SAE International The Interference-Fit Bolted Joining of Hybrid Metal/Composite 2012-01-1867

Joints represent potential weak points in the structure, the design of the overall structure tends to follow from the design of the joint. To date, metal/composite joints are general in current aircraft structure. Some of the reasons for lower joint efficiency in composites are: brittleness which means little stress relief around the highest loaded holes, anisotropy which leads to higher stress concentration factors, low transverse strength, susceptibility to delamination, and sensitivity to environmental conditions. All of these factors together with the complexity of composite failure modes make the analysis and design of composite joints far more complex than that of metallic joints. Fatigue failure is the root cause which makes aircraft unserviceable. 75-80% of fatigue failures occur in the joints of structure, therefore researching joints is very important for improving aircraft life. Much effort has been put into solving the technical challenge for composite bolted joints. In this study the interference-fit bolted joining of composite/metal hybrid has been studied. Composite and metal plates were purchased and clipped. Fasteners for interference-fit were manufactured, and the methods of drilling were researched. Composite/metal hybrid joints with different interference were manufactured by electromagnetic riveting technology. Then fatigue test of these joints were carried out. The test results presented in this paper indicated that suitable interference can improve the fatigue life of composite/metal hybrid joints. Interference of 0.5%~1.5% is more suitable for composite joints and 1.5%~2.5% can all improve metal/composite joints fatigue life more than doubled.