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The Interference-Fit Bolted Joining of Hybrid Metal/Composite
Abstract:
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.