Development of a hybrid crash-relevant car body component with load-adapted thickness properties: Design, manufacturing and testing

Semi-finished sheet products with load- or forming-adapted properties are classified as tailored blanks. By locally adjusting sheet thickness or material properties, the overall performance of the component can be improved while reducing the weight of the part. State-of-the-art tailored blanks are realized by rolling, welding or tailored heat treatment of monolithic materials and consider a change in properties with respect to the sheet plane. A further weight reduction could be achieved by combining the idea of tailored blanks with a multi-material design approach along the sheet thickness. For this purpose, a top-down material design is proposed to allow a demand-oriented hybrid tailored stacked blank design. Within this contribution an optimization-based top-down design methodology is applied on a crash relevant car body part. Based on benchmark crash simulations of a reference BIW structure, a critical body component is determined. The identified demonstrator component is later subdivided into multiple layers and submitted to an optimization loop in which the developed methodology varies the material parameters for each single layer. The result is a tailored stacked hybrid blank consisting of steel and FRP layers. In order to meet formability restrictions of the novel semi-finished product, the part under investigation is redesigned and compared with the reference BIW structure. Finally, the hybrid component is manufactured and tested on a dynamic crash device. Compared to a monolithic DP800 component, a mass reduction of 22% was achieved.