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Automotive manufacturers are being challenged to come up with radical solutions to achieve substantial (30-35%) vehicle weight reductions without compromising Safety, Durability, Handling, Aero-thermal or Noise, Vibration and Harshness (NVH) performance. Developing light weight vehicle enablers have assumed foremost priority amongst vehicle engineering teams in order to address the stringent Fuel Economy Performance (FEP) targets while facilitating lower CO2 emissions, downsizing of engines, lower battery capacities etc. Body sheet metal panels have become prime targets for weight reductions via gage reduction, high strength steel replacement, lighter material applications, lightening holes etc. Many of these panel weight reduction solutions are in sharp conflict with NVH performance requirements.

Advances in computerized solid modeling techniques allow the realistic representation of exterior body panels as solid models, at the concept stage of part design. A flow chart of the process is presented on the use of solid models to create exterior body panels. The flow chart allows a study of the process and is extended to the next generation of capabilities.

A computer-controlled body panel testing machine has been used to quantify stiffness and dent resistance of body panels at Chrysler. The influence of yield strength and local reinforcement on the mechanical behavior of automotive door panels has been investigated. Medium strength steels in the range of 210 -240 MPa yield strength have produced significant improvements in dent resistance over a 160 MPa yield strength steel. Considerable improvements in dent resistance can also be attributed to the use of local, adhesively attached, glass fiber reinforcement patches. The effects of boundary conditions and panel shape on stiffness and dent resistance are illustrated in this application.

Resin transfer molding (RTM) is the process of choice for the Body Panels of the Viper Sports car. The objective of this paper is to outline the reasons for the choice of RTM, and discuss development of technology for Class A surfaces and the paint system. Accomplishments to date and finally the work yet to be completed will also be defined. Conclusions from the work to date indicate that the RTM process enables a reduction in vehicle development time through faster prototypes and tool build times and that high quality, Class A surfaces can be successfully achieved even with epoxy tools. Additional work is ongoing to reduce cycle times and finishing costs, and to improve the in-process dimensional stability.

Resistance to dents and dings, caused by plant handling and in-service use, is generally recognized as an important performance requirement for automotive outer body panels. This paper examines the dent resistance improvements that can be achieved by maximizing surface stretch, through adjustments to the press settings, and substitution of a higher strength steel grade. Initially, the stamping process was optimized using the steel supplied for production: a Ti/Nb-stabilized, ultra low carbon (ULC) grade. The stamping process was subsequently optimized with a Nb-stabilized, rephosphorized ULC steel, at various thicknesses. The formed panels were evaluated for percent surface stretch, percent thinning, in-panel yield strength after forming, and dent performance. The results showed that dent resistance can be significantly improved, even at a reduced steel thickness, thus demonstrating a potential for weight savings.

In recent years, strict weight reduction targets have pushed auto manufacturers to use lighter gauge sheet steels in all areas of the vehicle including exterior body panels. As sheet metal thicknesses are reduced, dentability of body panels becomes of increasing concern. Thus, the goal becomes one of reducing sheet metal thickness while maintaining acceptable dent resistance. Most prior work in this area has focused on quasi-static loading conditions. In this study, both quasi-static and dynamic dent tests are evaluated. Fully assembled doors made from mild, medium strength bake hardenable and non-bake hardenable steels are examined. The quasi-static dent test is run at a test speed of 0.1 m/minute while the dynamic dent test is run at a test speed of 26.8 m/minute. Dynamic dent testing is of interest because it more closely approximates real life denting conditions such as in-plant handling and transit damage, and parking lot damage from car door and shopping cart impact.

One solution to the problem of spiraling automotive weights is the substitution of thinner high strength steels or thicker aluminum alloy outer body panels. In doing so the dent resistance of these panels must not be sacrificed. This study investigates the dent resistance of doubly curved rectangular panels in various steels and aluminum alloys. Dent depth on the order of magnitude of the panel thickness was studied. An empirical equation is developed that relates dent resistance to the yield strengths, metal thickness, and panel geometry.