Thin-walled square columns are generally used as impact energy absorber in automotive structures
due to their ease of fabrication and installation, high energy absorption capacity in terms of
progressive plastic deformation and long stroke. However, the main drawback of standard square
column is the high initial peak force. An external tapered plunger is proposed to overcome this
shortcoming while at the same time, improving the impact performance. Static and dynamic axial
crushing were performed by theoretical and finite element analysis to determine the initial peak
force (IPF), crush force efficiency (CFE) and plastic specific energy absorption (SEA) of columns
with external plunger of various taper angles. The simulations results were validated by
experiments. It was found that the external plunger significantly enhanced the column impact
performance and the deformation characteristics as well. Comparison with plain square column was
carried out and it was found that the concentric plunger reduced the initial peak force and increased
the crush force efficiency for both static and dynamic loading conditions.