Folding or hemming is a technique to join two metal sheets and is commonly used in automotive industry for the production of doors and flaps. The outer sheet is folded around the inner sheet, while the outer provides a nice surface and the inner sheet creates the stability of the part. While using additional adhesive in the fold and a fine seam sealing it also provides a corrosion resistant joint. The problem with using an adhesive is the need of an additional process.
In this work the inner metal sheet is replaced by an organic sheet. Thermally assisted press joining is used to join the sheets. Here, the adhesive and the fine seam sealing are not needed anymore and the process can be simplified. Furthermore, the organic sheet increases the lightweight potential of the joined part. The aim of this study is to find the best process parameters and folding fillings. In figure 1 you can see the crosssections of a folded metal before and after the inductive heating showing that the fold can be fully filled by the “lofting” expansion of the organic sheet.

Figure 1: Crosssections of folds before (left) and after (right) the heating

In this systematic investigation, different samples are analysed with respect to the appearance and the pull-out properties of the folds. It has been observed that especially the force during folding, the heating time and the pretreatment of the metal have an influence on the maximum pull-out force and the work during pull-out.
We thank the Federal Ministry for Economic Affairs and Energy and the AiF for the funding of this project.