Fimcar – Influence of Seas on Frontal Impact Compatibility

The aim of the FIMCAR project (Frontal Impact Compatibility and Assessment Research; co-funded by the European Commission within the 7 Framework Programme) was to develop and validate a frontal impact assessment approach that considers self and partner protection. Regarding the results of the FIMCAR accident analysis, one major issue of frontal impact compatibility is structural interaction. Not all car types have the potential to align their Primary Energy Absorbing Structures (PEAS) with the common interaction zone proposed by FIMCAR. Some cars use Secondary Energy Absorbing Structures (SEAS) to interact with external structures and thereby improve the structural interaction. There is a challenge to evaluate the different structural concepts, and in particular SEAS, in the possible variations of potential impact combinations. The main objective of this study is the identification of characteristics of appropriate SEAS. Therefore this paper will give an overview about the investigations done within FICMAR to analyse parameters which improve the car-to-car crash performance. As part of the analysis physical test data as well as simulation results were used to study the interaction of the front end structures. Within FIMCAR 10 car-to-car tests were conducted. The main outcome was that the alignment of the PEAS of both crash partners is crucial for the structural interaction. Furthermore the crash test showed that misaligned vehicles perform better if they are equipped with appropriate SEAS than vehicles without a lower load path. These investigations were supported by numerical simulations. Within the FIMCAR project, amongst others, FEM vehicle models called Parametric Car Models (PCMs) were used for the assessment of car structures. For this study they were supplemented by the detailed FEM models provided by NCAC. For the SEAS analysis the PCMs were used to create several geometrical modifications. Due to the simplified design of the models the influence of the crash performance could be correlated well to the design of the SEAS. The analysis of the simulations identified 3 geometrical parameters of the SEAS that had a positive influence in a car-to-car crash. The first parameter is the longitudinal position of the SEAS. A position of about 230mm behind the bumper beam (or further forward) improved the crash performance of both collision partners. The second parameter is the vertical connection between SEAS and PEAS. A robust connection located about 250mm behind the bumper beam was able to activate the penetrating structures of the striking vehicle and therefore to improve the structural interaction. The third geometrical parameter that was identified is the height of the cross section of the cross beam of the SEAS. An increase of the height by 50% to 60mm showed that the SEAS was able to support the penetrating structures better than the small SEAS. According to the capabilities of assessment procedures to assess appropriate SEAS the OverRide Barrier (ORB), test configuration as well as the full width assessment metrics developed within FIMCAR were checked. The ORB test was not able to discriminate between appropriate and inappropriate SEAS. Regarding the full width test the Full Width Rigid Barrier (FWRB) configuration was not able to detect and assess the SEAS structures mainly due to the very short assessment interval, too. In contrast the Full Width Deformable Barrier (FWDB) was able to detect and correctly assess the SEAS that improved car-to-car crash performance due to their longer assessment period.