Progressive damage numerical simulation and damage mechanism of steel/CFRP adhesive-woven hybrid lap joints

Carbon fiber reinforced polymer (CFRP) has attracted increasing attention as a novel material for ultra-deep oil drilling pipes. The lap joint performance between steel connectors and CFRP tubes is a key scientific issue. Based on the previous experimental work, a finite element model of steel/CFRP adhesive-woven hybrid lap joints was established by incorporating cohesive zone damage and the three-dimensional Hashin failure criterion, and the validity of the model was verified through experiments. Based on this model, the effects of the weaving width and the hole spacing on the mechanical performance of the joints were systematically investigated. Furthermore, the effective stress and the damage propagation rate were introduced to analyze the damage mechanisms. The results show that the influence of increasing the woven width on the joint performance exhibits a trend of first enhancement and then weakening, and 25 mm is the optimal woven width. As the weaving width increases from 10 mm to 25 mm, the damage propagation rate decreases, and the effective stress decreases from 10.80 MPa to 2.01 MPa. Meanwhile, the first and second peak loads increase by approximately 328.14% and 326.98%, respectively, and the failure displacement is delayed by 0.43 mm. When the woven width is further increased to 30 mm and 35 mm, the local stress concentration effect is intensified and the damage propagation is accelerated. Increasing the hole spacing also enhances the load-bearing capacity. As the hole spacing increases from 5 mm to 20 mm, the first and second peak loads increase by approximately 66.67% and 32.91%, respectively. The superposition effect of stress fields around the holes is weakened, and the effective stress decreases from 2.08 MPa to 1.84 MPa. The multi-stage cooperative load-bearing behavior and intrinsic damage mechanisms of the adhesive-woven hybrid joints are revealed, providing theoretical guidance and parametric support for the design of lightweight connection structures in oil drilling pipes.