Forming limit evaluation of adhesive bonded sandwich steel sheets and numerical prediction.

In the present work, the effect of hardener to resin ratio of epoxy adhesive on the formability of adhesive bonded steel sheets has been studied. Forming limit curve has been evaluated by hemispherical dome tests at predefined strain‐paths. They are predicted by finite element simulations using strain mapping method. Cohesive zone model has been used to model the interface between skin and adhesive core. An improvement in the forming limit of sandwich steel sheets has been observed when the hardener to resin ratio is changed from 0.6 : 1 to 1 : 1 due to the improved plasticity of adhesive core layer at 1 : 1 ratio as compared to others. The forming limit of sandwich sheet made at 1 : 1 ratio is equivalent to base steel sheet of same thickness and grade. This shows the potential use of sandwich sheet in place of base steel sheet. The forming limit curve predictions agree well with experimental data for base sheet, while reasonable agreement is observed in case of sandwich sheet. Numerical prediction of interface delamination show insignificant influence of hardener to resin ratio on the onset of delamination and significant effect of strain‐paths. [ABSTRACT FROM AUTHOR]