamination process to form a composite headliner. The purpose of this study was to compare the effects of this lamination process and various alternative adhesive materials on the overall acoustical performance of the headliner composite. Various headliner samples were fabricated under controlled process conditions and tested by an independent acoustics testing lab.

Fast, accurate delivery of metal to the shot well is critical to the success of any cold chamber die casting operation. For some metals this is a simple problem to solve. Magnesium, however, requires more innovative thinking. Simplicity of design is essential for reliable operation in the environment of a magnesium die casting facility. Complex control is required to provide speed and accuracy of shot delivery. Blending these two ingredients to produce a viable system produces a truly innovative shot delivery system for magnesium. Construction details of a newly developed stand alone system for the auto ladling of magnesium will be presented. Data with regard to speed and accuracy will also be presented.

The magnesium alloy AE42 (nominally a 4 % aluminum, 2 % rare earth alloy of magnesium) is a developmental die cast alloy with good strength and creep resistance at elevated temperatures. Standard salt spray corrosion tests have been used with controlled purity AE42 die castings to define the critical iron, nickel and copper contaminant levels below which excellent corrosion performance can be obtained. As previously observed with the magnesium alloys AZ91, AM60, and AS41, the critical iron content is dependent upon the manganese content of the alloy. While the iron:manganese tolerance for AE42 is about the same as that of AM60, the tolerance for the nickel and copper contaminants is greater than that of AZ91. When each of these contaminants is less than the critical level, the salt spray performance was equal to or better than die cast 380 aluminum and cold rolled steel.

A method for refining magnesium scrap which produces consistent, high quality magnesium metal has been developed. High quality magnesium metal is defined in this paper as metal which has heavy metal contaminants controlled within high-purity ASTM chemical specification, and is relatively free of internal impurities such as non-metallic inclusions (oxides and flux) and dissolved gas. The refining process utilizes a protective gas atmosphere, inert gas sparging and filtration techniques, rather than salt based fluxes, to remove both non-metallic inclusions and dissolved gases. Experimentation results of this refining process indicate magnesium scrap can be remelted and refined to a quality equal to or better than virgin ingot, without the introduction of salt based fluxes or a large capital investment.

Continued development of Reinforced Reaction Injection Molding (RRIM) polyurea polymers for toughness, blister resistance and large-part processing as exterior vertical body panels has launched ELPO-compatible exterior outers into automotive assembly-line operations. This allows automotive OEM design to take advantage of the unique molding shapes for side outers and fenders while reducing weight, assembly (DFA) and time/operations costs (DFM). Polyurea RRIM body panels have been successful in meeting the demanding auto industry requirement for lightweight, damage-resistant exterior outer panels as an economical alternative to steel. Design freedom advantages, low prototype cost and tooling savings through predictive modelling have allowed the commercial use of RRIM body panels. This high-temperature-resistant polyurea RRIM composite allows on-line painting, including passing through the steel corrosion protection primer (E-coat) cure environments.

The objective of this paper will be to review a novel recycle process involving Structural Reaction Injection Molding(SRIM) which enables a variety of coarsely ground plastic recycle materials to be incorporated into the molded part. What makes this approach novel, is that flexural modulus of the fabricated parts are actually increased when the recycled granulate is employed in the part. This paper will present data for the recycle of a variety of automotive parts, including painted fascia, door skins, covered interior door panels, armrests and instrument panels along with composite bumper beams into the SRIM recycle core process. Resulting part economics will be reviewed along with potential applications to utilize this technology.

The relationship between hydrogen gas and microporosity in magnesium alloy AZ91 was quantified, refuting the belief that hydrogen levels less than the maximum solid solubility are of no detriment. Sand castings were made from melts containing measured levels of hydrogen gas, and the amount of porosity was determined by density measurements. At concentrations below the maximum solid solubility, it was established that the amount of microporosity is directly proportional to the gas content. This supports the premise that dissolved hydrogen gas provides nucleation sites for microporosity, and that it is useful to remove all gas to achieve porosity-free cast parts.

The market for composite engine oil sealing components, such as valve covers and oil pans, continues to expand, replacing traditional metal stamping and die casting materials. As the market for these composite components grows, so must the understanding of the material performance characteristics and the relationship of these characteristics to the design of the part. Unlike metals, composites are viscoelastic in nature, exhibiting time-temperature dependant properties. Therefore, the traditional design approach utilizing static property data to predict long-term performance under load and over a wide temperature range will not sufficiently characterize the nonlinear property response of polymeric-based composites. A robust composite sealing design requires complete materials characterization, including long-term creep performance as a function of temperature, loading, and cycling.

The use of low density reinforced Reaction Injection Molded (RIM) substrates for covered interior automotive articles continues to increase globally. Reduced party mass, consolidation of manufacturing steps (labor), and the use of aluminum tooling, instead of steel, are cited advantages that LD-RIM offers when compared to traditional wood based and thermoplastic materials. Two RIM processes are successfully being used to produce covered interior door panels. Low density structural RIM (LD-SRIM), utilizing conventional RIM equipment, involves the placement of a pre-cut fiberglass mat in the tool cavity prior to open-pour injection of the 2-stream liquid urethane components. Low density reinforced RIM (LD-RRIM), utilizing lance cylinder RIM equipment, incorporates reinforcing fibers, such as milled fiberglass or wollastonite, in the liquid resin component. The liquid resin containing reinforcing filler is injected with the isocyanate component into a closed mold.

The opportunity for composites in engine closure systems such as valve covers, oil pans, and timing belt covers is expanding rapidly. The primary driving forces are lighter weight finished components, integrated designs, improved isolation of engine noise, improved materials systems, and matured manufacturing processes for composite materials. Thermoset-based composite materials, particularly those based on high-temperature resistant epoxy vinyl ester matrices, offer improved performance with respect to thermoplastic and thermoset polyester-based composites and can be manufactured using different processing methods. This paper presents the current state-of-the-art design, engineering and optimization techniques for engine closure systems. The performance requirements of different systems such as valve covers and oil pans are explained in detail. Techniques for long-term structural stiffness evaluation, vibration performance assessment and noise transmission estimation are described.

Structural instrument panels are an excellent alternative to traditional constructions since they can provide substantial part consolidation, weight reduction, tool and cost savings, and manufacturing and assembly simplification. In structural panels, the main energy absorbing element for decelerating an unrestrained occupant is the plastic integrated retainer-structural duct. The role of the components in the instrument panel needs to be clearly understood for adequately engineering the system and properly selecting the polymeric material for optimum system performance in the different operating environments. The present paper discusses the performance of the structural instrument panel, the engineering and design requirements, and provides guidelines for selection of materials.

Today's interior systems design engineer has been challenged with providing significantly lighter, simpler and more cost-effective instrument panel (IP) design solutions, while simultaneously meeting rigorous occupant protection and quality standards. These issues provided the motivation behind the fully-integrated structural instrument panel design developed for Chrysler's Dodge Dakota Truck Platform. This total system design approach greatly depends on the stiffness and ductility of the engineering thermoplastic substrate and cross-sectional design for managing the energy of unrestrained occupants during frontal collisions. The structural IP consists of a fully integrated, three-piece monocoque thermoplastic structure that replaces the traditional retainer, air delivery ducts, steel beams and reinforcements typically used in IP designs.

Increased requirements for crash energy management in automotive interiors have led to increased application of magnesium alloy AM50A. Successful integration of this new alloy with hot chamber diecasting process technology requires substantial adjustment and attention to processes and practices. This paper details the conversion of magnesium AZ91D steering column diecastings to high ductility structural alloy. Description is given of the changes made to foundry practices, casting parameters, process compliance monitoring, and hot end component management. The resulting improvements allow production of components comparable to the traditional alloy in manufacturing process demands while offering improved ductility and impact strength.

The increase in instrument panel design and functional performance requirements has resulted in a variety of structural architectures that have been utilized in different passenger vehicles, vans, and light trucks. Each architecture can be designed and engineered to meet corporate and federal requirements using different levels of integration, functionality consolidation, and assembly simplification. The present paper reviews three basic IP design architectures, i.e., traditional, hybrid, and structural, and discusses the performance requirement-functionality matrix in each case. Emphasis is given at explaining the role components play in the different architectures, defining their contribution to static, dynamic and crash performance and their relation to the overall assembly process and sequence. Performance and functionality requirements are linked to basic material characteristics that guide material selection for achieving design targets.

The effect of non-metallic inclusions (NMIs) on the properties of die cast magnesium was investigated. NMI content was quantified by a newly developed light reflectance technique. The mechanical properties of optimized AM60B test bars were found to decrease at high inclusion levels. Low inclusion levels did not statistically reduce the mechanical properties of AM60B as compared to virgin metal. Argon-refined AM60B displayed mechanical properties that were indistinguishable from virgin alloy. AZ91D test plates were die cast at various cleanliness levels. After salt spray testing, it was found that the surface quality of the castings was slightly degraded at high NMI levels. The general corrosion performance was also affected, but paint adhesion was relatively unaffected. At high NMI levels, the corrosion performance was still better than 380 A. Machinability of the AZ91D test plates was quantified by measuring tool wear and cutting forces.

Syndiotactic Polystyrene (SPS) is a new semi-crystalline polymer under development by Dow Plastics. The material is completely different from conventional styrenics in structure, physical properties and synthetic method, and represents the basis for an entirely new family of materials based on crystalline polystyrene. SPS has a melting point of 270°C (520°F) combined with excellent resistance to moisture and automotive fluids. Additionally, SPS products exhibit exceptional electrical performance and competitive toughness and stiffness. A wide range of products have been formulated for specific applications including impact-modified and glass-reinforced grades. This paper was designed to discuss the performance attributes of SPS as they relate to use of this material in automotive, interconnect systems where a combination of heat resistance, chemical resistance, dimensional stability and enhanced processability are required.

Standard salt spray corrosion tests have been used with controlled purity AM60 castings to define the critical iron, nickel, and copper contaminant levels below which excellent corrosion performance can be obtained. As previously observed with the AZ91 alloy, the iron solubility and the corrosion tolerance limit for iron are dependent upon the manganese content of the metal. The zinc free AM60 alloy has a somewhat lower tolerance for all three of the critical contaminants when compared to AZ91, but when the three contaminants are below their individual tolerance limits, the salt spray performance is again equal to or better than die cast 380 aluminum and cold rolled steel.

Relative advantages and disadvantages of blow molding vs. injection molding as they pertain to the production of automotive instrument panels are compared. Specific design issues such as parts consolidation and surface appearance are discussed, along with such processing issues as cycle time, tooling costs and regrind generation. In addition, an economic model is presented which examines the sensitivity of part cost to such variables as capital required, tooling cost, cycle time, finishing costs, regrind generated, and yearly volume of parts produced. The result is both a qualitative as well as quantitative tool to aid the designer and manufacturing engineer in making a rational process selection.