With the wide application of aluminum alloy in the automotive field, and the reduction of the cost of carbon fiber, the application of aluminum alloy and carbon fiber hybrid materials has become an important direction of the future development of automotive materials. The development of friction stir welding technology makes the connection between different materials easy to realize. In addition, with the development of hot forming technology of ultra-high strength steel and the reduction of hot forming process cost, hot forming products of high-strength aluminum alloy represented by 7075 aluminum alloy began to be applied in automobile industry.

As for the rear anticollision beam, with the increase of energy absorption requirement for low-speed collision, extruded aluminum alloy has been widely applied in the middle and high-end automobiles due to its low process cost. However, due to the limitation of extrusion process, the flexibility of extruded aluminum design is poor, which is not conducive to further lightweight. Therefore, the hot forming technology of 7075 high strength aluminum alloy is considered to further optimize the rear anti-collision beam.Based on friction stir welding prepared for mixed materials, designed four kinds of structure anti-collision beams, which were respectively made of 340LA steel, 6082 extruded aluminum alloy, 7075 hot-forming aluminum alloy and 7075 hot-forming aluminum alloy which patched with carbon fiber reinforced composite (CFRP) plate were designed for one car. In addition, the energy absorption box is designed with several kinds of materials, which were medium-strength steel, extruded aluminum, stamped aluminum and carbon fiber composite respctively. Based on the crash simulation analysis using LS-DYNA, deformation nephogram and curves of maximum invasion of four kinds anti-collision beams were obtained

The results of the intrusion of collider based on crash simulation in the rear low speed impact, indicated that four kinds of bumpers both met the collision requirements by optimizing the shape and size of the anti-collision beam and energy absorption box. Because of the creative using the technology of aluminum hot-forming, as well as friction stir welding of carbon fiber composite patch panel between aluminum plate, the weight of the anti-collision beam assembly was reduced from 4.82kg to 1.10kg, and the weight of this new anti-collision beam assembly mixed with 7075 aluminum and CFRP was 1.38 kg lighter than the 2.52 kg of 6082 extruded aluminum beam assembly. In addition, the results of energy absorption curves shown that the energy absorption box of the new anti-collision beam with has a higher energy absorption effect.

Dr. Eng. Zhimin Liu, BAIC Motor Co.Ltd., CHINA; Mr. Leigang Chen, BAIC Motor Co.Ltd., CHINA