Numerical Study on Local Reinforcement and Damage Behavior of BFRP Bolted Joints

ABSTRACT To enhance the load‐bearing capacity of composite bolted joints while minimizing the weight and simplifying the manufacturing process, a local reinforcement design is proposed involving the embedding of composite sleeves within the bolt‐holes. This study focuses on single‐bolt double‐lap joints of basalt fiber reinforced polymer (BFRP) laminates, evaluating the enhancement effect of the embedded sleeve. To achieve this, the damage evolution process of the joint under tensile loading is characterized using a three‐dimensional Hashin failure criterion, an energy‐based stiffness degradation model, and a cohesive zone model. Furthermore, the influence of characteristics of the sleeve, including dimension, fiber volume fraction, and fiber type, on the mechanical performance of the joint is discussed in detail. It is found that the BFRP sleeve can effectively retard the initiation and propagation of damage, thereby significantly enhancing the ultimate strength of the joint without imposing an additional weight penalty on the original structure. Measures, such as increasing the sleeve dimensions, elevating the fiber volume fraction within the sleeve, or substituting the BFRP sleeve with a carbon fiber reinforced polymer (CFRP) counterpart, all contribute to an improvement in the joint's strength. Based on the parameters adopted in this study, when the outer diameter of the sleeve is 19 mm and CF volume fraction of the sleeve reaches 60%, the ultimate load of the joint increases by 44.7% compared to the unreinforced configuration. These findings offer new insights for enhancing the reliability of composite bolted joints.