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Over the past several decades, significant gains in automobile fuel efficiency have been achieved through down-sizing, aerodynamic design and drive train improvements. As performance limits are approached in these areas, aluminum is being used to further reduce body weight by up to 40% compared to steel. In anticipation of the continued demand for more fuel efficient automobiles, aluminum sheet component unibody and extrusion and cast component space frame designs have been studied to address joining and structural performance. Joint geometries unique to specific body designs clearly illustrate the need for close linkage of the design and assembly functions. Joining and assembly methods that provide static and dynamic structural integrity, 15 to 20 year durability and that can be integrated into robust manufacturing systems are key to aluminum usage for auto body structure.

The need to substantially reduce the weight of automobiles to improve performance or meet CAFE requirements has led to an increased use of lightweight materials such as aluminum. To use aluminum efficiently in auto body structures, component and joint designs and joining methods are likely to differ from those traditionally used in steel bodies. With proper design, aluminum automotive frames can efficiently meet or exceed the performance requirements for stiffness, static strength, fatigue strength and crash performance. This paper presents some joint design concepts for aluminum frames and compares the performance of joining methods such as resistance spot welding (RSW), gas metal arc (GMA) welding, weld bonding, adhesive bonding, riveting and mechanical clinching for both unibody and spaceframe construction. Recommendations for preferred joining methods are also made based on the effect of design details on joint performance and assembly.

The use of polished aluminum fuselage skins has been a standard on U.S. commercial jet transport aircraft for decades. Increasingly stringent environmental regulations for paint stripping combined with fuel and maintenance savings allows consideration of flying polished non-painted aircraft. Boeing, McDonnell Douglas and Embraer currently manufacture commercial aircraft with polished alclad aluminum fuselages. Commercial airlines such as American Airlines, USAir, Eastern, Northwest and ASA fly non-painted fleets. These customers require the aircraft to be delivered with a polished appearance incorporating minimum fleet graphics. The manufacturing of polished aircraft requires unique production and handling procedures to fabricate all exterior panels with identical color match and reflectivity.