Structural optimization of automotive body components based on parametric solid modeling

Parametric modeling was used to build several models of an automotive front structure concept that utilizes carbon fiber composite materials and the corresponding molding processes. An ultra-lightweight aluminum body front structure was redesigned to include an all-composite front structure. Two alternative concepts were studied which represent the structure as a bonded assembly of shells. Closed sections result from two pieces - an inner and outer. Parametric modeling was found to be a useful tool for building and modifying models to use in optimization concept studies. Such models can be built quickly and both the sketch dimensions and location dimensions are particularly useful for making the adjustments necessary to fit the various body pieces together. The parametric models then must be joined together as one geometric solid model in order to obtain a surface mesh. Structural optimization input data can then be seamlessly and quickly created from the parametric-model-based finite element model to begin the tradeoff studies. This integrated process in which parametric modeling was couple with structural optimization was used to carry out design studies on the lightweight body front structure. Several carbon fiber material combinations were studied to determine mass reduction potential of certain types of carbon fiber products considered to be lower cost than typical carbon fiber materials used in the past. Structural optimization was used to compare several composite constructions for the design of the bonded front structure. Eight cases were studied using various materials and composite lay-ups. Mass savings estimates from 45-64% over steel were obtained. The most reasonable design consisted of a combination of relatively low cost chopped carbon fiber and woven carbon fiber an using a 20 mm balsa core in the top of the shock tower area. This design had a maximum thickness of 7 mm and a mass reduction over steel of approximately 62%.