Hemming of layered composites dedicated to stiffness increase

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Aluminum/polymer/aluminum composites do show advantages compared to monolithic materials when strength, stiffness and damping characteristics are set to a global optimum. Although their mechanical properties have been improved during recent years, application of such hybrid materials in automotive industry is not well-established due to unsufficient knowledge about its forming characteristics (e.g. in table-top hemming). This paper deals with challenges of delamination of stiffness increasing composites in industrial table-top hemming processes.

Stiffness increasing composites are consisting of two aluminum sheets and a viscoelastic damping layer: The inner sheet includes stamped beads and increases the stiffness while the outer sheet is set up as cover sheet. The main concern is delamination behavior in flanging, pre-hemming and final hemming used in real components consisting of those layered materials. In this investigation hemming parameters were varied, e.g. flanging radius, bending direction and level of pre-strain. Additionally, surface quality of the hemming rope is evaluated dedicated to delamination after each process step. Computer tomography investigations were used to identify different zones of delamination within the hemmed flange area.

 


Prof. Dr.-Ing. Dr. h. c. Mathias Liewald MBA
Dipl.-Ing. Dennis Hofmann1
Dipl.-Ing. Severin Hönle

Institute for Metal Forming Technology, University of Stuttgart, Holzgartenstr. 17, 70174 Stuttgart, Germany
1 Corresponding author
Telefon: +49 (0)711/685-83824
E-Mail: dennis.hofmann@ifu.uni-stuttgart.de