Analysis of Lightweighting Design Alternatives for Automotive Components

Gasoline-powered vehicles compose the vast majority of all light-duty vehicles in the United States. Improving fuel economy is currently a topic of great interest due to the rapid rise in gasoline costs as well as new fuel-economy and greenhouse-gas emissions standards. The Chevrolet Silverado is currently one of the top selling trucks in the U.S. and has been previously modeled using the commercial finite element code LS-DYNA by the National Crash Analysis Center (NCAC). This state-of the art model was employed to examine alternative weight saving configurations using material alternatives and replacement of traditional steel with composite panels. Detailed mass distribution analysis demonstrated the chassis assembly to be an ideal candidate for weight reduction and was redesigned using Aluminum 7075-T6 Alloy and Magnesium Alloy HM41A-F. Finite element analysis demonstrated that both the Aluminum and Magnesium configurations are feasible alternatives, allowing a weight reduction of 60% and 70% respectively of the original chassis design while reducing overall stress through the model and consequently providing a higher factor of safety. The truck bed and rear floor panels were redesigned using lightweight composite panels consisting of aramid/phenolic honeycomb cores with polyester/glass fiber face plates. The sandwich structures were modeled using LS-DYNA with two approaches. While both employ shell elements for the faceplates, the first simplifies the core using solid elements and the effective orthotropic material parameters while the second offers a more comprehensive depiction of the hexagonal core cells with shell elements. The dynamic behavior analysis of the composite panels incorporated into the Silverado model was also performed using LS-DYNA. When combined, aluminum chassis alternative with replaced composite panels offer a significant weight saving for the Chevrolet Silverado. Furthermore, the composite panels designed can be adapted for heavy-duty vehicles where a greater impact on fuel economy would be provided.