Gradually collapsible crash boxes with bonded aluminium tubes

In this study, a novel crash box idea was presented, including a step-by-step collapsible structure by joining coaxial tubes with gradual bonding surface areas. This telescopic crash box absorbed impact energy by sequentially fracturing the adhesive interfaces from the top tube to the back tubes. In each bonding interface fracture, a certain amount of the impact energy was reduced. These gradually broken adhesive bonds and subsequent movement of the coaxial tubes were increased pedestrian safety by producing fewer impact forces and adding more braking time. Due to the just adhesive joints break after small hits, a broken crash box can be repaired easily by bonding coaxial tubes. Validation of the design was performed using the Finite Element Simulations by parametric modelling of the representative design of crash boxes with frontal impact simulations of a vehicle. Transmitted forces to the vehicle body were obtained according to impact duration. Impact energies were obtained by calculating the area under impact of force–displacement curves. The optimal size of the coaxial tube bonding interfaces and the number of the telescopic tubes were obtained for maximum energy absorption comparing with conventional crash boxes.