Abstract

The transition from combustion engine vehicles (CEV) to battery electric vehicles (BEV) generates new challenges for the design process of crash management systems (CMS). The absence of supporting sub structures, like the engine, in combination with the diversity of the vehicle mass due to different types of batteries provide various boundary conditions and load scenarios. One approach to overcome the new challenges for CMS is the usage of hybrid structures made of metals supported by short or long fiber-reinforced polymers (SFRP/LFRP). In particular, the usage of chopped LFRP, like sheet molding compounds (SMC), allow for a cost-efficient production while keeping flexibility in the design of complex structures. In addition, SMC materials have an excellent weight to strength ratio. The SMC, consisting of a thermoset resin matrix including filling material and the reinforcing copped fibers, is manufactured in a compression molding process, whereby the final structural properties of the component arise through the manufacturing process itself. Consequently, manufacturing effects such as fiber-matrix segregation may lead to an inhomogeneous fiber matrix distribution and fiber orientation. Both have a major influence on the structural performance and need to be considered in a structural analysis. Apart from cost-efficient production, new materials and their combinations also demand the virtual design of new structures by numerical simulation. While a profound knowledge exists for the structural simulation of metal components, uncertainties are reality for the description of hybrid joints and on the effective mechanical behavior of SMC parts. In this regard new methods for the virtual design of hybrid structures are developed. They cover the complete chain from the design of the manufacturing process, to the actual production of parts and finally the assessment of the structural performance. The present contribution will focus on the virtual prediction of the mechanical behavior of the SMC, based on data defined by the manufacturing process. Here, the key information (fiber orientation, fiber distribution, fiber volume content) is extracted from a micro computed tomography (µCT) analysis. In combination with experimental data obtained from mechanical tests of the pure matrix material and from SMC coupon tests under various loading conditions, the parameter of the numerical model are determined. The calibrated material model is subsequently validated by a test series of SMC honeycombs and the results as well as numerical influences are discussed.