Effects of countersunk hole’s geometrical deviation on the strength of bolted carbon fiber–reinforced plastic/polymer metal joints under tensile loading

Countersinking process introduces variations in the angle and depth of the countersunk hole due to the wearing down of the drilling bit and the specific properties of carbon fiber–reinforced plastic/polymer part. The ultimate tensile strength of the countersunk bolted composites is affected by the countersinking depth and angle. The article presents a numerical and experimental investigation on the effect of countersinking depth and angle on the tensile strength of the single-bolted countersunk joint. Numerical bolted models with designed depths and angles are constructed to predict the tensile strength. Nine experimental specimens are fabricated according to the ASTM-D5961 standard, and the experimental results validate the proposed numerical models. Analysis of variance is used to investigate the synergistic effect of the countersinking depth and angle on the ultimate tensile loading. The analysis of variance result shows that the countersinking depth should be strictly controlled. The relationship between the tensile strength and the depth of the countersunk hole is obtained by the validated numerical models, and the relationship could be used to allocate the tolerance of the countersunk holes. The reported work provides reference for precision countersinking in the composite bolted joint and help systematically in improving the precision strength prediction of the countersunk bolted joint in composites.