The Mechanical Properties Of Adhesive Bonded Joints For Lightweight Automotives

In the development of automotive industry, lightweight design is an effective method to make car more fuel-efficient, safe and environmental. Lightweight design can not only improve the power performance and reduce the fuel consumption and gases emissions, but also can efficiently promote the stiffness and impact performance of bodies. To reduce the weight of automotives and efficiently utilize the advantages of different materials, such as aluminum, magnesium, Carbon Fiber-Reinforced Plastics (CFRP) and high strength steels, the advanced lightweight structure with different materials has been considered in the bodies of modern automotives. Particularly, the use of CFRP and metals is very popular. However, the joining of these materials is really challenging and it is impossible to join such different materials by using conventional techniques, such as electric welding. While adhesive bonding and mechanical connection is a good choice which can meet the requirements for the construction of lightweight structures. Particularly, adhesive bonding can enhance the corrosive resistance and increase the body stiffness. For improving the quality of joints and the performance of structure, the estimation and optimization of bonding properties for different joints are often required. Experimental and Numerical analysis by mechanical tests and finite element method are effective methods.In the current work, the bonding properties of two types of adhesive bonded joints, including single lap joints and T-joints which were made of steel, CFRP and aluminum, were investigated by experimental and numerical methods. Firstly, the bonding strength of the steel-steel and CFRP-steel joints was measured. Meanwhile, the influence of the lap lengthe, joining mode and joining materials on the bonding strength were clarified. The morphologies of fracture surfaces were also observed by scanning electron microscope. And then, by using ABAQUS code, the stress distributions for the steel-steel and CFRP-steel joints were analyzed. Results from numerical analysis were in good agreement with those of experimental work. This verified the feasibility of the using of FEM. Furthermore, the influence of overlap length on the stress distribution and bonding strength for the single lap joint was also carried out by FEM analysis. Finally, by applying the orthogonal experiment and controlling variable methods, the effect of joint stiffness, stiffness ratio on the bonding strength of T joints.