A comparative study on energy absorption of flat sides and corner elements in CFRP square tube under axial compression

The cross-sectional configuration is one of the factors influencing the energy absorption performance of composite tubes under axial compression. Flat sides and corners are basic elements for the configuration. However, their contributions to the energy absorption have not been systematically compared. This paper presents a "press and cut"approach which allows to investigate the energy absorption of flat side and corner elements in a condition closely resembling axial crushing of a tube. Using this method, the crushing responses and energy absorption behaviors of flat side and corner elements in carbon fiber reinforced plastics (CFRP) square tube under axial quasi-static compression were investigated experimentally. The results showed that the corner elements had higher specific energy absorption (SEA) values than the flat side elements. The higher SEA value is attributed to the additional axial tearing fracture of the fronds developed at the corner and the suppression to delamination by the hoop tension force in the round corner. A modified analytical model based on Hussein's analytical model was established to predict the mean crushing force of the flat side and corner elements. Finally, axial crushing experiments were performed for CFRP tubes with a cross section consisting 12 corners. The 12-corner tubes exhibited an about 18% higher SEA value than the square tubes while a similar force.