Study on the effect of geometric errors of CFRP connection holes on the tensile strength of bolted structures

In this study, the effects of geometrical errors of CFRP countersunk bolt connection holes on the tensile strength of the connection structure are investigated. In order to obtain the stress distribution of the joint structure, the constitutive model of TC4ELI titanium alloy was developed by quasi-static experiments, and the material model of CFRP was established by combining the Hashin failure criterion and the bilinear constitution for the material interface. On this basis, a finite element model of the composite countersunk bolt joint structure was developed, and numerical simulations and experiments were conducted to verify the effects of three major hole-making errors on the mechanical properties of the bolted joint. The results showed that the proposed finite element model can accurately predict the failure pattern and tensile strength of the bolted joint. Secondly, the geometric error of countersink depth has the most significant impact on the final maximum stress value of the jointed structure compared to the error of countersink angle and fillet radius. Meanwhile, the influence of the upper and lower deviation of the countersink hole size on the tensile properties of the bolted joints has an obvious diversity.