From Bridge to Bumper: Utilization of Pre-stressing During Manufacturing of Hybrid Sheet Metal Structures

Pre-stressing is often used in civil engineering to increase the load-bearing capacity of bridges and buildings. In order to exploit this potential in sheet metal required. Therefore, an approach to join and pre-stress fiber-reinforced plastic (FRP) straps and sheet metals during a forming process is proposed. The FRP strap is placed around two collars drawn into the sheet. A punch plastically expands the collar, while the FRP strap is elastically elongated, resulting in beneficial pre-stresses after unloading due to the different spring-back. In this paper, the predominant mechanism is verified and parameters influencing the pre-stress are identified by experimental and numerical investigations. The hypothesis is investigated that a customized pre-stress and thus a higher strength during the structure’s usage can be controlled by varying the collar’s expansion. Possible applications include bumpers and side-impact beams.