An improved 3D model of composite bolted joints with detailed thread structure and progressive damage analysis of realistic tightening process

Bolted joint is a common connection method in composite structure assembling. The initial assembly state has a significant influence on the subsequent performance. To realize the simulation of the assembly process of composite bolted joints, an improved 3D model is proposed. This model considers the detailed thread structure and can be used to simulate the realistic tightening process. The relationship between the tightening torque and bolt tension is analyzed and the effect of the friction coefficient on the value of the tightening coefficient is analyzed using this model. A new fitting model for the nonlinear pressure distribution state on the outer surface of the composite laminates during the assembly process is proposed. And a quantitative analysis and prediction method of the nonlinear pressure distribution state is established. Finally, the effects of bolt tension and washer type on initial assembly damage are analyzed and experimentally verified.