Experimental investigation on failure mechanisms of hybrid steel/GFRP hat-shaped beams under bending loading

The bending failure mechanism and energy absorption characteristics of hybrid metal/composite structures are the keys to the side collision safety of automobiles. The purpose of this paper is to investigate the bending behavior and failure mechanism of hybrid Steel/GFRP hat-shaped beams under three-point bending. Firstly, both quasi-static and dynamic three-point bending tests were conducted on Steel, GFRP and hybrid Steel/GFRP hat-shaped beams. Then, the effect of layups and loading speeds on the bending failure behaviors of GFRP hat-shaped beams were investigated, and the five stages of the bending process of GFRP hat-shaped beams were exposed. Finally, the failure mechanism of hybrid Steel/GFRP hat-shaped beams under both quasi-static and dynamic three-point bending were investigated. It is found that the failure mechanism is related to the interaction effect between the Steel and GFRP parts in the hybrid Steel/GFRP hat-shaped beam. In the bending failure process, the crack propagation in GFRP parts is delayed by the plastic deformation of the connected Steel parts, which improves the energy absorption and load carrying capacities of the hybrid Steel/GFRP hat-shaped beam, and this improvement in the whole bending process is quantitatively exposed in this work. Besides, it is found that with the same impact energy, the load carrying capacity of the hybrid Steel/GFRP hat-shaped beam can be increased by the loading roll diameter increasing.