Effect of countersink geometric deviation on tensile strength of CFRP interference single lap joint

The countersunk bolt is widely used in aircraft bolt connection because it can satisfy the requirements of aircraft aerodynamic shape and reduce the radar reflection area. However, the countersunk bolt is affected by the geometric error of countersink and assembly error in the assembly process, which directly affects the joint strength of composite structure. The tensile strength of the composite structure of the countersunk bolt is affected by the countersink depth, angle error and nail pressing method. In this paper, the effects of sink depth, countersink angle error and nail pressing method on the tensile strength of single-bolt single-lap sink interference joint were studied by experiments and numerical methods. Nine experimental specimens are fabricated according to the ASTM-D5961 standard. According to the comparative analysis of experimental and simulation data, the results indicate that the oblique pressure connection should be better than the direct pressure connection; The ultimate strength of the joint increases with the increase of the countersink angle deviation; the increase of countersink depth error leads to the decrease of tensile ultimate load of joint; The ultimate tensile strength of the joint decreases with the increase of the angle of the deflection direction of the angle error, and the angle error of the countersink should be controlled within 1°. The empirical formula of the influence of countersink geometric error on the ultimate tensile strength of the interference connection structure of composite countersunk head bolts is established, which provides a reference for improving the connection strength of composite head bolts in engineering applications.