Influence of Materials and Joints on the Reinforcement of Frontend Systems

Euromotor 'New Advances in Body Engineering',
7th and 8th December 2000, Aachen

Dipl.-Ing. T. Parr

Abstract:

The number of modular front end systems in automotive applications has highly increased in the past encouraged by changing requirements on the vehicle front structure. At present a variety of designs in different material qualities is in use. Metallic carrier structures are used due to the achievable component stiffness and strength. Carrier constructions based on polymer materials offer a higher integration potential compared to all metal solutions but thereby need reinforcing elements for the main load paths between the linking points of the body. The reinforcement of polymer carrier structures can be realized by different concepts for the creation of new load paths. These can be integrated in the polymer component structure by sheet metal belts. For the metallic reinforcement, belts in form of flat sheet-metal strips are used. At variant 1 a belt is used which is placed in the upper area of the structure, while at variant 2 a belt with the shape of a semi-bow around the side member connections is applied. The combination of both possibilities is considered to be the third variant of the component reinforcement in the upper region of the front end carrier. The reinforcements between the connecting points at the steel sheets realize load paths between these linking points. These are located in transversal vehicle direction in the upper area of the front end structure. The structure passes the loads on to the adjacent body-in-white structure in case of collisions. The analysis of the different concepts shows, that the reinforcements enlarge the load carrying ability in the described area. The reinforcements lead to a more ductile failure behaviour of the complete component, caused by the material characteristics of the metal. The results presented are standardized for an easier comparison on the maximum deceleration and intrusion of the impactor at impact on the unmodified component. With increasing stiffness of the structure the intrusion of the impactor is reduced significantly. The variants 1 and 3 show a uniform tendency at all load cases, while variant 2 fails at middle loads in an unfavourable way. The reinforcement of variant 3 leads to a significant lower intrusion in comparison to variant 1. Especially of advantage is the support in the area of the headlight attachment at variant 3, because of the reinforcement with two load paths. This prevents a buckling of the structure. In the future, further research is scheduled on reinforcement strategies for front ends under consideration of the vehicle body-in-white.