Influence factors and testing fixture of bolted-joint composite laminate structure

To improve the reliability and carrying capacity of the bolted-joint composite laminate structure, we developed a macro-micro multi-scale numerical model that combines the improved general unit cell model (GMC model), based on ABAQUS and its user subroutines. We used this model to analyze the factors influencing the bearing strength of the bolted-joint composite laminate structure with respect to its mesoscopic composition material. The model results show that the failure mode of the quasi-isotropic bolted-joint composite laminate structure is extrusion failure and its crushing strength is high. In addition, the crushing strength of the bolted-joint composite laminate structure increases with increases in the width-to-diameter ratio (W/D) in bolted-joint structures that have the same edge-to-diameter (E/D) ratio. When the bolt pre-tightening force is 4.2 N·m, the bearing strength of the bolted-joint structure reaches a stable value. The bearing strength of the bolted-joint structure is improved by a proper interference fit. In addition, the thickness of the testing fixture should not be less than 3 mm and the diameter of the convex plate located inside the testing fixture should be two times the diameter of the hole in the composite laminate.