Influences of assembly parameters on the strength of bolted composite-metal joints under tensile loading

Different assembly parameters, which include the bolt's clamping forces and bolt-hole interference fit conditions, can change the mechanical behaviours of the bolted composite joints under tensile loading. Three-dimensional finite element models with different bolt-hole fit conditions and bolts' preloads are constructed based on the contact relationships between the fasteners and the plates, the progressive failure features of composite materials and the elastic-plastic property of the titanium alloy. The models are used to study the effects of the assembly parameters after the modelling method is validated through comparing with test results. Through the analysis of the results, the conclusions can be drawn that: firstly, appropriate preload or interference fit can change the contact status and stress state around the fastener hole as the joints are under load and then increases the load capacity of the joints; secondly, too large preload or interference fit will cause joints to fail prematurely and decrease the load capacity consequently; thirdly, the effect of the bolt-hole fit conditions and the effect of the bolt's clamping forces impact each other, and these two parameters need to be considered together in order to obtain the optimized joint configurations.