Användbarhetsutvärdering av det lätta sandwichmaterialet Hybrix för bilkarossapplikationer
This M.Sc. thesis is a material application evaluation commissioned by the advanced body engineering department at SAAB Automobile AB. The purpose of the thesis is to evaluate implementation of the innovative sandwich design material Hybrix into an automobile body. Today the most commonly material used in the body is galvanized steel sheets and by shifting material to Hybrix several problematic issues have to be dealt with. Hybrix is an innovative sandwich sheet that inherits thin stainless steel face sheets and a stainless steel fibrous core. The focus during the project has been to investigate problems concerning joining techniques, corrosion and noise and vibration behavior. To get a grip of what might cause problems a thorough pre study on each of the three areas has been carried out. To determine specific matters that concerns components in the body two specific components were investigated, these were the rear floor and the dash panel. Resistance spot welding is the most commonly used joining technique in the body, therefore a spot weld test was carried out on Hybrix. To determine the quality of the welds post weld material tests were conducted. The biggest corrosion issue was stated to be galvanic corrosion due to the dissimilarity in nobility between galvanized steel and Hybrix. This resulted in proposals of alternatives to spot welding where the Hybrix component would be electrically isolated from surrounding body work to avoid galvanic cells to be formed. The most suitable joining technique proposed is Eckold clinching combined with adhesive. Weld studs on the dash panel can be attached to the Hybrix component by welding the stud to a console that can be joined to the dash panel with double adhesive tape. The components are formed through deep drawing and it is not possible to simulate deep drawing of Hybrix as of today. The weld tests clearly show that the weldability of the combination of Hybrix and galvanized steel is very poor. This means that some alternative for spot welding must be used. It is concluded that the weldability of Hybrix and galvanized steel is very poor and that the galvanic corrosion issue can be solved by electrically isolating Hybrix. It is also concluded that tests within the areas of noise and vibration, forming and Eckold clinching has to be conducted.